A/C Compressor Field Coil

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The A/C in my TSX went out last week. I diagnosed it as a failed field coil. I ordered a new one (OEM Honda) and tore everything apart in preparation.

The new one arrived yesterday and I installed it. The A/C worked for five minutes and then quit again. I diagnosed it this morning again as a failed field coil. ?!???! Both coils show infinite resistance - break.

These field coils are simple electromagnets, so I would think there's little in there that could fail.

So, my question is, is there something up stream that could make these things fail, ie, what would destroy these? To me, it's just too coincidental that the original problem was a failed coil, and now I have a bad unit from Honda.
 
Originally Posted By: CT8
isn't there a diode in the coils?
Not that I know of. I test a lot of coils and they show the same resistance regardless of where I put my test leads
 
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The specs for this coil is 3.9-4.3 ohms. Out of the box the new one tested at 3.9.

I found this Four Seasons doc that details a test procedure for voltage drops at the connector during operation. I'll probably go down this road, as it says "An excessive drop in the available voltage can make the coil develop excessive heat, which
can lead to premature failure of the clutch. If the operational voltage is not correct, utilize the wiring diagram and voltage drop testing to find the cause of the excessive resistance." I can't imagine it would take only 5 minutes for this to occur, though, but who knows.
http://www.4s.com/Upload/Four%20Seasons/...COIL%20DIAG.PDF

I'd love to take it to a shop at this point if I felt I could trust somebody. I feel that I'm going to do more diagnosis on this than any local shop would - I just don't want the headache. I'm sure their first suggestion would be to replace to compressor.

I do know that I don't want to throw another $80 coil on it until I know what the problem is.
 
some of these have a thermal fuse inside.
if the clutch is slipping it can get hot enough to open it.
seen this on a saturn.
 
Low voltage by itself won't damage the coil. It could conceivably lead to slipping, which would burn everything up first, then finally the coil. This seems unlikely since you were there watching it operate normally and just stop.
 
13.2V/4Ohms = 3.3Amps. Before you install a new one, put a 5A fuse in-line with it first. You can also use a 12V tail-light bulb if you have one laying around. A DC ammeter would also be useful to see how much current is flowing in that ckt when you flip the switch.

I once installed a brand-spanking-new Bosch alternator in the sled, that once activated, it got so hot it turned the bright aluminum case a golden color! I asked the guy where I bought it to first check it on his machine. He said he didn't have the right cable set-up for it. (????) "Don't worry...it's good." He ate those words!

It CAN happen......
 
Originally Posted By: kc8adu
some of these have a thermal fuse inside.
if the clutch is slipping it can get hot enough to open it.
seen this on a saturn.


This compressor has a thermal switch in series with the refrigerant pressure switch and coil. Is that what you're talking about? Or some sort of fuse in the coil itself?
 
Are there any aftermarket sources for these things? Four Seasons doesn't list just the coil in their catalog and I can't find any other options besides Honda.
 
It could just be a bad part. I almost tore a transfer case apart when i got 2 bad shift motors in a row OE parts at that, two new ones and the original were all bad.
 
Originally Posted By: Trav
It could just be a bad part. I almost tore a transfer case apart when i got 2 bad shift motors in a row OE parts at that, two new ones and the original were all bad.


Thanks, Trav.

I would love for it to be a bad part. Two problems, though. No refunds on electronics and I'm going to have a tough time talking myself into putting a new on one there not really knowing if it really was a bad one or not...
laugh.gif
 
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Honda does have a history of bad ones. I think it was on CRVs where they extended the warranty for this part out to 120k. My two lasted 190k and 3 miles, respectively.
 
Originally Posted By: Trav
Any chance of a used one just to check and see if it runs longer than a few min?


Unfortunately, no. I've got two dead ones, though!
 
Originally Posted By: cpayne5
Originally Posted By: Trav
Any chance of a used one just to check and see if it runs longer than a few min?


Unfortunately, no. I've got two dead ones, though!


That really sucks, i feel the pain, been there done that, got the T shirt. Hours of trouble shooting that may turn out to be a bad new part.
I know some Honda models this vintage had a bad A/C clutch relay that caused all sort of voltage problems, i wonder if this could be an issue on this one?

The ones i have come across are marked omron G8HL-H71 1755A12A, the Intermotor (Standard) relay Part No. R6242 from AA is durable and only $6.
 
Are the junkyard near you broken? Personally, this is the type of thing where I would use a used or aftermarket part. $80 is way too much for just the coil. As to what the schematic would show, what does your factory service manual show?
 
Originally Posted By: Jetronic
a field coil isn't electronic though. Get your refund or replacement from the dealer you bought it from.


I should have said electrical, not electronic. In any case, I'm going to call them tomorrow to see if they can do anything.
 
Originally Posted By: zzyzzx
Are the junkyard near you broken? Personally, this is the type of thing where I would use a used or aftermarket part. $80 is way too much for just the coil. As to what the schematic would show, what does your factory service manual show?


This part number is specific to TSXs. Not many TSXs in the local yards. No yard around here will sell parts this small (they want to sell the entire compressor), and no pick a part yards have cars this new.
 
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