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Discussion Starter #1
Sorry long story...

2008 TSX w/ 90K miles

This started with the AC quitting a week ago. Used the OEM service manual to troubleshoot it to the AC solenoid coil (field coil). It was showing an open circuit right at the wires going into the coil. I have extensive automotive repair experience so I replaced it with a new one from the dealer no big deal. After less than 1 hour of use and maybe a dozen engine starts the AC quit again. I hoped the coil connector came unplugged. Nope, found an open circuit in the new coil. Thought maybe it was a bad part. Changed it again with a second new part. Failed again with less than an hour of operation. No loose connectors its an open circuit in the coil again. I haven't changed the AC clutch yet but have no idea how the condition of the clutch, with gap within tolerance, would cause the coil to fail to open circuit. Both new coils ohmed out within spec before install (~3.8ohms). When I removed the first new coil it still looked brand new, no wear marks from the pulley, the black paint and the coil "potting" had no signs of seeing high temps (brown, carbon, bubbles).

After reviewing the wiring diagram I have no idea how the condition of any of the rest of the AC system (charge pressures, high/low pressure switches, other HVAC controls) could "burn" up the coil. The coil gets its current (~3 amps) directly from the underhood relay through a 20 amp fuse directly from the battery.

I'm thinking about getting another new one and putting it on a DC power supply for 24 hours to see if it fails on the bench. I could also try to get one from a salvage yard that may/may not be from a differnt supplier and/or design.

If the positive wire were to short to ground it wouldnt draw more current going through the coil it would remain the same. The short would draw additional current blowing the 20 amp fuse at the source (fuse is good).


Battery and alternator voltage check good.

Any ideas???
 

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Not sure what ended up fixing the car but it has been working now for several weeks. Still thinking I got 2 bad solinoids, as unlikely as that seems. I bench tested the coil at 14V for 8 hours before installing it. The clutch was replaced and shimmed to the min clearance. I also installed a 4 amp fuse inline with the solinoid. The dealership was so sick of dealing with me that they kindly gave me a new relay and insisted that it may fix the problem so I put that in too.
 
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