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Old 07-10-2010
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Air conditioning - strange problem

Hello, my air conditioner has been blowing out hot air and is having some dificult to interpret symptoms. It has been an intermittent problem and untill lately I've not been able to catch the problem to troubleshoot it. With the engine at idle, I will turn on the A/C on and the engine will slightly rev every few seconds. The A/C clutch usually does not engage. I have checked the refrigerant pressure and it read in the normal range. I have also checked for voltage after the refrigerant pressure cut off switches and voltage is passing through them.


Every time the engine revs i can feel the Wide open throttle cut off relay click. I unplugged the relay and the engine quit revving. There is a wire right before the WOT relay that goes to the pcm, I assume that this is where the pcm senses that the A/C is turned on.


Now here is the strange part.....
With the WOT relay in place, i disconnected the wires to the A/C clutch and tested for voltage. I got a reading of about 14 volts. Disconnecting the clutch wires also caused the revving to stop. But the instant i reconnected the clutch wires the engine started revving every few seconds and the WOT relay started clicking again. The clutch will occasionally engage but only for an instant. I think that voltage is being pulsed to the clutch when the WOT relay clicks. With the clutch wires in place I checked the voltage again and read zero. I'm pretty sure that the relay is intermittently cutting off voltage to the clutch.

I cant figure out why the pcm would intermittently cycle on and off the WOT cut off relay. And why would the A/C clutch wires being disconnected would make any differance in the engine revving repeatedly. Is there anything other than the Throttle position sensor that would tell the pcm to activate the WOT cutoff relay? I miss my Air conditioning. Do you guys have any thoughts?????

Thanks
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Old 07-10-2010
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sounds like theres a wiring problem somewhere in that circut to the ac compresser
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Old 07-19-2010
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check and make sure you dont have a bad high and/or low cut off switches
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Old 07-20-2010
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Replaced the low pressure switch and now the AC works!!!!! The switch was reading a few ohms of resistance. It was enough to keep the compressor coil from engaging. Also, the computer senses the voltage to know when the ac is on. The added resistance of the pressure switch caused the engine to repeatedly rev as the WOT relay cycled. Initially, i had overlooked the switch as the problem since it had a very low resistance. I thought i probably wasn't making good contact with my multimeter. If you are troubleshooting a relatively low voltage circuit (12V) a small resistance can make a big difference in the amperage that the circuit will draw.
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Old 04-18-2011
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air conditioner max position

my 2002 ranger max ac position is not working right. 3.0
when in max position and engine under load it stops blowing air out of vent until the acceleration is stopped.......... then it starts blowing but does not seem to blow as hard as it use to in the max position... any ideas??::
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