Low Psi A/c Switch

[stvdalton]

Need help, going to try chnaging my low pressure switch on my a/c. The a/c works fine at idle, but get driving a while and it shuts off, especially if you put it on MAX a/c, so some people have advised the control panel inside the truck or a low pressure switch. We'll the switch is a lot cheaper. But I thought it was on the condensor canister thing, but someone said that is the high pressure switch. So where is the low psi switch located and does this sound like a good place to start?

 

Thanks!

[txab]

If you have a switch on the side of the accumulator, that is the low pressure switch. You could be low on refrigerant also

[stvdalton]

I have a mechanic buddy, we pulled all freeon out and cleaned what little build-up was on o-tube and refilled to exact amount. It sometimes doesn't kick off on normal, but within a few miles on MAX A/C.

So on the little canister on the firewall that is wrapped in some like insualtion I have a part that looks like it screws or twist in, it has a clip on it where you can unplug the wires out of it. So you think this is the low psi switch or is that the high psi switch?

Advanced auto parts show that the low psi switch is on the compressor. Not so sure the guy knew even what day it was though. HA!

[txab]

If you recharged your system your low pressure hose connection should have been on or near the accumulator. That would verify for you that is the low pressure side. Did you weigh in your refrigerant charge, putting in the proper amount specified? Here's a pic of the accumulator for your '99.

 

 

[stvdalton]

Yeah we weighed the freeon. I think it was 2.2lbs. I'll look when I get home. I don't think the guy at advanced was right about the low psi switch being on the compressor.

[Draenor]

Is the compressor cycling constantly at idle?

 

What are the readings on the low/hi sides? (also the ambient temp and humidity)

[stvdalton]

The low psi side is 40psi temp about 85, the high side I believe was around 260, but what happens when it starts blowing warm/vent temp air, the compressor never shuts off, but the high side pressure goes way up, can't remember exactly. My mechanic was even sure what was causing it. But what happens is 99% it only happens when on max a/c when after about 2-3 miles of driving, it stops blowing cold air. To actually make it blow cold again, I have to turn a/c completely off, wait a few minutes, then turn it on and it's cold again. Which lead me to believe that the max a/c air is colder going across the a/c unit or however it works and freezes up. Like I said, hardly ever does it happen on reg. a/c, but it does happen. Some seem to think it may be the climate control panel. But possiblty the low psi switch.

 

At idle it never cycles off/on. When it's on, it stays on and is fine. I can actually use max when I'm just sitting at idle and it never stops blowing cold. Very wierd.

[txab]

What does the low side read when your high side "goes way up"? Actual numbers are helpful.

 

Are any of the AC Lines frosting up, especially on the high side of the system?

[stvdalton]

The low side psi goes to 75psi when the high side goes way up. The lines I don't think have ever frosted up, they just have a crap load of condensation. But I'm sure that is normal. The only other thing if not the LP, then my quacky mechanic thinks it's the control panel. Easy to change out myself, but $$$$!

[txab]

You can never get the compressor to cycle? Even with the blower on it's lowest speed?

 

 

 

Post your question here:

 

http://www.autoacforum.com/

 

You can get better AC help at that site.

[jtupper]

I just replaced the compressor, accumulator, condensor, orifice tube and rear expansion valve on my '00 Tahoe. I used ackits.com at the direction of one of the members here. I couldn't have been more pleased with the help and direction I got from the folks over there. I ended up saving myself hundreds of dollars and I didn't know squat about auto a/c.

 

Go over there and check out the a/c forum. They will point you in the right direction.

[txab]

The autoacforum.com is operated by ackits

[stvdalton]

As far as I know the compressor is working properly. I had my buddy which is mechanic check it out, and then I also for a 2nd opinion got a real mechanic shop check it out, cost me $70 for really nothing, but they said the compressor is all fine, it is for sure a control problem.