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AC Diagnosis Confirmation

1545 Views 7 Replies 7 Participants Last post by  RonaldCarter
I'm looking for a bit of help diagnosing the AC on my 2001 4.6 HSE. The AC was not working when I purchased 2 years ago, but now it is time. I have already replaced the fuse box and all positive and earth cables to pass the electrical sticky. The old fuse box had relay 7 area burnt and was causing several other issues. Since the replacement I have kept the AC off and replaced with a new relay. The AC head unit is the correct part number with the pixel repair done so the book symbol shows. Using Nanocom for diagnosis shows two recurring faults, Right hand blend motor and Heater core temp sensor. The AC compressor is not engaging and both the high and low side pressures read the same, 84. The PO told me it just needed a re-gas but I am thinking it needs a dryer, pressure switch, and possibly a compressor. I intend to change all the O-Rings while I have the system apart. Does this seem to be on the right track?

I intend to pull the dash next week to repair the dash pad and right hand blend motor. I also plan to re-seal the duct work as all the original foam has perished resulting in most of the soon to be cold air being lost under the dash. I was intending to use a foam weather strip sourced from a local hardware store but am concerned about it holding up in the high heat. Does anyone have any experience with this?
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I sealed my ducts with Good Quality 3m duct tape. The cheap stuff will fall off.
The blend motor wont affect your ac but the temp sensor may. It is right on the heater core tube behind the glove. The high and low will read the same until the compressor kicks on. I also used some foam but mostly connected everything with the tape. My pressure is great. It was only good before. You could try a regas but if you think the orings are bad it will leak out anyway. Check your Nano for Hvac setting values that AC GRANT= YES . Then you know it is trying to run.
Good Luck
I would check a few other things before pulling the system apart and necessitating a re-gasing as your pressure sounds OK to me. You need to check for proper operation of the trinary and binary switches. Also check the connections in the passenger's side kick panel. there is a large white plug in there with some wiring for the AC system. If that is corroded it will not work. There was a post a little while ago that had a good description of checking the switches.
Thanks for your suggestions, life happened so now I’m getting back to it. I checked Nanocom and it did say AC Grant = YES. That led me to run a jumper cable to the compressor direct from the battery, no change. Then I checked the voltage on the compressor plug and it was 14.3. When I plugged the connector back into the compressor the clutch engaged and the AC started cooling. At idle the temp at the vents was 50 F with an ambient of 84 F. When I turned off the ignition and restarted it later, the AC cooled with the same results. Seems to just need a clutch rebuild.
Check the air gap on the clutch. It should be 16-30 thou and if over that it won't pull in. To adjust it, take the front off, remove one or two spacer washers and put it back.
One other possibility here is that the connection to ground was reestablished by disconnecting and reconnecting the discussed connector. Just a heads up here. These systems swithc both voltage and ground for compressor control. Ground is frequently overlooked. Ray
I am with Ray here......
If removing and re plugging the connector suddenly got it working, then that is the issue. Dirty contacts. Not the clutch, however as stated above, that is easy to check and repair as well.
Take the plug back apart, and give it a good clean up, tighten the connectors (Tweak with a small screwdriver tip) possibly a light application of silicone grease, and should be good to go!
The wiring of the ac unit is not corroded but still, it's not working properly, Any advice on whom to call either dealership or the air conditioning repair expert?
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