Hey guys Id like to pick your brains on an A/C issue Im having. I have a 72 Elco that I recently completed an LS swap.
Heres what I have:
original evaporator
new expansion valve
Old Air POA upgrade
r134a
denso 10s20f compressor
parallel flow condenser
trinary switch fed 12v from Old Air TCS switch(compressor on a relay and dual electric fans)
Heres what I don't have:
Comprehensive knowledge of A/C systems to diagnose problems
Heres whats going on:
Since this is an oddball system I have no exact numbers on how much to charge it so I went by the pressure chart. The problem I had with that is the pressures rise and fall with the fan turning on/off and the compressor on/off. I didn't know what pressure I was looking for. If I brought the rpm up to 1500ish the high side would go to almost 400 and it seemed like the low side didn't gain much pressure past 35 as I charged it. So I charged it as best I could and it was working pretty good. It was blowing 45deg about 80% of the time. Occasionally I would lose cold air for about 20 seconds when accelerating from a stop. I was afraid I may had overcharged it so I didn't use the AC much until I had a shop look at it. I took it in and they said I had overcharged it by about 8oz, they recovered the excess and told me to give it a try. The AC hardly works now. It generally works at idle and cycles from warm to cold at cruising. The shop thought that the trinary switch I put in was for r12 and was letting the compressor run way too high. The switch is for r134 and I cant find any switches available that would cut the compressor at a lower pressure. The high cut off pressure for all of them seems to be 375-400. The only thing I can think of is the expansion valve is not correct for my system and is not allowing proper flow? Like I said A/C is not my strong point. I get the basic concept of it but not much beyond that. Hopefully this post makes sense and If I can clarify anything I will do my best to do so. Thank you!
You wrote "fan turning on/off". I presume you mean the electric fans behind the radiator? If yes, the compressor head pressure is going to go high when the fan(s) is off because no heat is being removed from the condenser.
What happens when driving down the road with the AC running? My guess is better performance because driving airflow is removing condenser heat.
No heat or AC yet for me but I will wire my 70 EC so that any time my AC is on both of my Cold Case radiator fans will also be running. I can easily do this because my E-fans are not controlled by my LS powertrain control module - the fans have a separate controller. This is the Four Seasons part number 35879 that has a blue wire for use by the air conditioning system to turn on fan power anytime AC is running.
Here is what I know. I have a 70 with a 468 B.B. I converted my system to R-134. FIRST: R-134 has a different expansion rate than R-12. When the Comp. is engaged the P. Flow condenser NEEDS AIRFLOW.
If you can not COOL DOWN the R-134 with the cond. you will have issues.
This is what I have in my 70, Alum. 10 Cyl. R-134 compressor, From the Fla. Guys. Same parts as you have. POA, adjusted for 134---P. Flow Condenser built for a 70-72 (uses all org. nuts bolts & brackets) 134-dryer.
I also have the 4 row copper /brass rad. ( Standard cooling system for a 70-72 with A/C. My fan blade is a 3947772 on a clutch. My engine temp never goes over 185 / 190. NOTE: VERY IMPORTANT--- A factory C-60 system takes a R-12 Charge of " 60 OZs " When you convert to the R-134 system with all the correct parts. The R-134 has a VERY DIFFERENT EXPENSION RATE than R-12.
Using the R-12--60 Oz. when you convert you use the 80% RULE, What the HELL is the 80% RULE????
80% of the 60oz = 48 OZs. Put it in simple terms. Charge your system with " 48 " OZs of R-134......... YES,,, Charge your system with 48 OZs AKA 3 LBS. of 134...... Dont even look at the gauges, Just shoot it up with 48 OZs of R-134..
I just tested my converted system yesterday, I am getting 38 to 40 degrees out of the center vent in my 1970 FRAUD SS 468 Nomad Sta. Wgn.
Bottom line when the Comp. clutch kicks in,,, You need a " TON " of air going over the P. Flow Condenser.
I am leaving for the OHIO Chevelle show at 8:00 AM in the Morn.
REMEMBER- 48 OZs of R-134 NO more NO less for a 60 OZ. G.M. system .
