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 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. Haven't checked for a loose connector again but I am suspecting a open circuit in the coil again. I haven't changed the AC clutch yet but have no idea how the condition of the clutch would cause the coil to fail to open circuit. Both new coils ohmed out within spec before install. 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.

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.

Any ideas???

 

What about mechanical damage; something contacting and wearing or shorting through the coil wire? Any obvious signs of damage?

I would also check alternator output voltage. Perhaps high voltage might cause this problem.

I assuming you're doing this w/o discharging AC. If so, how are you accessing compressor clutch?

good luck

 

Absolutely nothing unusual about its condition. Looked like it was brand new. If the positive wire were to short to ground it would reduce the current going through the coil as there would be less resistance at the short and blow the 20 amp fuse at the source (fuse is good). If the ground wire were to short to ground nothing would happen. I also punctured the both wire's insulation right where it goes into the coil to exclude the possibility of loose wire terminals.

I have checked the voltage across the battery with the engine running and its normal (~13V). I'd also imagine voltage spikes in the charging system would cause many other issues. No other issues noted.

I am changing the solenoids without discharging the system. It can be done by unbolting the compressor from the mount and rotating the compressor so that the pulley point backwards slighly to enable pulley removal from the right wheel well (wheel well liner and windshield wiper reservoir removed). You'll need a pulley puller and an additional person to hold the compressor while removing and re-installing the pulley.

 

Your problem suggests you installed two faulty coils or something very unusual.

Why? No overvoltage or signs of damage. This means an internal flaw in coil opened up (vibration? or manufacturing flaw).

However, the coil actuation circuit is a single wire w/ ground through compressor to the engine. Any chance your compressor is not getting a good ground (paint perhaps preventing contact)? Ground path is from coil to compressor body to compressor mount, to engine. Anything in this path that would interupt ground would cause your problem. Maybe even a missing ground strap from engine to body?

good luck

 

The only thing I can come up with is that these are bad parts but they are OEM Honda coils. I've had this perception of Honda as high quality although I am aware of the TSX's (and other models) AC issues including the coils.

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 there were a grounding plane, a resistance between the air conditioner case ground and the engine or chassis ground (paint or corrosion), there would be less current going through the coil since there would be an additional resistance in series with the coil.

Luckily the dealer traded me out for the second coil so I've only paid for one coil so far. I'm trying to decide if its worth letting the dealer change it next so when the coils fails it'll be thier problem or keep trying to find the root cause.

 

Have you checked a loose failed coil by grounding to coil body and checking resistance at connector? This should also show open.

Hard to believe you got two bad coils, but it's possible, just very unlikely.

Let forum know how this story ends!

good luck

 

Just wanted to drop back in with the "fix" since I'm not a regular user.

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.

 

Update

The last solenoid coil made it a few weeks and then the compressor just came apart. There was a hole in the compressor case bigger than a quarter. One of the scrolls in the compress broke off the base plate. My theory is that the compressor was getting hot and causing the coil to short internally burn up and go open circuit.

Replaced the compressor, high pressure line, condenser, dryer, accessory belt, and cabin filter. $400 in parts from rock auto. No flush was done but there was no evidence of contamination. The ac has been working great for over a month now.

 

Thanks for followup.

I had simlar failure of scroll compressor on Subaru Forester. It stopped suddently and belt started squealing/smoking. I found the scroll plate had split at the center and crack had gradually progressed to part failed.

The scrolls apparently usually fail fairly benignly and don't spread shavings like a multi-cylinder compressor. That's helpful.

good luck