Air Conditioning Assistance Needed

[The_Red_Baron]

Having issues with my '80 Volaré air conditioning. Anybody know of any common leaks in any lines or compressor (system in general). Shadango and I made an attempt to recharge the system, but no luck. We noticed that when the clutch engaged, the pressure would fall. Is this normal? It would only engage for a second at most. On and off again the entire time I had the air running. Any ideas on cheap ways to get my system working again? Thanks

 

[Justwondering]

By no means an expert... but here is what happened when I tried resurrecting my FA this year:
1. leak at expansion valve
2. leak at front seal of compressor
3. crossthreaded the bolt into the condenser (my fault)

You must use new gaskets every single time you take off a hose. .... every time.

There is a pressure switch on the side of the expansion valve. Mine hasn't died yet, but others on the net have said when you convert your system to 134a you should upgrade that switch.

 

[Justwondering]

I also replaced the compressor on my Suburban. I had a hose connection on the compressor that wasn't tight enough after I put it in. I got the expansion valve right on it. Didn't have to mess with the condenser.

My Silverado needed a new blower motor switch as well as the in cabin air filter cleaned and it cycled correctly and blew cool air.

My Ford Dually needed a new blower motor switch as well and it blows cold air fine.

 

[Justwondering]

Have you tried putting dye in the refrigerant to see the leak?

Also, my brother had a car that the shrader valve (port access) was leaking. It is most unusual, for I believe it is usually a gasket at a hose or a seal in the compressor that leaks.

 

[Darth-Car]

It always helps on these cars when charging a system that is low on refrigerant to put a jumper wire on the low pressure switch to keep that compressor engaged. This way you have better continuous suction to draw in the refrigerant.

 

[Aspen500]

The low (suction) side will drop pressure when the compressor is on, the high side will go up.
If the compressor cycles a lot, it could be low on refrigerant, have a bad cycling switch or a restriction in the low side such as a stuck expansion valve.

Depending on the ambient air temp, with the A/C off you should have ROUGHLY 70-90 psi on both the high and low side. With the compressor engaged, the high side will be anywhere from 150-250 again depending ambient and if you are using R12 or R134a which runs at a slightly higher pressure than R12, and the low should drop to maybe 15-20psi and then disengage the clutch and rise back to around 40 psi and the clutch should come back on.

Those pressures are all a general range where they run and shouldn't be taken as exact numbers. Ambient temp, air flow through the condenser, air flow through the evaporator all have an effect on the pressure.

Also, if you are running R134a you want the charge amount to be 80-90% of the R12 capacity called for.

 

[The_Red_Baron]

No obvious leaks. But I did it in the rain. Checked a few days later, but couldn't feel anything. Pointless at that time. Out of a.c. pro. I'm curious if it would work if I got the clutch to stay on long enough. Could be electrical, but the compressor cycled when the new stuff was put in. Now it doesn't. A combination of both maybe?

 

[Justwondering]

Get a pressure gauge and check the pressure. Aspen500 knows what he's talking about.

 

[Aspen500]

You really need an A/C pressure gauge manifold set hooked up so you can see both the high and low pressure side. It's possible to have low pressure readings that are perfectly normal but if the high side is either too high or too low, the A/C won't work or won't work well.
To be sure of the actual refrigerant charge, it needs to be recovered, then vacuumed and recharged with the proper amount. Too much is as bad as too little, almost worse. Then the other things can be evaluated if the problem still exists. Also, if a system is empty and is charged without drawing it down to ideally 29+" of vacuum to remove all the air, and then the vacuum left on at least 15 minutes to boil out any moisture (water boils around 80 degrees at 29.2" vacuum), even with the correct charge amount it won't work all that well.