80% of the factory R-12. Due to the fact, R-134 has a VERY different expansion rate, OR it runs a lot hotter than the R-12. Suck it out and SHOOT it up with 48 OZs of R-134. Remember LOTTSA AIR over the Cond.
Bob
The above information is for 69-72 Chevelles. I also have a 70 El Camino SS 454 /M-22 that I ordered in Feb. of 70. I will get back to you on Monday!
Did you install a new reciever/drier and vac the system down before charging? If you did not do this, then stop now and start over.
Did you add oil to the compressor and drier before recharging?
What was your POA valve pressure set at?
On a 72, there's a temp switch mounted to the outside of the a/c suit case that disengages the clutch. Has this been incorporated into your clutch control circuit?
Why are you using a TCS switch?
Your system is not a cycling system. That high pressure switch is there to cut power to the compressor only if high pressures are detected. 400 PSI IS WAY OVER THE LIMIT for safe operation on 134a at just about any ambient temp we're bound to experience. Your high pressures are all over the place because you did not cool the evaporator and run up the rpm to 1500 rpm. Another reason for high pressures is a blockage in the system.
The compressor should keep running 100% of the time that the a/c is on. There's also a low pressure switch that does just the opposite, when there is low pressure it shuts down the system to protect it from running when pressures are too low. The thermal switch cuts power to the compressor to control evaporator freeze up.
Your entire issue maybe that your fans are not on when the compressor is on. Lack of cooling of the condenser will send your high side pressures sky high and result in no cooling. You also over charged the system because your rpms should have been 1500 rpm while charging and you should only charge your high side according to the corresponding mid point of the pressure chart. Use the pressures on the chart according to the measured ambient temp.
You need to start with a good ambient temp reading. Wire up your cooling fans to turn on anytime the compressor kicks in. Later you can modify your fans to come on anytime your high pressure is over 180 psi to 225 and stay on at psi over that. Put a large fan in front of the radiator. Charge or recover refrigerant until you are in the mid range of the pressure range of the pressure chart for the corresponding ambient temp. Disregard your low pressure and charge per the high pressure reading.
After that's done, what is the ambient temp, high and low pressures, and temp out of the center vent? Are you pressures stable? If it's not cool and stable we have other issues. The gauges will tell the story.
The expansion valve and POA valve are what determine your low pressures. Your POA valve should have been set at 26 psi. A POA Valve prevents the evaporator from freezing by by-passing excessive system pressure. It's what allows the clutch to remain on all the time the a/c is running.
Here are some pictures of what I'm working with. As you can see the system has been changed to work with the ls motor. Is it possible the POA is not functioning properly?
Yes it has a new reciever drier. Tonight I'm going to try bypassing the thermal cycling switch and run the fans/compressor strictly off the trinary switch and see what this does.
That's not a POA valve. That's a POA valve eliminator. Your system is now a clutch cycling system controlled by the clutch and switches. Technically, you don't have a POA valve and there is nothing in the POA valve eliminator valve that can malfunction.
Compressor cycling is controlled by the switch on the POA valve eliminator. If there is a high pressure switch in the system, and there should be, it's only function is to protect the compressor from high pressure. It's not actually used for cycling.
Set a fan in front of the condenser, engine at 1500 RPM, electric fans on, check your pressures. You may still be over charged. Use the line that corresponds to the ambient temp on the pressure chart. Get your high pressure in check first. My current guess is that the a/c shop set your high pressures in line with the ambient temps, but did not adjust the cycling valve on the low pressure side.
Then adjust the clutch cycling switch on the low side to 26 psi. Check your temps and pressures again and the temp at the output vent. Classic Air says to set for 21 psi, You might have to play with this and turn it down towards 21psi, The lower you go the cooler the temp, but you risk freezing up the evaporator. would stop lowering the psi at about 40degrees outlet temp,. If you hook up the thermo switch in the a/c suit case, you'll be able to run a lower psi because it will prevent freeze ups by also cycling the compressor. It should be run through a relay so the thermo switch doesn't take all the amps at it's contacts.
