what should the pressure be on both the low / high side for a 85 380se
right now the low side is around 50 psi and the high is aroun 275 psi this sound a bit high ( it is r12 ) and still not cold (but is luke cool)

Did you overcharge the system? Not enough air flow thru the radiator may also be the cause. Is there a chance that you get air in the system?

David

[This message has been edited by be459 (edited 07-20-2000).]

Are these numbers with the compressor running? What is the ambient temp. Make sure the engine is at operating temp..

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

dont think i over charged it, the compressor was running while charging, i filled untill bubbles cleared sight glass and the system was evacuated before starting every thing seemed ok except the high pressures and not as cool as before

How quickly does the compressor cycle, ie cycle between off and on. Those pressures are high, especially the low side. Was it running when you checked these pressures??

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

the comp was not cycling on and off it just stayed on

If you have done verything properly, the last thing I can think of is the expansion valve - it stuck open. In the old days, I was taught to test the valve by spraying r-12 on it and the low side pressure should drop to around zero. If it does not drop, replace the valve. Now, you cannot do this anymore for both economic and environmental reasons.

Retrace your charging procedures. Is it possible that air leaks into the system without you knowing it?


David

50 PSI on the suction side is high, but that is also temp dependent. David is probably correct, ie. expansion valve. Something puzzles me though. If you had pressures that high, your compressor should be cycling. If you want to try a quick fix effort, have some of the R-12 removed and see if it doesn't improve.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

I think the high pressure cut off is higher than 275 psi, more like 325 psi.

David

True Dave, but who knows what his actual pressure is... About 275psi doesn't really cone it down for me. If his expansion valve is malfunctioning and the compressor is not cycling, he's just going to continue to build pressure, especially if the ambient is high. He does, however have a decent differential from high side to low side, so I'm betting he's got too much R-12 onboard.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

i did remove some of the r12 with some results but now have bubbles in the sight glass , i did tap the expansion valve to loosen up any clogging i'll recheck the pressures tomorrow

If the expansion valve clogs, you will see frost around the outside of the valve and the low side pressure goes very low (zero or below). Therefore, clogging valve is not your problem.

It looks like overcharging is not the cause either that narrows down to "expansion valve stuck open" or "air in the system".

Keep in mind that when the system is just full, you will still see bubbles (also, see Benzmac's post under the subject of "A/C readings") during:
(1) compressor engaging/disengaging;
(2) you are varying the engine rpm rapidly when the compressor is engaging.

You use R12 out of a brand new can (or tank), isn't it?

David