Climate Control Unit (CCU) - Capacitor Replacement and Repair

[Heineken]

A seemingly normal Climate Control Unit (CCU) with a fan working only in the max and off position came in from Switzerland.
The issue was confirmed in my own NSX with the self test not showing any issues just the fan not working as it should.
This usually points towards capacitor issues but when opening the unit it became obvious that the capacitors had already been replaced ..

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What was missed though was the mandatory acid removal.
Forgetting to do so will cause the destruction of the copper areas to continue underneath the PCB silk layer - until all acid is used up and the chemical process comes to a halt.

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First step is removal of the capacitors, cleaning the affected areas with a fibreglass pen down to bare medal.
Then checking for broken traces or missing copper with two cases identified:

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Adding a thin coat of solder, new capacitors (all dry electrolyte types) and various repair wires later the board was back in working condition.
I'm still impressed how much damage and abuse the CCU board can take before failing completely.

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After conformal coating and verifying operation in the vehicle I'm happy all is OK again and the CCU is ready to return home.

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In retrospective I'm suspecting that the missing copper around C11 (the second picture above) is what caused the fan control to stop working since it's near the responsible power transistor - maybe someone can confirm?

 

[Old Guy]

Eagle eyes! I am not sure that I would have caught those failed traces.

On a slightly related matter, have you ever dealt with a CCU where the blower will sometimes operate at low speed when the CCU is off? When I first turn my ignition key to the run position, if the CCU is off I can hear the fan operating on a very low speed. That fan speed is unaffected by the position of the fan speed control. If I start the car and then turn the CCU on and then turn the CCU off the fan will stop. After that, everything operates normally.

2-3 years ago I replaced all of the capacitors. None of the capacitors had developed leaks. The sneak fan operation existed before the capacitor replacement and persists after the fan replacement. What is slightly frustrating is that it will not do this sneak fan operation at start up consistently. Sometimes on start up if the CCU is off the fan does not run. That makes diagnosis challenging. I think the fan power transistor must be getting a sneak base signal from someplace. However, I have not been able to determine whether it is an actual PWM signal from the CCU or a small DC voltage of some kind that is just enough to turn the power transistor on.

It had been suggested that the sneak signal might be originating in the fan control unit. There was no obvious connection between the two systems; but, it was minimal work to confirm or refute the theory. On an occasion when I was experiencing this sneak fan run problem I removed the rear interior panels and completely disconnected the fan control unit and the sneak fan operation persisted which is what I expected.

The fact that I can power the CCU unit up and then turn it off and the sneak fan operation problem goes away has me mystified. It almost seems like a firmware glitch of some kind. Any thoughts on what might be causing this would be appreciated.

 

[Heineken]

To be honest, the second broken trace was discovered by my Fluke meter, but being short-sighted has advantages, sometimes :tongue:

When my own unit is re-installed I'll check for the sneak fan operation. It might really be a firmware bug since the interior fan is PWM controlled. If a stray voltage would activate the power transistor it would either run full speed or the transistor would heat up very quickly. If a true PWM is applied than the micro controller needs to run .. which would point to a firmware bug.

Maybe oscilloscoping the fan power wire during normal and sneak operation could yield some clues - a PWM signal will always have some sort of ripple ..

 

[Old Guy]

When winter goes away and I get my car out of storage, a scope on the circuit to the base on the power transistor was my next plan. If the the motor is running in PWM mode the base voltage should show that pretty clearly. I had the same thought about transistor heating if a stray base voltage was driving the the transistor partially on. Partially on is a bad place to be for a power transistor controlling a motor. The fact that the motor speed seems to be consistent whenever it occurs makes me think it is in PWM control because a stray base voltage would likely have variable motor speed. It would also be odd that the stray voltage would disappear when I power cycle the CCU.

The only thing that makes me a little crazy is the possibility that I am the only NSX owner with this bug, or perhaps the only owner that has noticed it?

 

[NSX2398]

The only thing that makes me a little crazy is the possibility that I am the only NSX owner with this bug, or perhaps the only owner that has noticed it?

I'm starting to wonder if I might the only one with a slightly different blower fan 'bug'. Mine started intermittently not working. It would typically not come on at all at startup with CCU on .. and changing the speed or CCU mode settings would not cause it to come on .. yet, it would occasionally magically come on during a drive and it seemed like maybe rough road or a bump would trigger it. So, on a couple of occasions when it wouldn't turn on after starting the car, I used a soft hammer to tap on the fan housing (under front hood) and it started up both times. I have been driving a lot on gravel roads lately so thought maybe some dust/debris was causing the fan to stick, but tonight I took the fan housing out of the car and no debris issues. The fan turned by hand and later by connecting to a battery. So, now I'm wondering if the brushes on the fan motor have maybe deteriorated to the point where it's not getting good contact. I've run this past BrianK and he doesn't think it's a CCU cap problem. Any other educated guesses? I'm a little shocked that a new fan motor MSRP is around $450 although online parts sites discount down to about $330 .. but that's still about $450 in Great White North dollars .. probably $500 with shipping.

