AC Problem/Question

[Silverbullet]

Ok, so the air blows cold, I drive for 20-30 minutes... it gets to not be cold... The fan is still blowing...I checked and the Compressor Clutch is not turning... It has a full charge of 134a. The engine runs great, and was not hot. What should I look at?

Thanks,
Craig

[Bitsyncmaster]

You need to get gauges on it. It could be a lot of things causing the problem. Low and high side pressure readings will show us what is wrong.

[Ron]

Did you evacuate it before you charged it? If you didn't, it could easily be it had a small leak...icing up now from moisture in the system.
We can guess forever, but we need data and, like Dave said, you need a set of gauges to give it to us...:)

[David T]

One of 2 things. You may no longer have a "full charge" of -134 or there is moisture in the system freezing up. If you don't have a set of gauges get a tire gauge and check the low side when it isn't running. If it isn't close to 60 psi you don't have a "full charge". This quick test won't work with a tire gauge if they changed the service valves to -134 style.
David Teitelbaum

[Silverbullet]

It has the 134 fittings... with the engine off the low side is about 75 psi... running it is about 38 psi.

[Ron]

It has the 134 fittings... with the engine off the low side is about 75 psi... running it is about 38 psi.
If you let it sit and cool to ambient temperature when you took the measurements, then all you can tell from this is that it was very close to 73F outside, and that your system wasn't near empty, which is all you can know if you didn't. It could have 1/3, 1/2, 3/4, or full (or overcharged, if you didn't know it was correct when you started). And that is assuming you evacuated it, which you didn't answer??

Refer to these charts:
http://dmctalk.org/showthread.php?1244-Refrigerant-Temp-Pressure-Chart
R12 characteristics are very close to 134a at the temps you are having there.

http://dmctalk.org/attachment.php?attachmentid=3771&d=1313473293
Note you should check pressures when your clutch cycles out...If you were, 38 psi is too high (should be 25-32psi).
Assuming your high side is OK, at 75F it should be ~135-170psi.
Rule of thumb- Above ~70F ambient 134a will give lower pressures than R12 (insignificant) -- above ~70F, 134a gives higher (especially approaching 100F, significant above).
If OK here, clutch coil failing when warm, evaporator icing, condenser not cooling, flaps not working and fighting heater...vacuum either/both, etc....again, ya need that high side data bud...

[David T]

It could be the low pressure switch needs to be adjusted. At this point you really need to have a set of gauges on the high and low sides and see what is going on while it's running.
David Teitelbaum

[Silverbullet]

So I have a set of gauges, but it was for R12, so I just ordered the adaptors for 134a. I will test when I get them. I did not charge the car...I bought it that way, converted to 134a. Also, when it works (short trips) when I park the car I get a water puddle. Long trips, when it quits, it does not puddle water...fyi

My guess is something is killing the power the the clutch...the inside fans stay on, and the fans on condenser are working.

Craig

[chris williams]

Apologies for this question, however looking at the back of the compressor which is the high pressure side and which is the low??
Thanks

Chris

[Bitsyncmaster]

Apologies for this question, however looking at the back of the compressor which is the high pressure side and which is the low??
Thanks

Chris

R134 ports will only fit one way. But on my car the high pressure has a red cap and the low has a blue one.

[DMCMW Dave]

R134 ports will only fit one way. But on my car the high pressure has a red cap and the low has a blue one.

Yeah but he wants to put the adapters on the R12 fittings which are the same size. Standing behind the car and facing the front of the car, the low pressure is on the left side. I.E. the driver side of the compressor.

[Bitsyncmaster]

Yeah but he wants to put the adapters on the R12 fittings which are the same size. Standing behind the car and facing the front of the car, the low pressure is on the left side. I.E. the driver side of the compressor.

That's how they should be. Also the low pressure hose is a larger dia. than the high pressure hose.