If your heater hoses are hooked up, use a valve or hose clamp plies to close the flow to the heater box.
Read the PDF, you can follow the instructions in it.
When you get your pressures and temps post them up.
Last picture is the a/c thermal switch mounted in the a/c suit case. Monitors temps in the evaporator box to prevent freeze up. There's another in the same area, thats the blower motor resistor. You can see the bmr in the upper right of this picture. These are located in the engine compartment.
I just took some readings. All were taken with the motor at 1500rpm. Ambient temp of 80f
High side: 210psi with fans on compressor on and box fan in front of the condenser. The chart says 175-210
Low side: compressor off at 25, on at 49. That is the range of pressure I observed.
The coldest air I saw was 54f. The cold air comes when the compressor is on and goes away quickly when it is off.
I jumped the cycling switch on the POA ELIMINATOR(thank you for the education!) the low pressure ranged from 17-22 @1500 and the high stayed at 240-245. cabin temp got down to 43f but I noticed frost forming on the evaporator tube so I stopped what I was doing.
I have my pressure switches wired as follows: 12v from the original AC relay to the cycling switch to the trinary switch( located on the rec/dryer as shown in the pic) to the compressor(relayed).
Hopefully this gives a little more information, I have a tough time understanding mechanical things by written words alone
You're still over charged. You should be running both fans on full for this phase with your pusher box fan in place. Recover some refrigerant until you get your high pressure down to about 200 psi. If you come out lower that's fine. No lower than 185. We may bump this up slowly later to peak cooling performance. I like to work at it from the lower pressure and add as I Watch system performance. By running a lower pressure here, you'll have less cycling of the compressor and a more constant flow of cool air. This is one of the pressures you play with to get a happy system when you use the POA valve eliminator.
So we want to drop that high pressure down, then adjust your cycle valve on the POA valve eliminator to show a minimum of 24psi psi. (We'll try it there, It's between the 26 I usually use and the 21 Recommended by vintage air.) You'll turn the adjusting screw to the right a full turn, then connect the cycle valve and check your low side pressure. For now, we want the low pressure to stay at or above 24 psi. (with r134a, your evap would freeze at 28 psi, but we lower the pressure to account for the air movement through the evaporator. This is another pressure we adjust for maximum performance. Every system is a little different, so hard numbers are hard to advise)
It's not unusual to see frost on the evap tube, so don't let that scare you too much. If your outlet temp is above 38 degrees, your not freezing the evaporator.
We'll work on your electrical system, like you I need to think about what you have going on. We'll try to incorporate the temp sensor switch in the evap box to prevent freezing under certain conditions.
You're still over charged. You should be running both fans on full for this phase with your pusher box fan in place. Recover some refrigerant until you get your high pressure down to about 200 psi. If you come out lower that's fine. No lower than 185. We may bump this up slowly later to peak cooling performance. I like to work at it from the lower pressure and add as I Watch system performance. By running a lower pressure here, you'll have less cycling of the compressor and a more constant flow of cool air. This is one of the pressures you play with to get a happy system when you use the POA valve eliminator.
So we want to drop that high pressure down, then adjust your cycle valve on the POA valve eliminator to show a minimum of 24psi psi. (We'll try it there, It's between the 26 I usually use and the 21 Recommended by vintage air.) You'll turn the adjusting screw to the right a full turn, then connect the cycle valve and check your low side pressure. For now, we want the low pressure to stay at or above 24 psi. (with r134a, your evap would freeze at 28 psi, but we lower the pressure to account for the air movement through the evaporator. This is another pressure we adjust for maximum performance. Every system is a little different, so hard numbers are hard to advise)
It's not unusual to see frost on the evap tube, so don't let that scare you too much. If your outlet temp is above 38 degrees, your not freezing the evaporator.
We'll work on your electrical system, like you I need to think about what you have going on. We'll try to incorporate the temp sensor switch in the evap box to prevent freezing under certain conditions.
So before I read your latest reply I dropped the cycling switch down to 22psi. This resulted in about a 15% improvement. Previously I had about 50/50 cold/warm mix when at cruising speed. After dropping the shut off pressure to 22psi from 25, this improved to 65/35 cold/warm cruising with a vent temp range of 45-60.
