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anybody have ac troubleshooting checklist?
- Thread starter CLOISER
- Start date
thebrick
NAXJA Forum User
- Location
- Chattanooga Area
http://www.askamechanic.info/askamech2/content/view/73/47/
Not sure if this will help, but it is a good read...
Not sure if this will help, but it is a good read...
- Location
- Southern Maryland
needs a wiki for this kind of stuff....Anyways, first step is check if the A/C compressor clutch is engaging when the A/C is turned on (listen for a loud "click" when somebody inside turns it on). If it isn't engaging then start looking at possible causes.
Most likely is that the system is low on refrigerant, and the low pressure switch is not closing, which is in turn preventing the compressor clutch from being engaged. You can check this by manually jumping the wires on the switch pigtail momentarily (put a small 2" piece of wire on the pigtail) and listening for the compressor clutch. If the clutch engages, you need to charge the refrigerant (better yet, take it somewhere and have them find the leak beforehand).
If the clutch still doesn't engage, the next most likely problem is that the clutch has too large of an air gap for the clutch magnet to work properly (parts get sloppy as they get old). Try lightly pressing against the clutch face with a piece of wood to see if the clutch jumps closed. If so you need to adjust the air gap by removing shims.
If lightly pressing against the clutch didn't make any difference, you have a control problem somewhere. You'll need to trace the control wire for a signal and see if it's damaged anywhere.
- Location
- Rainy side of Washington
To start out - like ehall said, probably due to lack of refrigerant.
Use a DMM to measure the low and high side pressure switches. If either is open, the compressor will not even try to turn on. If the low side is open, you don't have enough refrigerant (leaky system etc) or it's a defective switch. If the high side is open, it's a defective switch most likely since the compressor hasn't run for while.
Use the DMM to measure the resistance of the clutch signal wire to ground - should definitely be under about 10-20 ohms but I'm not sure what the spec calls for. If it's over that, the clutch is certainly bad.
Try jumping the clutch wire directly to the positive battery terminal momentarily. If the compressor kicks in, you have an electrical problem of some sort - since you already verified the two pressure switches, it's something in the wiring harness, ECU, AC clutch relay, dash controls, etc.
Use a DMM to measure the low and high side pressure switches. If either is open, the compressor will not even try to turn on. If the low side is open, you don't have enough refrigerant (leaky system etc) or it's a defective switch. If the high side is open, it's a defective switch most likely since the compressor hasn't run for while.
Use the DMM to measure the resistance of the clutch signal wire to ground - should definitely be under about 10-20 ohms but I'm not sure what the spec calls for. If it's over that, the clutch is certainly bad.
Try jumping the clutch wire directly to the positive battery terminal momentarily. If the compressor kicks in, you have an electrical problem of some sort - since you already verified the two pressure switches, it's something in the wiring harness, ECU, AC clutch relay, dash controls, etc.
