Engine Size: 2.4 L
Refrigerant Type: R134a
Ambient Temp: 90's
Country of Origin: United States
I'm just looking to get some ideas on what the possible problems could be with my A/C. Here's the basic problem my A/C it will blow cold air from anywhere between 10 minutes to over 45 minutes and I mean super cold I put a temp. probe in one of the vents and it read 52 degrees. I'll be driving along and then all of the sudden I smell kind of a stagnant odor from the vents and then it stops blowing cold air. I have noticed that on days with less humidity that the cold air will run longer but after 45 minutes it still stops blowing cold air. My father is a retired mechanic and says it sounds like it's a bad expansion valve and since he broke his back and no longer has any of his tools, he can't really help me with it. I've already taken it to one A/C place and they did an evacuation and refill but the problem still happens. I just don't want to get ripped off and would like to have some knowledge on what could be wrong before I take it in.
It sounds like it's icing up, like frost in a refrigerator. That blocks the airflow. There is a thermostat to keep the evaporator from getting too cold, which may be malfunctioning.
You can also try controlling it manually. When it first starts to do it, release the A/C button and let it thaw out (fan still on). Then push the button again and see if the cold air returns.
I've tried that too, no dice. After it quits blowing cold air it won't work again until 5 or 6 hours later.
Another common problem is the compressor clutch won't engage after it gets hot under the hood, because the gap is too wide. To test this, wait till it stops cooling, park the truck and keep the engine running and the A/C button pressed. Look under the hood to see if the compressor is engaged (If it is, the clutch is not the problem). If not, try using a wooden stick or something to tap the clutch plate on the front of the compressor and see if it snaps in. Be extremely careful not to get into the fan, belts, and other moving parts.
It could be that you have a bad evaporator temperature switch. I'm not exactly sure what the setup is on these trucks, but I suspect it has one. The switch is probably opening up to prevent the evaporator from freezing, then not closing again to turn the compressor back on in a reasonable length of time.
Should you find the clutch is not engaged and hitting the plate doesn't help, next see if the compressor clutch is getting powered from the wire from the truck. If not it is a bad switch or other electrical problem.
On the way home it quit cooling like always, I pulled over and the clutch is engaging, so I don't think that's the problem. It cooled for over an hour I had to stop for gas and it quit cooling 5 minutes after I got going again.
Since the clutch stays engaged you need to measure the pressures to diagnose further, but I would be inclined to agree with the expansion valve at this point. Valve could also be freesing internally due to water contamination in the system.
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