damned a/c

[jblueridge]

My air con will not come on in my BJ74.
I "jumped" the compressor and it works. The Freon shows bubbles in the sight glass for a while then calms down.
I used a multi-meter on the refrigerant pressure switch: it shows no resistance so the switch is working and there is enough Freon in the system.
The thermistor I am not so sure about. It's power input lead showed about 4V: can that be right?

I used the FSM wiring diagram to try to figure out the a/c amplifier. I measured 24V on pins 1&2 but
pin 8, which has a heavy gauge wire on it, had no voltage or continuity to ground.

I opened the amp's case and everything looks real clean.

Anyone have a pin out chart, or know what the meter should be showing for the a/c amp leads?

 

[jblueridge]

I've checked many of the items in the FSM checklist.
I can't find the Temp. Control Resistor.
I assume refrigerant is not empty as I can see it in the sight glass.
The thermistor is inside the evaporator's housing: I don't want to take the evap. out. I bypassed the thermistor and there was no change.
I don't know how to check the electrical connections of the A/C Amp.
I have not found any noticeable electrical faults.

Any help would be appreciated.

 

[ozcrusier]

When the air conditioning gets low on gas the system will shut down automaticity. When the system gets recharged with gas it will work again.

 

[jblueridge]

Yes, but pressure switch shows that there is enough gas.
Also, when I "jump started" the compressor the flow through the sight glass appeared nominal.
Not sure where the problem is still.

 

[Cavalier2000]

When you jump the compressor does the air get cold at all?

 

[jblueridge]

Yes, frost forms on some of the engine bay piping.

 

[Eggpattern]

You're narrowing it down. Seems to be either the receiver or expansion valve. I've replaced both a couple of times.

 

[jblueridge]

Hmmm. The whole system was re-done last year by a pro. Actually, 11 months ago.
I will not be happy if it is something he did or did not do.

I am taking the cruiser back to that guy so at least maybe I can get a deal on the fix.