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Odd problem -- Bad compressor?

Fishermark on Mon June 08, 2009 6:30 PM User is offlineView users profile

Year: 1991
Make: Chevy
Model: G20- Sportvan
Engine Size: 5.7
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 50
Pressure High: 65
Country of Origin: United States

I just changed out most of the items in my vehicle. It is a 1991 Chevy G20 full sized van with a 5.7 liter engine and dual ac. I installed a new parallel flow condenser, all new hoses - even the long runs to the back, new expansion valve at the back and new orifice tube at the front. New accumulator. Physically removed front and rear evaporators and flushed thoroughly.

The chart calls for 11 ozs of oil and 72 ozs of refrigerant. I put 6 ozs of DEC PAG 150 in the compressor and manually turned it several times. I put the remainder of the oil in the accumulator.

After an hour vacuum, I proceeded to charge the system. I got about three cans in the system when all of a sudden a loud pop and hissing came from the back of the compressor. I can only assume that there is a safety valve in the back of the compressor?? Here is a picture I took -- there used to be a little square yellow sticker on the back - which is now been blown off and is stuck on the bottom...





This is a brand new compressor, not rebuilt. I must say that when I tried manually turning the compressor when I added the oil I could not budge it. I had to power up the clutch and then I could barely turn the compressor. I reasoned it was just tight and would probably loosen.

Is my compressor bad?

When I was charging, the high side of the gauges never moved much. It never got above 65 or so. Right now the static pressures are over a hundred on the low side and around 60 on the high. With the engine running and ac on, the pressures are both around 60.

The compressor gets very hot within a minute of running.

Here's what the pressure does when I turn off the engine:

chris142 on Mon June 08, 2009 9:52 PM User is offline

That is a high pressure pop off valve. For whatever reason you had too much pressure. Fan clutch? Overcharged? Blocked Orifice etc. They don't pop off til over 500 psi.

GM Tech on Mon June 08, 2009 11:56 PM User is offline

Compressor is great! Heck it is capable of pumping 525 psi (pop off valves are rated at 525-575 psi and are self resetable....you have a major high side blockage - or absolutely no air flow acroos condenser-- and evidently no high pressure cut-out switch- or the blockage is in front of that switch- as is your high side gage port.....you can't see the high pressure if it isn't at the high side port.

There is a small chance the pop off valve is defective- set tool low-like at 200 psi or so-- you could always swap it out with the one off your old pump if you want to test for it....they have an o-ring on the seat-so it is no big deal to swap.

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Fishermark on Tue June 09, 2009 9:19 AM User is offlineView users profile

Okay, so it sounds like there is a blockage.... help me out with an educated guess as to where to start looking. Everything is new. I took pictures to show what I have - what do I do from here???

I didn't blow through the new hose assembly with the muffler - nor did I do anything to the new parallel flow condenser. I simply took the plastic caps off, lubed the fittings and o-rings with nylog blue and assembled everything.



















GM Tech on Tue June 09, 2009 10:51 AM User is offline

You may not have a blockage- you may have poor airflow across condenser- is clutch fan good-- roaring with high velocity-- most clutch fans wait on heat to activate- your condenser needs air right now- while engine temp is still cool-- try this-- mist the condenser with a garden hose while charging- see if that helps-- although you should have seen high pressure in your gage set-- but do you know the gage set is depressing those conversion fittings properly? does gage respond when you attach it- jump up to static pressure as you turn the valve?

I have seen punch-out blockage in the mufflers before- maybe 3 times in my 20 yrs-- where the little aluminum chip they poke out to make the muffler is trapped inside it, and it blocks the refrigerant flow- causing pop off valves to blow-- They rattle if such is the case- but you have to have the hose off and shake it.

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Fishermark on Tue June 09, 2009 11:15 AM User is offlineView users profile

I don't believe it is an airflow problem. I seem to have a good flow of air pulling through the condenser. I will double check the gauge to make sure the high pressure side is engaging the schrader valve and report my findings.

I hope I don't have to remove the hose(s) and start again!

TRB on Tue June 09, 2009 11:35 AM User is offlineView users profile

Pull a OT and post an image of it.

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Fishermark on Thu June 11, 2009 6:31 PM User is offlineView users profile

Well, I had a little time this afternoon to take a better look. It seems the high pressure port connection at the gauge was not making full contact. I changed out the adapter and tried again... sure enough, the pressure rapidly builds up.

I started the engine and turned the AC on max cool and watched the pressure gauge - it just kept going up. In less than a minute it was up over 300 lbs. The compressor was incredibly hot to the touch as was the condenser.


Quote
Originally posted by: TRB
Pull a OT and post an image of it.


TRB - Are you referring to the orifice tube? I have no way of capturing the 134a. If I take it to a local shop and have them evacuate it I can do that. But does the high pressure give a clue as to what is going on?

Chick on Thu June 11, 2009 6:39 PM User is offlineView users profile

What was the original failure? did you check the O tube at that time, and what did it look like. You may still have a clogged O tube.. Only way pressure can go that high is air in the system, overcharge or it's pumping against something, like a clogged O tube..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Fishermark on Fri June 12, 2009 2:34 PM User is offlineView users profile

The original failure was simply that this is a "new to me" van which has sit unused for five years. There was no refrigerant in the system at all, but the o tube I removed from the evaporator had little, if any debris. I will go ahead and remove it as soon as I get the opportunity and post the results.

Thanks.

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