 

[Old Guy]

$146 CD from Amayama plus shipping. Just need to make sure the part number is the same and that it is not one of those LHD - RHD specific parts

Honda 79310-SL0-013 (79310SL0013) MOTOR ASSY., BLOWER

Honda 79310-SL0-013 (79310SL0013) MOTOR ASSY., BLOWER. New & genuine Japanese car parts. Fast shipping. Low prices. Request a quote from Amayama Trading Co. online.

www.amayama.com

With the fan connected to the battery, try shaking the fan and tapping it to see if you can induce a momentary failure indicating an internal problem. Unfortunately, applying the battery and having the fan run is not a 100% definitive test. You can have a bad segment on the commutator. If the motor stops on that commutator segment it will not restart. Vibration can cause the armature to move slightly and bridge an adjacent segment allowing the motor to start. A more complete test is to mark the fan blade position and rotate the fan blade to allow a start attempt on every segment pair; but, you need to know the number of segments and angular separation to that and it is a lot of work.

If the motor stops running while it is switched on, then the problem is likely not a bad commutator. However, it the problem is that the motor randomly fails to start I expect a commutator problem. If you are keen to explore, you could pull the motor apart to examine the brushes and commutator which would be the likely wear candidates. There was a thread a couple of years ago discussing the rebuild of the condenser fan motors which included a link to a source for replacement brushes. You could also examine the commutator for damage and check the commutator - armature connections with an ohmmeter. A commutator that shows mild damage may be salvageable.

If the motor stops randomly a bad connection on the motor pigtail or in the wiring harness could be your problem. If the problem is confined to randomly failing to start, then I think the motor is the problem and it's probably a bad commutator segment.

 

[NSX2398]

If the problem is confined to randomly failing to start, then I think the motor is the problem and it's probably a bad commutator segment.

Sorry for not replying sooner .. it's been a bit of an adventure. For some reason, I'm not being notified of replies to my posts and by the time I saw your post, I had already ordered a new blower as I had come to the same conclusion as you did in the above comment. And since I have over 200k miles on the car .. and hence the blower, .. it was time for a replacement. Unfortunately, my local dealer parts guy told me that there were none in Canada and backordered to Jan or Feb. So, I contacted one of the websites which adverse Acura OEM parts (and happens to also be a US Acura dealer) and he said that there were none in the national parts warehouse but was nice enough to point me to two dealers who had one in stock. So, I contacted the closest one who confirmed they did still actually have it in stock .. unfortunately he wanted full retail ($538) and said they wouldn't ship to Canada. I've used a package delivery service in Plentywood before so had the part within a week. Everything seem to be good .. not exactly the same motor visually but it was in a bag with the correct part#.

Then the fun started. The motor swap was pretty straightforward but after getting everything back together, the blower wasn't working .. so I launched into the blower diagnostic routine in the shop manual. I hadn't gone through this originally because it was intermittent and did work sometimes .. but felt I had to now in case I'd blown a fuse or had a flakey relay. Many steps later, I get to the one which gets you to unplug the power connector and apply power directly to the blower. To my surprise, it doesn't come on .. diagnostic advice: replace the blower! I probably should have tested it when I unpacked the part.

Anyway, after uninstalling everything again, I pull the motor out and figure it must be in the wiring between the motor and the connector. Nope. So I pulled the motor apart and discover that the wiring is not connected to the brushes. There's a kind of crimp connector which I presume is what holds the lead wire and brush wire together but no evidence of any solder and the crimp wasn't tight enough to hold the wires on either brush. So, pretty shoddy build quality. So, to make a long story short, I loosened the crimp and then recrimped the wires before adding some solder to the connection. After re-installing everything, I now have airflow in the cabin .. which is a prerequisite for heat and defrost which is now badly needed in our -10C weather. Took it out for a quick checkout test drive and now that we have snow again, I enjoyed the drive.

So tks for your comments about commutator trouble-shooting. I took apart the old motor and there was still some brush length left but the commutator was pretty worn so not sure I'd have wanted to rebuild things. Tks too for sniffing out a potentially cheaper alternative motor .. although that site says it's only a possible match and the parts diagram didn't seem to be that close to I'm not sure I would have risked it .. even though I'm sure there's a lot of overlap between Honda and Acura blower motors.

Take care ... Ian

 

[Old Guy]

That is a bitter pill, paying a premium price for a poorly assembled product; but, good that it is sorted and you have the all-important heat functional again.