EXPRESS 2500 AC Problem - Chevelle Tech
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post #1 of 14 (permalink) Old Aug 29th, 19, 8:48 AM Thread Starter
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rick
 
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EXPRESS 2500 AC Problem

My 05 Express 2500 w/4.8 litre has 150K mi. and ac works until it get above 90* outside then comp shuts off, I'm a res/light comm. ac cont. but don't know squat about automotive ac, it has plenty of refrigerant but power shuts off comp for some reason, I've swapped around micro relays & checked fuses then took it to a local shop to get "needs new shrader valve, ball valve, compressor, dryer "their spelling", orfice, o-ring, evac & recharge & labor $794.25 and seems fair but what's really shutting comp off? just trying to learn something before I have them do this and it has the same problem, TIA, rick.


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post #2 of 14 (permalink) Old Aug 29th, 19, 9:55 AM
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Re: EXPRESS 2500 AC Problem

Check for low air flow thru the condenser in front of the radiator. Clean it and check your fan clutch.

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post #3 of 14 (permalink) Old Aug 29th, 19, 10:32 PM
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Re: EXPRESS 2500 AC Problem

I have had good luck with Mancini Automotive for A/C repairs, if you get to New Port Richey, you might give them a call and good luck!!

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post #4 of 14 (permalink) Old Aug 29th, 19, 10:34 PM Thread Starter
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Re: EXPRESS 2500 AC Problem

I did replace the fan clutch about 3 weeks ago and chem cleaned the condenser, I should have added that in my post, it worked on and off today in 93-95* heat but not great which makes me wonder if comps bad why does it work at all ?


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post #5 of 14 (permalink) Old Aug 29th, 19, 11:05 PM
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Re: EXPRESS 2500 AC Problem

Hows your engine cooling temp? Running high? Some of these newer pos systems will shut down and leave you sweating if the engine temp reaches a certain point.

My 2005 Silverado wouldn't turn on the compressor, ened up changing the control head in the dash to get it working.

Hook up your gauges this weekend and check operating pressures. You could have a blockage/high-pressure situation or low charge, the only way you'll know is by gauge readings. You could also have a faulty low or high pressure switch or poor electrical connections to them.

The only way I can work through these newer systems is page by page in the manual. They are a pain in the butt. All the moons and planets need to align to get them to work.

If that a/c shop didn't pull out the ohmmeter and gauges, it sounds like they will throw the kitchen sink at it and see if something sticks. They'll do that just to find out that it's an electrical/module issue.
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post #6 of 14 (permalink) Old Aug 29th, 19, 11:20 PM
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Re: EXPRESS 2500 AC Problem

Control head is a good place to start, I had a 2005 F-650 that took me two years to finally get it working right, tried everything under the hood, driver told me that it worked fine in the AM going out the the jobsite, but when it was hot outside later in the day, the A/C hardly worked. I finally decided that the control unit in the dash was the only thing I hadn't tried, so I ordered one, installed it the next day and problem solved!!
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post #7 of 14 (permalink) Old Aug 29th, 19, 11:33 PM
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Re: EXPRESS 2500 AC Problem

You can check the signal from the control head. You can also check to see if the clutch is getting power to lock up. Check the pressure switches when it's malfunctioning by disconnecting them, them jumper the leads or put an ahm meter on them and check if they are open or closed. I started at the compressor and worked my way back into the elect system.

I had to go through the wiring diagram and a bunch of tests to see that the control head was not sending the signal to the a/c clutch to engage. First I checked all the pressure switches.

On mine, the green wire from the control head was not feeding power out, if I remember correctly.

If the clutch is engaged and you're not getting a/c, then the issue is charge or hardware related. These issues should be easy for a HVAC guy to repair.

Come on man, an HVAC van? You should be able to hang meat in there.
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post #8 of 14 (permalink) Old Aug 30th, 19, 6:40 AM Thread Starter
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Re: EXPRESS 2500 AC Problem

I'm going to check the control head and pres. switches sunday (if I'm not working) and let you guys know what I find, thanks, rick.
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post #9 of 14 (permalink) Old Aug 30th, 19, 5:42 PM
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Re: EXPRESS 2500 AC Problem

Rumor has it that Chevy's eat low-pressure switches. I've never been so lucky. If your clutch is kicking out, check to see if there is power at the clutch lead. The negative side of the circuit is controlled by the low pressure switch. So if there is power to the clutch, take a close look at the negative circuit. If your a/c charge is good, you can jumper the low side switch as a test.

Don't remember if the high side switch was on the neg or pos side of the circuit. I'll dig around and see what I can find.
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post #10 of 14 (permalink) Old Aug 31st, 19, 7:30 AM Thread Starter
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Re: EXPRESS 2500 AC Problem

One of the guys did unplug a wire and put a jumper wire in, looked like he took it from the low side, low pres. sensor wire? hope I have time to work on it tomorrow, it's been HOT


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post #11 of 14 (permalink) Old Aug 31st, 19, 1:14 PM
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Re: EXPRESS 2500 AC Problem

Quote:
Originally Posted by shovelrick View Post
One of the guys did unplug a wire and put a jumper wire in, looked like he took it from the low side, low pres. sensor wire? hope I have time to work on it tomorrow, it's been HOT
Don't you have a Hurricane to dodge headed your way?
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post #12 of 14 (permalink) Old Aug 31st, 19, 10:15 PM
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Re: EXPRESS 2500 AC Problem

Al, Rick and I are on the Gulf Coast, we'll get some wind and rain, but unless the storm changes directions, we should be ok!!

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post #13 of 14 (permalink) Old Sep 3rd, 19, 7:00 AM Thread Starter
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Re: EXPRESS 2500 AC Problem

I had some time yesterday but couldn't get it to stop working I guess since it was overcast and not too hot out? going to have a friend look at it asap


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post #14 of 14 (permalink) Old Sep 3rd, 19, 7:40 AM
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Re: EXPRESS 2500 AC Problem

I have had that problem with a couple Chevy trucks. I always blamed it on air flow thru the condenser. Any vehicle with electric fans always run full speed when you turn on the AC. The mechanical clutch fan spins slow at an idle. I wanted to try adding an electric fan but never could fit one in. Maybe you could use a laser temperature gun to measure the difference in temp between the input and output of the condenser when it is working and when it is not working.

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