I evacuated the high side. The ambient temperature went up to 82 so I evacuated to 195psi. I now have a 40/60 while cruising and vent temp ranging from 50-70. It just seems the only way I get cold air constantly is if I overcharge the system
Did you evacuate the system prior to charging. Too much oil, moisture, or air in the system will reduce cooling temps.
Take a look at your sight glass, are you seeing any streaking or bubbles with the a/c on?
Your system is showing signs of a faulty expansion valve. Your vent temps are no where near where they should be, But we can check a few other things.
A blockage might cause an issue, showing as high pressure on the high side. Run your hand or temp gun over the line from the compressor to the condenser, over the condenser to the expansion valve. Look for frosting or areas where the temp goes from high to low. If you find one, there's a blockage at that point.
You may have an air flow issue through the condenser. Electric fans not pulling enough air while standing still. You can spray water on your condenser then check pressures. IF low, add refrig back to your chart levels. Or, leave the gauges hooked up out the back of the hood, duct tape to window then go for a ride and get some pressures while cruising down the road. If your high side pressures are low when cruising your charge can be increased. Then you have to increase air flow to your condenser. But if they are bouncing to max pressure then you'll have to start over, replace the TXV valve. re- evacuate the system and I would install a new drier.
Dutch I just want to say thank you for helping me with this and getting back to me so quickly. Yes I pulled vacuum for at least 30 minutes and it held 29in for another 30 after before I charged it. I will go over the lines tomorrow and look for temperature changes. The AC system worked great before I did the ls swap. It is a new expansion valve but it has a different sensing bulb than what was on prior to. It had the curly pig tail style and now it has the long flat bulb. This would not be the first nor the last time I've had brand new parts be faulty. It's also very possible something is plugged up. Thank you again I will report back tomorrow
I'll wrack my brain some more and see what I come up with. Like reading technical stuff, trying to put into words a technical topic is difficult. It's so much easier and faster to be there and do it in person.
Check the equalization in the morning or when you get a chance. Before you start the car note the ambient temp and gauge readings. Start the car let the pressures build. Then shut off the car and watch your gauges. They should equalize within a few minutes. You can actually watch the low pressure side rise and the high pressure side drop as the high pressure moves through the expansion valve to the low pressure side. If it doesn't equalize within a couple of minutes the expansion valve is not functioning correctly. If it's not moving you can take the bulb loose and hold it in your hand or hot water. If the pressure the drops, your expansion valve is bad and needs to be replaced. Sometimes this will free a stuck valve, but the fix is usually temporary. There's a screen in the front of the expansion valve that can become plugged. Check for this if you pull the expansion valve. Hopefully it's clean.
This seems to make the most sense. If the expansion valve is faulty the only way the AC can function is with such a high charge that it forces its way into the evaporator. I will check in the morning before work. Thank you again!
Heres what I got this morning. I started with an ambient temp of 64 and both sides being at 70psi. started and ran the ac for a few minutes then shut it off. It has been 5 minutes since I shut it off, the low side is at 48 and the high is at 120. It looks like it will take probably an hour to equalize at this rate. The sensing bulb is wrapped up pretty good on the evaporator so I took a heat gun and warmed it up, the pressure(starting at 52 and 115) equalized to 70 within about a minute by doing this. Would it be safe to say the expansion valve is no good?
A receiver drier is under 20 bucks, Replace it too for good measure. The one I use are shipped with oil, your's may not be, so may have to add oil.
Before you tear down, run the system and check the sight glass. Do you see any oil streaking in the glass. Oil and air are non condensibe, Too much oil or air in the system will degrade performance. Also, if you have a heat gun, run it over the tubes of the condenser and lines of the high side. Look for any cool spots or frosting. Let's eliminate that as a possible source of restriction as best we can before you proceed.
Below is a PT chart for both r12 and 134a. It's difficult to rely on because temps must be equal throughout the system and gauges and thermometers typically have a tolerance or are out of calibration. But it is a good tool for the box. It can give you hints.
