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  #16  
Old 06-12-2015, 11:20 PM
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He connected gauges and showed me high side about ~150 or less. As for the evaporator.....I do get cold air in the beginning, but then it warms up and won't get cold again unless car sits off for a while.
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  #17  
Old 06-13-2015, 10:28 AM
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Originally Posted by 97 SL320 View Post
From your post 10, you are seeing 200 PSI on the high while running, this is evidence that the compressor is working. Are you still getting 0 PSI on the low side while running?

Is so, the expansion valve is stuck shut and not allowing freon to enter the evap coil.

Some compressors ( my 97 C280 ) are variable displacement and volume is regulated by looking at low / high side pressure. ( maybe just one pressure I don't recall the details )
Variable displacement compressors cannot be fully tested by pressures although you can get pretty close. To be completely to spec it has to be fully evacuated and recharged by weight.

Before replacing the compressor I'd replace the expansion valve.

Btw if you do in fact need a compressor I have a brand new Denso 10pa15c in box I'll sell to you less than anywhere online...it's been sitting in my garage after I thought mine was bad and I need it gone now.

Do yourself a favor and go to harbor freight and buy the ac gauge kit it's 50 bucks then you can do all this yourself. 150psi is too low to cool. You'll need closer to 200 before you will feel anything.
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  #18  
Old 06-14-2015, 12:04 PM
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Originally Posted by ps2cho View Post
Variable displacement compressors cannot be fully tested by pressures although you can get pretty close. To be completely to spec it has to be fully evacuated and recharged by weight.

Before replacing the compressor I'd replace the expansion valve.

Btw if you do in fact need a compressor I have a brand new Denso 10pa15c in box I'll sell to you less than anywhere online...it's been sitting in my garage after I thought mine was bad and I need it gone now.

Do yourself a favor and go to harbor freight and buy the ac gauge kit it's 50 bucks then you can do all this yourself. 150psi is too low to cool. You'll need closer to 200 before you will feel anything.
I do have the gauge set up. And he's right, it's now at <200 hi side. I was reading that the compressor can be rebuilt by changing out the seals and it takes maybe 45 minutes. Anyone know anything about that?
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  #19  
Old 06-14-2015, 12:38 PM
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Are you still getting 0 PSI on the low side and 150 on the high? As long as you have enough freon in the system, this shows that the compressor is pumping and the expansion valve is stuck shut. Even with a low charge you will get spurts of cold air.

From your description you get initial cooling that goes away after a while. If the compressor was bad, the pressures would fall off as the cooling level drops.

A 45 min rebuild is not likely outside of a production environment where dozens are being built at the same time.
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  #20  
Old 06-14-2015, 01:56 PM
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Freon is fully charged. I charged it, he charged it and still yielded the same results.
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  #21  
Old 06-14-2015, 02:26 PM
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You still haven't given both high and low readings -- the reason for my post that you need gauges. High and low work in tandem together...
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  #22  
Old 06-14-2015, 04:50 PM
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High is less than 150 low is zero
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  #23  
Old 06-14-2015, 05:16 PM
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Do you understand my post 19 and why the pressures you have point to a stuck closed expansion valve?
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  #24  
Old 06-14-2015, 10:30 PM
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Would an expansion valve that is stuck closed still allow for brief cooling? During the first 30 - 45 seconds of start up?
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  #25  
Old 06-15-2015, 02:05 AM
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Low at zero means there is a restriction in the system. Figure out where it is. The line that goes from compressor to condenser to drier to expansion valve should be Hot. If it's cold anywhere on the hoses you have found the problem. If it's all hot -- replace expansion valve.

To your question yes its not plugged enough to allow nothing yo happen...it's just when the compressor starts pulling it creates a vacuum.
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  #26  
Old 06-15-2015, 11:49 AM
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If it was mine, I would just go ahead and replace the drier/receiver and expansion valve, pull a vacuum and recharge. Then decide if the compressor is bad.
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  #27  
Old 06-15-2015, 04:43 PM
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Well as I've stated before the forum has never steered me wrong and plus replacing these parts would need replacing anyways. I will go ahead and do this then report my findings.
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  #28  
Old 06-15-2015, 05:59 PM
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Sounds like a clogged expansion valve. Once you pull the exp. valve, inspect it for debris. If it has debris, then you might need a new compressor along with a system flush. If not, you are ok, just replace the valve, pull a vacuum and charge.

When replacing o-rings, recommend using Nylog (blue for R134 and red for R12) to lubricate the o-rings.
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  #29  
Old 06-15-2015, 07:11 PM
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Originally Posted by lsmalley View Post
Would an expansion valve that is stuck closed still allow for brief cooling? During the first 30 - 45 seconds of start up?

Yes, my 97 SL320 was like that. The valve is open when things are sitting, it starts to close as the evap gets cold / pressure rises then is supposed to open when more cooling is needed. It is sticking shut not letting freon into the evap and stays stuck untill pressures slowly equalize with the AC off. There isn't anything to clean, a good brand like 4 Seasons is ~ $ 30 .

For most modern cars, there is a single nut holding the hoses on, then 2 allens holding the valve to the evap. There will be 4 different sized o rings that need a bit of compressor lube during install thought a bit of oil would be OK. If the nuts / allens are excessively tight, hold the block from twisting to keep pressure off the evap tubes.

When the expansion valve sticks / does not open, all the freon ends up between the compressor outlet and expansion valve. This is evident by the 0 PSI on the suction / low side and decent pressure on the discharge / high side.
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  #30  
Old 06-18-2015, 07:52 PM
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Anyone know the size hex key I need to remove the expansion valve? It's somewhere between a 3mm and 4mm
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