i have a 1968 factory air SS the I just bought previous owner told me it locked up on him this summer while car was parked with air on so he just cut belt ,how do i know if compressor (whole unit) bad or is it possible just clutch is bad ,how can i verify? also where is high side port on these ?
how do i know if compressor bad
speedydog5
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i have a 1968 factory air SS the I just bought previous owner told me it locked up on him this summer while car was parked with air on so he just cut belt ,how do i know if compressor (whole unit) bad or is it possible just clutch is bad ,how can i verify? also where is high side port on these ?
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If the pulley spins freely without any rough spots, then the bearing is OK. Put a 9/16" socket on the nut at the front of the compressor and turn it over. If it turns smoothly, then the compressor is OK.
The high side charging port is on the muffler on the discharge pipe from the compressor, low side is on the POA valve at the evaporator box plumbing.
BillL
The high side charging port is on the muffler on the discharge pipe from the compressor, low side is on the POA valve at the evaporator box plumbing.
BillL
You shouldn't need a wrench. Turn the front hub by hand and feel for binding or rough spots.
You can do a basic check on the valves and internals by disconnecting the manifold from the back of the compressor, holding your finger over the ports and turning the front hub in the proper direction. It should create pretty good vacuum on one and pressure on the other.
This is assuming that the system is empty, of course! Be sure to check for pressure before disconnecting the manifold! You'll probably find the system empty due to a leaky compressor shaft seal, though.
If it locked up from sitting and started to burn the belt, it's likely the pulley bearing. Parking it with the AC "on" won't do anything to the compressor. The AC clutch turns "off" when the car is off.
You can do a basic check on the valves and internals by disconnecting the manifold from the back of the compressor, holding your finger over the ports and turning the front hub in the proper direction. It should create pretty good vacuum on one and pressure on the other.
This is assuming that the system is empty, of course! Be sure to check for pressure before disconnecting the manifold! You'll probably find the system empty due to a leaky compressor shaft seal, though.
If it locked up from sitting and started to burn the belt, it's likely the pulley bearing. Parking it with the AC "on" won't do anything to the compressor. The AC clutch turns "off" when the car is off.
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i was able to turn by hand, so i put belt back on, started up and it started to cool great i added a can of oil to system , (just in case that was problem , but then the clutch locked up again wondering is it possible clutch is bad and how or can i change it?
How much oil did you add?. It is possible to hydraulic lock the compressor.
Also you high side pressure may be too high due to restricted air flow over the condensor. If there is no high pressure safety switch. this can also cause the compressor to lock up.
Also you high side pressure may be too high due to restricted air flow over the condensor. If there is no high pressure safety switch. this can also cause the compressor to lock up.
Adding oil to the system was a mistake, although it's a common one and easy to make. How much oil was in the can?
Your A6 compressor has an oil sump, much like a small 4 stroke engine. Very little oil actually travels through the system.
Modern systems, since about 1978, use sumpless compressors and the oil circulates with the refrigerant to lube the compressor. Kinda like a small 2 stroke engine. This is the system that almost everyone is familiar with today.
Since the compressor had locked up before, it's doubtful that you adding oil would have caused it to lock up this time. I agree with coldog, you probably have poor condenser airflow or something else causing the discharge pressure to soar and stall the compressor. Don't run it any more like that or you will damage the compressor.
That's actually a good sign in a way. It shows that the system is intact, the compressor is likely good, and it's basically "alive".
It's time to round up a set of gauges and check the pressures. It's possible that the clutch is just weak, but there's no way of knowing until you see what the High Side pressure is doing. You will eventually need to address the oil that you added, but that will come later.
Your A6 compressor has an oil sump, much like a small 4 stroke engine. Very little oil actually travels through the system.
Modern systems, since about 1978, use sumpless compressors and the oil circulates with the refrigerant to lube the compressor. Kinda like a small 2 stroke engine. This is the system that almost everyone is familiar with today.
Since the compressor had locked up before, it's doubtful that you adding oil would have caused it to lock up this time. I agree with coldog, you probably have poor condenser airflow or something else causing the discharge pressure to soar and stall the compressor. Don't run it any more like that or you will damage the compressor.
That's actually a good sign in a way. It shows that the system is intact, the compressor is likely good, and it's basically "alive".
It's time to round up a set of gauges and check the pressures. It's possible that the clutch is just weak, but there's no way of knowing until you see what the High Side pressure is doing. You will eventually need to address the oil that you added, but that will come later.
BTW. Your system is quite a bit different than the AC system on a ~1978-newer car.
Your AC uses what's called a POA valve (being a 68, it could be an STV), along with an Expansion Valve and a receiver/dryer. It's an excellent system that would put simpler, modern systems to shame. Properly repaired, it will still outperform all but the newest vehicle AC systems.:yes:
Look around here on TC and on other GM related forums for posts about pre-1972 AC systems. There's a ton of good info about testing and repairing your POA/TXV (Frigidaire-Harrison) system.
Another excellent source of information, especially if you are unfamiliar with AC in general, is www.autoacforum.com . It's a Newbie/DIY friendly forum that is sponsored by ACKits.com. Many of the regular posters are AC professionals. There is also a bunch of really good, POA/TXV system specific info in the Procedures, Tips and FAQ section. (it's a bit unorganized, so the search function is your friend).
AC systems are about the most misunderstood systems in any vehicle, second only to Electrical systems, IMHO. However, with a little knowledge and access to some, albeit expensive, special tools they are probably the easiest to repair. You usually don't even need a jack and the special tools are often available for rental.
Hope this helps, at least a little.
Your AC uses what's called a POA valve (being a 68, it could be an STV), along with an Expansion Valve and a receiver/dryer. It's an excellent system that would put simpler, modern systems to shame. Properly repaired, it will still outperform all but the newest vehicle AC systems.:yes:
Look around here on TC and on other GM related forums for posts about pre-1972 AC systems. There's a ton of good info about testing and repairing your POA/TXV (Frigidaire-Harrison) system.
Another excellent source of information, especially if you are unfamiliar with AC in general, is www.autoacforum.com . It's a Newbie/DIY friendly forum that is sponsored by ACKits.com. Many of the regular posters are AC professionals. There is also a bunch of really good, POA/TXV system specific info in the Procedures, Tips and FAQ section. (it's a bit unorganized, so the search function is your friend).
AC systems are about the most misunderstood systems in any vehicle, second only to Electrical systems, IMHO. However, with a little knowledge and access to some, albeit expensive, special tools they are probably the easiest to repair. You usually don't even need a jack and the special tools are often available for rental.
Hope this helps, at least a little.
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i do understand a hvac system as i have been a hvac tech for 20 years, one bad thing on this system for whatever reason when it was restored, there is no high side port anywhere not on the muffler of discharge either ,and i only added a couple ounces of oil at most i noticed that sight glass was still flashing when it was running but when i started it up it was cooling great, i,ll try and put my gauges on but i,ll only get to low side,unless i buy a new muffler with a discharge port, but my question still is if it is the clutch can that be replaced?
Oh! You know HVAC. That's good.
Most times, folks posting here have little/no AC knowledge so I tend to start on the ground floor.
The clutch on your A6 compressor is replaceable without recovering the system. However, finding a clutch kit may be an issue. Most automotive parts suppliers don't list them anymore. You may need to look toward HD truck, RV or AG suppliers for a clutch kit. The A6 wasn't used on cars after about 1978, but it saw a lot of use in other areas all through the 90s.
Edit: Knowing HVAC, you DO know how important knowing the High Side pressure is, don't you? There almost HAS to be a port somewhere between the compressor and TXV. If not, somebody sure screwed up
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