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1999 jeep wrangler a/c works in Park but not drive...go figure.

jesaire on Mon May 21, 2012 11:56 PM User is offline

Year: 1999
Make: Jeep
Model: Wrangler
Engine Size: 4
Refrigerant Type: 134
Ambient Temp: 90
Pressure Low: .?
Pressure High: .?
Country of Origin: United States

To a/c Master mechanic,
I am having a weird one happen to me ,hopefully you have experienced this one. My a/c works in Park but once you put in drive the a/c clutch disengages and shuts off, fan still blows.. Also can you tell me if the clutch is always 12 vdc?

Weird huh?

Look forward to the responses

Jesaire, CA

mk378 on Tue May 22, 2012 12:14 AM User is offline

Many cars will drop out the compressor if the idle rpm goes below spec. It is in the PCM software to help prevent the engine from stalling. If that is what is happening, pressing the gas pedal slightly will make the compressor come back on. Then you'd need to check the idle air valve to make sure the engine can get enough air to keep rpm up despite the load of the transmission and the A/C.

Edited: Tue May 22, 2012 at 12:16 AM by mk378

jesaire on Wed May 23, 2012 1:52 AM User is offline

Could you tell me if my compressor utilizes a zenor diode, I was simply creating a simple electrical circuit including my low and high pressure switches to try and rule out the under dash wiring and I may have accidently damaged my clutch coil, I do have continuity through the coil and show no indication of a grounded compressor. Shouldn't I be able to start the compressor with 12 vdc?

Much appreciated

mk378 on Wed May 23, 2012 9:28 AM User is offline

Resistance of the coil should be 3 to 4 ohms. Some clutch coils have an internal parallel diode (a regular diode, not zener), which will blow shorted if trying to jump the compressor with the wrong polarity. There aren't any with a series diode. To rule out the controls you just need to check if the compressor is getting 12 volts across the coil when it should be on.

Edited: Wed May 23, 2012 at 9:31 AM by mk378

GM Tech on Wed May 23, 2012 9:59 PM User is offline

My situation is just the opposite-- '01 Venture works in gear but not in Park - see post above - go figure-- what a day-- opposite issues day I guess!

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

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