QuestionQUESTION: A/C compressor quit working. The fuses are good. I disconnected the low pressure switch and ran a jumper between the two terminals in the wiring harness, compressor did not come on, but I ran a ground to one of the terminals in the harness and the compressor would work. As long as the ground is connected, the compressor will run, even when th A/C is turned off. I swapped out the A/C relay and nothing happened.
Strange thing is, I had replaced a bad coil the day before, all I disconnected then was the battery, the spark plug wires and the electrical plug, nothing else.
Thanks for any ideas!
ANSWER: Hi Don,
I have the '97 and '01 Neon manuals, and they differ as to the AC/heater wiring. Can you tell me the amps of fuse 7 and fuse 8 in you fuse box under the dash? That way I will know which applies. Also, which wire color at the harness to what device, when grounded, caused the compressor to work?
Then perhaps I can understand what you are tellimg me and give you a suggestion.
Roland
---------- FOLLOW-UP ----------
QUESTION: #7 fuse is 25 amp, #8 fuse is 10 amp. The blue wire with white stripe going into the low pressure switch is the one I can ground and the compressor starts working.
AnswerHi Don,
Then your wiring is similar to that of the '97 model. Did you check fuse 8, electrically? There is a component called "A/C cycling switch" whose location is listed as "center of HVAC housing", and it has three wires that run to it: a white wire from fuse 8, dark blue/orange from the A/C low pressure switch-A/C high pressure switch-powertrain control module circuit which is the circuit that the pcm senses to tell it to energized the clutch on the compressor, and finally a dark blue/yellow from the mode switch of the A/C heater control unit which applies a variable resistance to ground depending upon the position of the mode switch.
I am not sure exactly what the output signal is from the A/C cycling switch that the powertain is seeking but I suspect it is a ground signal because if you ground the circuit at the dark blue/white wire that tells the pcm to energize the clutch relay.
The fact that your jumping over the A/C low pressure switch doesn't cause the clutch to energize suggests to me that the A/C cycling switch is not doing its grounding function at the dark blue/orange wire, assuming that is its function (which I would believe because you get action when you ground the dark blue/white in that circuit).
So my suggestion would be to check fuse 8 and then see if you can find the cycling switch on the housing under the dash and observe what you can on its three pins, using a voltmeter.
Then let me know what you find.
Roland
PS: Are you certain that when you jumpered the low pressure switch that the clutch didn't work (and that you had the A/C properly called for at the control panel)? It could be that you are low on refrigerant and that although you jumpered the switch you still hadn't properly requested AC compressor function.
