AC compressor needs new pop off valve?

[HawkeyeScott]

2000 Durango. Gauges show high and low pressures in AC system are low. Compressor cycles every 6 seconds. So it's likely low on freon. BUT...when I try to add more, I get the loud PFFFT! sound of the popoff valve going off. AC guy tells me pop off shouldn't go off until 500 psi. System is under 200 on high side, so it seems like it shouldn't be popping off.

So, can you just replace a pop off valve, or do I have to buy a while new compressor? Called dealership and several parts stores say they don't carry valves. Wonder if anyone has found a workaround on something like this.

Would love any ideas. Thanks a lot.

 

[zzyzzx]

What engine and exactl model of Durango please?

Is this the expansion valve I see listed on parts websites???

 

[HawkeyeScott]

4.7. What sites? That would be great if it's that simple. Thanks, btw.

 

[HawkeyeScott]

Seeing expansion valves online now. Stupid question, is that the same as a popoff valve?

 

[punisher]

No, it is not the same.

I think that that possibly the pressure is spiking too fast for you/your gauges to see. Normally when I run across a pop off valve opening, I think clogged expansion valve or orifice tube first. There is just not a lot to a popoff valve. It either works/doesn't work, or it leaks. Never have seen one that releases at too low a pressure (but there are firsts for everything I suppose)

Honestly, a junkyard popoff will suffice if you cannot find a new one. My question is why the system doesn't shut down when the high pressure cutout switch activates?

 

[AandPDan]

An expansion valve is not the relief valve. Your truck uses whats called an orifice tube for expansion anyways.

The relief valve, according to the 2000 factory service manual is only serviced as part of the compressor assembly.

 

[Chris142]

Every time I do an ac job I keep the old pop off valve from the old compressor. They are nearly impossible to find. There are several types of threads on them depending on manufacturer. Btw they are a 1 time use because they often don't seal after poping off

 

[HawkeyeScott]

Thanks a lot guys. Sounds like starting with a $15 expansion valve might be a decent idea just in case that's causing the relief valve to blow.

As for finding a used compressor, I'm wondering how many are sitting in salvage yards out here. I'm in Idaho and there are a ton of Durangos around. Time to make some calls.

 

[Chris142]

Excessive pressures is usually caused by not enough air flow through the condenser. Not a bad expansion valve or block. Your truck should have 2 radiator fans. Ones electric and the other is mechanical. Btw you do not have an orifice tibe in this truck like someone mentioned. You have an expansion block.

 

[zzyzzx]

Can somebody post a picture of a "pop off valve"?? I suspect that I have never seen one.

 

[Chris142]

Originally Posted By: zzyzzx
Can somebody post a picture of a "pop off valve"?? I suspect that I have never seen one.


http://www.ebay.com/itm/NEW-GM-A-C-PRESS...r#ht_2276wt_881

 

[zzyzzx]

Thanks! So that is supposed to be bolted into the compressor in the OP's case?