The PT chart also shows you the pressures of the refrigerant at freezing. From it you can deduce the reason for setting your pressure switches and/or POA valves for a specific temperature. We usually set the pressure lower, because the air flow and inefficiency of the coil allow us to run a lower setting without freeze over of the evaporator. GM added a temp control switch in the suitcase to help prevent freeze over. It's not there to be used as a cycling switch.
R134a At 400psi is around 182 degrees. Is the condenser in front of the radiator? Is the radiator shrouded?
The fan should be on when the air runs.
Could be air in the system. Could be over charged.
Air in system is easily checked when car is cold you will need ambient temperature outside and a pt chart for 134a. The pressure/temperature will match. Air in the system the numbers will read high.
His high pressure is high, his low too low. Poor cooling: Indicates a blockage on the high side, faulty expansion valve, possible air or too much oil in the system, and an indication of poor cooling most likely due to air flow through the condenser.
All of which should be addressed when he installs a new drier, expansion valve, evacuate the system, and recharge the system. The lack of cooling of the condenser most likely due to insufficient air flow will still need to be addressed if his high pressures can't be held in controlled. At this point we need to get it charged to diagnose this issue.
What did I miss? Seriously I welcome all replies. I'm just here to help my Chevelle Bro's.:grin2:
Ok the expansion valve is ordered and I have an extra drier ready to go. I'll check the sight glass and high side lines tonight and see if there are any blockages.
Hook up your fans so they are on when the a/c is on regardless of whether the clutch is engaged. This Will help cooling and help lower pressure spikes when the clutch reengages...I think.
Just rambling below....sort of free thought.....giving ideas....going crazy?:wacko:Rambling to avoid real work.>
You are already at a handicap...I think...since you are using electric fans. We'll have to see what your pressure do. Sealing the condenser to the radiator with foam or weather striping would force the fans to pull thorough the condenser. We can add a pusher fan to the condenser, but it actually adds a resistance to flow to the radiator in many cases and if you are already at capacity on the cooling system this could cause over heating issue. Sometimes the pusher help in engine cooling. It's a YMMV type of thing.
If you don't own a temp gun, they are worth having. Not just for this but many other uses.
Hook up your fans so they are on when the a/c is on regardless of whether the clutch is engaged. This Will help cooling and help lower pressure spikes when the clutch reengages...I think.
Just rambling below....sort of free thought.....giving ideas....going crazy?:wacko:Rambling to avoid real work.>
You are already at a handicap...I think...since you are using electric fans. We'll have to see what your pressure do. Sealing the condenser to the radiator with foam or weather striping would force the fans to pull thorough the condenser. We can add a pusher fan to the condenser, but it actually adds a resistance to flow to the radiator in many cases and if you are already at capacity on the cooling system this could cause over heating issue. Sometimes the pusher help in engine cooling. It's a YMMV type of thing.
If you don't own a temp gun, they are worth having. Not just for this but many other uses.
I do have the heater hoses hooked up and functional I can run up to harbor freight and grab some hose Pinchers to get a better feel for what's going on.
I checked all the high side lines and hoses to find any cold spots and it all was hot to the touch. I checked it with my temperature gun as well. When I ran the AC 5 minutes ago the fans stayed on the whole time whereas any time before they cycled on and off. It could be because it's hot out and the car was sitting still in the sun, I'll look into it later tonight .
The sight glass looked ok I didn't see any large bubbles or oil but I can't say I really know what I'm looking for when it comes to that part.
Everything but the evaporator and POA eliminator is brand new and was not opened until I installed them including the compressor and condenser. Both of these came from the factory pressurized and the compressor had 8oz of pag46 which is the correct oil type and capacity. I had issues with my hose crimper(instructions said one thing, the companies video on YouTube said another, I went with the instructions and lost) and had to take all my hoses off and recrimp them after I charged the system. I added 1oz of oil at this time due to the many leaks I encountered. According to denso you can add up to 2 oz before you're overfilled so I played it safe.
The evaporator and POAe were open and exposed for a few months so it's entirely possible some contamination started there and made it all the way to the expansion valve screen?
