Ok, the air hasn't been working since last Sept.
Recharged it and it quit after a few days, so I though it might be a leak, an left it for the winter ...called a friend with a tank and gauges, and today....

A slight charge left on the high side....put some gas in, and it took a while for the compressor clutch to kick in , but then once it did no suction on the low side, and the gauges balanced at about 70 lbs.

Waited, reved it a bit....played with the controls....nothing. Seems there is some slight temp variation high to low side but nothing of any import...

Any suggestion what the %^$# might be going on???

TIA!

 

Did the clutch stay engaged the whole time? If so my first thought would be bad valves in the compressor.

Mike

 

Clutch was cycling but not normally. Stayed on for quite a while.

 

There is a very good instruction booklet written by Porsche enclosed with the Tech CDs by Alan Moorehouse which can be obtained from Roger at 928sus.

When checking out A/C there needs to be a logical approach adopted to identify the causes for the non working and the approach that need to be undertaken to rectify the problem/s.

Your problem looks like it could be in the compressor and maybe failed suction and or delivery valves.

Refrigeration Engineering can be complicated.

 

Agreed on the complicated. However, we're not trying to cool down a disaster recovery centre here....
I've never seen something like this discussed here and I'm wondering if someone with compressor knowledge could opine.
I'm ok with the basic concepts, but I really need to take an AC course. And, when it comes to compressors (AC anyway)...I've no clue.
What is and how might a suction valve fail?

 

I too am no AC guru, but I think it's safe to assume you compressor needs to be rebuilt. Maybe you could pick up a decent used one from Frank at ninepart, he's pretty close to you.

Hope you get it sorted and blowing cold.

 

When pressures equalize, while running, it is usually a sign of bad valves...the compressor is no longer able to pump. What causes this? Running a compressor with low pressure will do it. Recharging it with liquid refrigerant will do it. Washes the oil out of the compressor. Running to high a pressure will blow out the valves, but I don't think that was your problem.

Most people pop them while charging. Not supposed to turn the can upside down or sideways....Sometimes they just break.

A low refrigerant charge, causing the compressor to "short cycle", can cause it to overheat and break.

http://www.airconcars.com/html/how_it_works.html

 

Could vary from model to model, but ...

High pressure switch, low pressure switch, start by checking voltage at the clutch control wire, and operation of the clutch, then switches etc.

I would opt for a good rebuilt unit over a used one, opening the system you need to purge, vacuum, replace receiver dryer and maybe expansion valve, flaky used compressor and you get to do it again.

 

Agreed bad valves, also with a leak the refrigerant has an affinity for oil so oil will also travel with the refrigerant as it leaks out. With a lack of proper refrigerant pressure while the system is operating the oil tends to log in the condenser. Thus also causes high heat in the compressor adding to why valves can go bad besides the previously mentioned.

 

Thanks Ron. That was helpful. I think I know now where the "beginning of the end" happened anyway.

 

Thanks!

 

I know it's been replaced once before......has one of our Vendor's ID's on it....the only other markings I can see are "16958".

Can anyone identify what I've got in there in terms of manufacturer and model maybe?

 

Any compressor cycling is NOT normal - when AC is on the compressor should run continuously unless it freezes up the evaporator.

Temperature control is not ever achieved by cycling the compressor.

Alan

 

at least on our models..... Some of the newer fords and dodges cycle according to their forums its normal.

 

Your 1990 should have come from the factory with a Nippondenso 10PA20C compressor.

Mike