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Help diagnosing readings on a motor swapped car?

apcrews on Tue July 27, 2010 11:46 AM User is offlineView users profile

Year: 1999
Make: Cheverolet
Model: Camaro
Engine Size: 5.7L V8
Refrigerant Type: R134
Ambient Temp: 84
Pressure Low: 100
Pressure High: 35
Country of Origin: United States

Hi, I'm trying to get the A/C working in a project car of mine. It's a 1993 Mazda RX7 with a 1999 Cheverolet Camaro LS1 V8 in it.

These are the parts in the car right now:

99 Camaro Z28 A/C Compressor
Custom line from compressor to 1990 Camaro Receiver/dryer
Custom line from dryer to generic evaporator
Custom line from evaporator to Mazda RX7 hardline
Generic pressure switch plumbed into the RX7 hardline
Mazda RX7 evaporator
Mazda hardline back to the compressor

The previous owner said he had an "A/C shop" make this system and it worked fine for about 4-6 months before he'd have to recharge it - enough to get through the summers with it.

The system has been empty (but closed) for the last 2 years. I went to recharge it yesterday and got wierd readings. First I recovered what was in the system, then pulled vacuum for 30 minutes, then charged with 1.35lbs (to start). During the charge process the high side pressures never moved, and the low side shot up to 100psi.

After the charge was finished, the low side never settled. It stayed at 100psi and the high side got up to 30-40psi. With the engine running the compressor clutch doesn't engage when I hit the button... I haven't tested to see if it's the clutch, or just the high lo-side pressure making the safety switch not let the clutch engage.

The pressures should equalize after charging with the motor off, right?

What does this mean? Definitely a bad compressor?


1stbscout on Wed July 28, 2010 9:57 AM User is offlineView users profile

It is possible the high side has not opened the shrader valve so the gauge is not reading the actual high side pressure on the system.

Before worrying about the compressor..... find the problem that is causing it not to engage. Could be a bad clutch or any of the electrical connections. Check for power at the clutch before doing anything else. Track it backwards through any and all switches (low side cycling switch, high side cut out etc.) until you find the electrical problem.

In a none running state the compressor will not keep the high side low.

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