I did put the reciever in dry(AC novice ignorance) but after the hose leaks, I did add 1oz of pag46 directly into the compressor hopefully this will compensate for any oil that migrated to the reciever. When I put the new receiver in I will add a little oil to it this time. Question: if I were to pull the compressor and dump the oil and start from scratch with a new reciever, how likely would it be that there will be oil still remaining in the system. I would like to evacuate everything and start from scratch with a new expansion valve and receiver but I don't have the equipment (I think) to do a proper job. I have manifold gauges and a ventrii vacuum pump.
What a trip. I've never used a venturi vacuum pump to pull down an a/c system. I use them all the time at work, just not for a/c. I suppose it should work if you can pull 29 hg for more than half an hour as long as its hooked up to your gauges with both red and blue valves open. You can call a local auto shop and see if they loan vacuum pumps if you want to go that route.
The oil situation is a concern of mine here. Since we had an issue with flow through the exp valve, we may have a condition that's called oil logging. It's where the evaporator gets flooded with oil. It leads to poor cooling and exp valve operation because the tubes of the evap get coated in oil, which insulates the coil from the refrigerant.
You might want to flush the condenser to make sure it's not oil logged. When you pull the expansion valve, if you see oil pooled, I would recommend a flush then blow out with nitrogen or shop air. If you use shop air add some time to the evacuation cycle.
This part is where ******* engineering and figuring come into play as we now have a different compressor and condenser.
If you want to start over with the oil, drain the compressor and measure how much oil it contains. Since it was full when you started, the oil we're missing is in the system. We'll never know how much is or was in the evaporator since we can't remove the oil without removing the evaporator. Recovery or evacuation doesn't remove the oil. It removes small amounts which are collected by the machine and measured. Then we add that amount back to the system.
The Chevelle service manual says add 11 oz oil to the system. Unfortunately we're now dealing with a different system.
Figure the oil required for your system....The oil for the compressor + 2oz for the drier, 1 oz for the cleaned out evap, 1.5-2 oz condenser if you flush the condenser(just flush from in to out). If you don't flush it, don't add the totals. What's the total? I don't part number of compressor.
The Chevelle service manual says 60 oz of r12. BUT, when charging to r134a we charge to 80% of the r12 charge, So that's 48oz r134a. Approx 3 16 oz cans. Of course, we're dealing with a Franken system, but this will give you a close approximation.
Charge slowly and allow pressures to stabilize. You might be able to watch for bubbles in the sight glass. 134a is a bit cloudy and most 134 systems won't have the sight glass. But if we have one, we'll use it and our gauges to monitor charge level. It's normal to see a puff of bubbles when the compressor kicks in. Don't try to charge this out. Wait until the system stabilizes if your watching the sight gauge. The most important tool is the pressure gauges. Trust the gauge before the sight glass.
If someone has a better way to determine oil requirements for a Franken system, please post up. There's about a 2oz tolerance up or down for the oil. 2oz to little=shortened compressor life. 2oz too much = diminished cooling.
Be prepared to adjust you cycle switch. Classic air says 21, So shoot for that number and we'll see where that gets us.
Watch your high pressures. IF you spray water on the condenser and the pressures drop significantly, we'll have to work on the airflow.
Vacuum is not determined by time.
It’s a measurement done in microns.
Microns need to be 400-500 to prove a good vacuum and no contaminates remain.
29hg is around 30000 microns.
Rent a micron gauge.
Any moisture will move through the system and freeze as the pushes past the metering device(valve)
Not sure what post but OP put some pressure and temperature numbers up. That showed air in system and that increases the pressures.
From the numbers the op posted
400 psi 134a with low air flow on the condenser. You are not going to remove the heat. That will cause higher then normal evaporator temperatures Air flow need to be addressed.
As you removed refrigerant the pressures drop. But you didn’t address the air flow.
As refrigerant becomes low the compressor will not returning the oil though the system. It coats the evaporator and will not transfer heat properly. OP added a extra ounce of oil adding even more to the problem. The system needs to be flushed out.
A clogged metering device will cause low pressures on the low side with no capacity (no heat removal) and a normal high side pressure. The refrigerant will stack up on the high side and that subcools.
