A/C abruptly stopped working. (02 Envoy)

[Raditude]

So today, I drove across town to my mom's house. The A/C worked great on the way there. When I left, a few hours later, it only blew hot air.

The compressor engaged, so I thought maybe it needed a recharge.

I bought a recharge can, and put the gauge on and the valve, and it read nearly 200psi, in the warning (mechanical problems) area.

I have an 02 Envoy, with digital climate control. The outside temp on the climate control always reads 50F, even when it's hot out. The air conditioning and heat have worked correctly regardless of that.

Does anyone have any idea what the problem could be?

 

[triz]

Is it making any noises? Mileage? It might be on its way out.

 

[The_Roadie]

The usual advice is to NEVER add refrigerant like it's a fuel tank. If it's low, there's a reason (leak) that must be troubleshot and repaired first. If it's extra low, the low pressure cutoff switch will stop the compressor from engaging to save the compressor.

You usually need a professional with gauges to diagnose it properly. Guessing can cost you more than doing it right.

The outside air temp sensor is called an "ambient sensor" and searching for that on here or Trailvoy will reveal it's only a $7 part even at the dealer and trivial to swap out.

Functionally, you need to feel the temp of the aluminum can called the receiver/dryer (also known as the accumulator) on the passenger side of the firewall in the engine compartment. If it's frosty, then your problem is in the temperature actuators behind the dash. If it's hot, then your compressor has low or no functionality, and you need to get seen by a professional.

 

[Raditude]

Is it making any noises? Mileage? It might be on its way out.

There is a clicking noise as it idles. Sounds like something in the pulleys. It has a little over 140,000 miles.

The usual advice is to NEVER add refrigerant like it's a fuel tank. If it's low, there's a reason (leak) that must be troubleshot and repaired first. If it's extra low, the low pressure cutoff switch will stop the compressor from engaging to save the compressor.

You usually need a professional with gauges to diagnose it properly. Guessing can cost you more than doing it right.

The outside air temp sensor is called an "ambient sensor" and searching for that on here or Trailvoy will reveal it's only a $7 part even at the dealer and trivial to swap out.

Functionally, you need to feel the temp of the aluminum can called the receiver/dryer (also known as the accumulator) on the passenger side of the firewall in the engine compartment. If it's frosty, then your problem is in the temperature actuators behind the dash. If it's hot, then your compressor has low or no functionality, and you need to get seen by a professional.

Oofa. Looks like the compressor is crapping out. I'll have to take it in.

 

[budwich]

I think that you will find that if the compressor is NOT turning on, then the measurement of the pressure on the low side isn't going to tell you much / anything. You need to look further, the high side pressure, the ac relay, etc.... and voltages at a few components there of including the clutch.... or as suggested, you could take it in and get it looked at by an expert...

 

[coleman]

Raditude, did you ever get this resolved?

I'm having a similar issue.

I can drive around and the air blows ice cold, then out of nowhere, you can feel the temperature start to go up. One time the air temp went up and down and up and down like the compressor was dis/engaging over and over. When the air goes out, if I let the car sit overnight, it's ice cold again in the morning.

I did bring it to a local auto AC mechanic, but unfortunately, it was while it was working. They checked all the levels, pressure, etc. and could find nothing. I was told that I need to bring it in while it's not working so they can diagnose it while the problem exists, but it's just so unpredictable that it's difficult to do that.

This just happened again today. I drove it home and checked the dryer and it was warm while the compressor was engaged. The only thing that leads to me think that my compressor is on its way out (and I've already replaced it once), is that I used to hear a loud squeak when the compressor clutch engaged. Now I don't hear that anymore, but I haven't heard that for awhile now, even when the AC working fine. I don't know . Perhaps it's the pressure switch on the dryer. I wonder if that simple fix could be the problem.

 

[coleman]

Update:

I went and picked up a pressure cycling switch. No AC on the way to the parts store, no AC on the way back. I changed the switched, started up the truck, 3 seconds later I heard the compressor kick in. Blows ice cold. Now, this would happen before, so the real test is if continues to blow cold day after day.

One thing I did notice is that I was able to unscrew the old switch by hand. It was definitely not tight. There was a little pop when I unscrewed it and a tiny amount of fluid that came out of the connection so I assume that even though it wasn't tight, it was still connected well enough. Either way, the new part stays in.

 

[coleman]

Update:

I went and picked up a pressure cycling switch. No AC on the way to the parts store, no AC on the way back. I changed the switched, started up the truck, 3 seconds later I heard the compressor kick in. Blows ice cold. Now, this would happen before, so the real test is if continues to blow cold day after day.

One thing I did notice is that I was able to unscrew the old switch by hand. It was definitely not tight. There was a little pop when I unscrewed it and a tiny amount of fluid that came out of the connection so I assume that even though it wasn't tight, it was still connected well enough. Either way, the new part stays in.

Update: The problem was definitely the pressure switch. I haven't lost A/C once since I changed it. Easiest fix going.

 

[meerschm]

Update:

I went and picked up a pressure cycling switch. No AC on the way to the parts store, no AC on the way back. I changed the switched, started up the truck, 3 seconds later I heard the compressor kick in. Blows ice cold. Now, this would happen before, so the real test is if continues to blow cold day after day.

One thing I did notice is that I was able to unscrew the old switch by hand. It was definitely not tight. There was a little pop when I unscrewed it and a tiny amount of fluid that came out of the connection so I assume that even though it wasn't tight, it was still connected well enough. Either way, the new part stays in.

the low pressure switch mounts to a valve very similar to the one you use to put air in your tires.