Climate control unit still dead after replacing capacitors

[Chris Yewdall]

Spent some time trying to fix a dead a/c unit recently. I purchased all the caps and desoldered, resoldered the new ones with the correct polarity. Dropped it in the dash and reconnected and nothing.

I then continuity checked all the fuses in the 3 fuse boxes and they're all fine.

I then buzzed through all the various connections/tracks on the underside of the climate control unit circuit board and no signs of any broken tracks. There had been some minor leakage from the old caps onto the board, however this doesn't appear to have damaged the integrity of the board connections.

I did notice that there is a capacitor on the smaller circuit board that is mounted in the digital display head unit for the climate control - has anyone ever had to replace this one.

I am in the process of obtaining an EV meter to confirm the capacitance of the new caps but wondered if anyone had come across this before after changing out the caps which seems to be the typical cause of climate control system failure.

I do have power to the board since the blower fan started up when I was checking the voltage on the upper right hand set of pins on the 28 pin connector.

 

[MOMSPH]

Brian of http://nsxe-repair.com/Repairsrv.html fixed mine as well as other many primers CC unit.

 

[JD Cross]

Send it to Briank.
If your Bose amps haven't been done, send those too.

 

[Old Guy]

I have never had the dead CCU problem so I have no direct experience. That said, since you were reinstalling new electrolytic capacitors, you insured that the polarities were correct?

Oops - just noticed that you said the polarities were correct

 

[ftuhy]

^ +1 on that. Also, when some of the capacitors fail, they can blow out paths on the printed circuit board. This is particularly true for C44. Finding evidence of where the path was can be a challenge, making the full repair difficult. But, again, BrianK is the expert at that.

Note that the heart of the problem was poor circuit design that causes the capacitors to blow. Regardless of what replacement capacitors are used, they eventually will blow again after a number of years. The three that fail most often are C44, C11 and C32. Because C44 especially damages the circuit board, I would place a teflon washer under it to help prevent further damage the next time it blows.

As to the Bose amps, I've never had a problem on my '96 (or on my 1984 Corvette's Bose system). I wonder if certain years were more prone to that failure?

 

[Old Guy]

A couple of thoughts on your problem. Did you replace the capacitors because the CCU stopped working and there was evidence of a failed capacitor(s) or did theCCU stop working and you replaced the capacitors because that is what everybody says is the solution? If the latter, then the original problem may not be the capacitors. You could have something like a failed power up circuit (the on-off button has ceased to operate). If you had electrolyte puffing out of the capacitors, then capacitor replacement should have been the path to the solution (assuming no peripheral damage).

You said that you had power to the board because the blower started up when you were checking the pin terminations. About the only way that you can get the blower to start up with the CCU out is by grounding pin 22 which would cause the blower to operate at high speed. That is not a guarantee that you have 12v to the CCU. You should confirm that you have 12v on pins 27, 28 and 30 and also on pin 11 if the tail light relay is actuated (go figure!). You should also confirm grounds on pins 24 and 25.

Honda does not provide a test procedure for the CCU and I don’t have access to any circuit diagrams for the CCU so I can’t provide any more definitive advice.

 

[hofffam]

I did what the OP did because my CCU had some of the same symptoms as others (fan only operated on high, etc.). But after replacing all caps, it still didn't work.

Sent it to BrianK. It came back and worked fine. No new caps. But I did see new bypasses on the circuit board, which repaired copper traces that probably had failed (probably from leaking caps). I do not have the ability to diagnose which were bad. My only beef is that BrianK charged me full price without having to replace a single cap.

 

[Miner]

My only beef is that BrianK charged me full price without having to replace a single cap.

There is an old story about a plumber. BrianK fixes the control board for a fee. Since it is more reasonable than a new board, and more reliable, and he is able to repair the board, I'd say he saved you the cost of a new board.

 

[jcbadcura]

+1 for BrianK and his services.

 

[Briank]

I always replace the caps even if they have been replaced before I get the board. I have to get them out of the way to do a proper repair. Its actually more work to fix a molested board because it can have repair induced problems along with the normal issues I see.