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Help Needed 84 chevy truck

BigTruckDriver on Sat May 23, 2015 3:08 PM User is offline

Year: 84
Make: chevy
Model: c-10
Engine Size: 350
Refrigerant Type: r134
Country of Origin: United States

Everything in the system has been converted to use the r134 freon. The ac seemed to be working fine for a week but then I got a leak in the cold line. I bought a new cooling line and had it replaced . Now it blows cold but after sitting for awhile like in traffic it will blow warm. It will stay blowing warm and only go back to blowing cold when I floor the gas pedal. Then it will blow cold again.

I just picked up the truck from the shop and the guy tells me all is fine pressure readings are fine and it should be working, no leaks. I get in and can tell its been sitting with the ac running because of the big puddle of water under the truck. I get in start it up and it blowing warm again. The shop was closing for the day so I didnt even bother with the shop, I just left. They didnt charge any money for this visit. I get on the main road and floor the gas pedal and it starts blowing cold again.

What to do? If some one could tell me what gauges to buy and if I can maybe fix this myself it would be great. I have spent at least 1500 dollars on this ac system with conversion and all and still at square one it seems. I lost count of how many compressors, accumulators, and switches replaced.

Dougflas on Sat May 23, 2015 5:02 PM User is offline

First, you can rent guages from Autozone. When the truck is idling with the AC turnrd on, see if the clutch on the compressor is engaged. The center hub should be turning. Does this vehicle have a wide open throttle switch on the accelerator? It may not be working properly thus removing 12 volts from the clutch. Also, check the cooling fan. You may not be getting enough airflow at idle speed due to a non-efficient cooling fan set up. Tell us what the high side guage reads whie at idle. Then mist the condenser with a water hose and note the pressure. If the high side drops like a rock, you have an airflow problem with the condenser.

BigTruckDriver on Sat May 23, 2015 7:22 PM User is offline

Quote
Originally posted by: Dougflas
First, you can rent guages from Autozone. When the truck is idling with the AC turnrd on, see if the clutch on the compressor is engaged. The center hub should be turning. Does this vehicle have a wide open throttle switch on the accelerator? It may not be working properly thus removing 12 volts from the clutch. Also, check the cooling fan. You may not be getting enough airflow at idle speed due to a non-efficient cooling fan set up. Tell us what the high side guage reads whie at idle. Then mist the condenser with a water hose and note the pressure. If the high side drops like a rock, you have an airflow problem with the condenser.I will try that. Thanks for the helpful tips on trying to find my issue. I will work on this in the next days and report what I find.

TRB on Sat May 23, 2015 8:42 PM User is offlineView users profile

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BigTruckDriver on Tue May 26, 2015 8:26 PM User is offline

Quote
Originally posted by: Dougflas
First, you can rent guages from Autozone. When the truck is idling with the AC turnrd on, see if the clutch on the compressor is engaged. The center hub should be turning. Does this vehicle have a wide open throttle switch on the accelerator? It may not be working properly thus removing 12 volts from the clutch. Also, check the cooling fan. You may not be getting enough airflow at idle speed due to a non-efficient cooling fan set up. Tell us what the high side guage reads whie at idle. Then mist the condenser with a water hose and note the pressure. If the high side drops like a rock, you have an airflow problem with the condenser.
I will be receiving the gauges in the later part of the week. I know its really next to impossible to diagnose with out gauges but I still have some questions Ill ask to see if I can get a head start. This vehicle does not have a wide open throttle switch.
I tightened up the belt and increased idle speed to see if that would help . It did not. Now it seems to be blowing warm driving at highway speed also not just sitting in traffic. I did notice that now when the air is blowing warm the compressor is not turning. I turned the switch on the ac off then back on and the ac compressor did turn back on. After about another half hour of driving the ac started to blow warm again I got out and checked the compressor and it was not turning. I turned the switch off and on but this time it did not turn the compressor on. I revved the engine up and the compressor turned back on blowing cold.

mk378 on Tue May 26, 2015 9:29 PM User is offline

I think the compressor is right on top of the engine so you can relatively safely hit the clutch plate with a wooden stick. Do this while the truck is running, A/C switch on, but compressor not engaged and blowing warm air. If tapping the plate makes the compressor pull in right away, the clutch gap is too wide which is an easy fix-- but you will need a special GM clutch plate installer tool. This tool should be available at local parts stores. (although the one commonly found has metric threads for the compressor shaft, your compressor if original may be old enough to have inch threads and you need a different tool.)

Revving the engine makes everything vibrate which is similar to tapping on the plate-- you don't have to hit it hard just help the magnet a little and it will snap down and run cold until the next cycle when again it fails to engage.

If it doesn't seem to be the clutch, the pressure switch on the accumulator also can become intermittent-- tap on it-- realize the base is only plastic though. Also check for loose wires especially on the 2 wire plug for the clutch coil.

Edited: Tue May 26, 2015 at 9:42 PM by mk378

BigTruckDriver on Wed May 27, 2015 9:58 PM User is offline

Quote
Originally posted by: mk378
I think the compressor is right on top of the engine so you can relatively safely hit the clutch plate with a wooden stick. Do this while the truck is running, A/C switch on, but compressor not engaged and blowing warm air. If tapping the plate makes the compressor pull in right away, the clutch gap is too wide which is an easy fix-- but you will need a special GM clutch plate installer tool. This tool should be available at local parts stores. (although the one commonly found has metric threads for the compressor shaft, your compressor if original may be old enough to have inch threads and you need a different tool.)



Revving the engine makes everything vibrate which is similar to tapping on the plate-- you don't have to hit it hard just help the magnet a little and it will snap down and run cold until the next cycle when again it fails to engage.



If it doesn't seem to be the clutch, the pressure switch on the accumulator also can become intermittent-- tap on it-- realize the base is only plastic though. Also check for loose wires especially on the 2 wire plug for the clutch coil.Ok, I did just what you said and it did engage the clutch as soon as I tapped it and blew cold, BUT,,,,,,,, while looking a little closer at the face of the clutch It looked as if it had very faint oil spots around the face and front edge of the pulley. Is this a "normal" area that it would leak from? I thought a leak would likely be at the back side of the pulley , around the shaft. That area didn't look oily. I found a old black light from the kids and did not see any of the spots glowing from the dye where the oil spots were. The very light spots that I did see after looking real close could be wd40. I did spray the area down a few months ago. I didnt spray directly into compressor pulley but its the only thing I can think of, if its not refrigerant dye.

Every part is new for the r134 except for the cooler that goes inside the cab. I did take the box apart and clean the coils with high pressure water. Everything else has been replaced. I would say that the compressor is about 1 1/2 years old.

I almost forgot, thank you and the others for the help in trying to figure this out.


Edited: Wed May 27, 2015 at 10:10 PM by BigTruckDriver

BigTruckDriver on Thu June 04, 2015 11:05 PM User is offline

Thanks for the help I adjusted the clutch from .020 to .014 and all seems fine now .

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