Your going to need to remove components and extra oil and flush with dry nitrogen.
Put the proper amount of oil in. Pull a vacuum with a micron gauge to prove no leaks and moisture is removed. Make sure you have proper air flow across the condenser. And recharge the system to factory spec if it’s 100% factory. R134a need to be charged at 80% of the r12 recommendation. As was mentioned earlier.
If your system isn’t factory you can’t charge like that you may need more or less. A good starting point would be 50% and slowly bring the high side up to what the manufacturer recommended. That only works if you have proper air flow.
Restrictions will cause a drop in pressure that will cause a drop in temperature. If a condenser was clogged inside. You would seen or feel a cold section.
When I had it overcharged to near 400psi at 1500rpm I had continuous cold air coming through the vents. Now that it is at the correct pressure, I do not have continuous cold air through the vents. The condenser was new and pressurized and was not opened until I hooked up the rest of the lines. If it's clogged contamination may have traveled to it but I can't find any cold spots on it
Harbor freight 16 bucks. It pulls 29 as long as your air compressor can keep up.
The compressor is a Denso 10s20f used in Silverado's. It was a brand new compressor I found on Craigslist. According to the Denso website all their compressors come filled with the proper amount of pag46 oil (8oz for this particular compressor). The compressor came with a metal/rubber plug on the ports and when I took it off it was pressurized so I know that it hadn't been tampered with. I measured out 1oz of pag46 and added it directly to the compressor after the hose fiasco. Now it is entirely possible there was residual pag150 in the evaporator left over from the original system. In hindsight I should have flushed the evaporator before I assembled the system. I'm thinking the best route to take is get the entire system flushed and change the expansion valve and reciever as well as dump the compressor oil and start from scratch. As far as flushing goes, do most shops have a way to flush the entire system easily or is this something that needs to be disassembled and parts flushed individually?
Read the directions on the can. Disconnect your hoses and run this flush through it. Let it sit a couple of minutes then put a little more in blow it out with shop air. Repeat the process one more time. Do this through all hoses, evaporator and condenser. You'll be fine.
Put a drop of oil on your o rings, reconnect your hoses and install your new parts. Do your drier last and when you are ready to start evacuating the system. Add your oil, PAG or ester type. Fill your compressor to it's required amount, 8 oz. Put the remainder of the oil in the drier. Pull a vacuum of 29hg for on hour. More time added because we used shop air. We want to boil out any moisture. I would prefer that you use an electric evacuation device. Not sure I trust the vacuum device you have, But if it pulls the vac as required, go for it. Your choice.
I think you may have a air flow problem at the condenser. We can still charge the system and address that. Watch your pressures while you charge. Don't let them exceed cart values at ambient temps. Charge slowly, let your temps and pressures stabilize as you add refrigerant. Purge your ac gauge lines before you hook them to your system.
You got this. If you feel better taking it to a shop, then do so.
When you remove the components you’ll need to remove the compressor to drain the oil. Measure the amount that comes out. Flush the system backwards (pressure up the low side with the high side open.)
How long did you run the ac with the high side at 400? You need proper air flow across the condenser. And the high side will be high when the ac first starts up as there is more heat being removed by the refrigerant. You also have air mixed into the refrigerant system that will cause a higher pressure. Boyle’s law I believe it’s is.
Example is a hundred psi cylinder of pure oxygen connected to a hundred psi cylinder of a different gas will read 200psi
This works just like that refrigerant mixed with air because your refrigerant is pure with no contamination (air/moisture) this will increase the pressure and take up condenser space inside the system usually the highest point.
That combination with the low condenser air flow is why you seen 400 psi on the high side with normal evaporator temps.
The metering device, don’t care about high side pressure(unless it is a contentious open like a cap tube style) or to low to keep a solid stream of refrigerant feeding into it.
The expansion style system will meter down.(close down) to keep the proper superheat at the evaporator.
Quick video of flush process. If you don't have the flush gun, the aerosol product I linked will do the job.
Wear eye protection and stay out of line of the tube when you pressurize.
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