91 Climate Control - CCU Replaced - Blower Stuck on

[captnsx]

I bought my NSX about 4 Months ago, one of the pending items needing to be addressed when I bought it was the Climate control issue. I was hoping the problem would be related to a simple CCU repair, unfortunately that only seems to be part of the issue.

I sent my CCU out to SOS for repair, they sent it back to me saying it was not repairable. I then found a company (ASI, www.autoecu.com) who was willing to repair the unit for me. I finally got the unit back in, and all the functions seem to be working, except the fan is stuck on ~80% power, always. When I rotate the fan control to full, I do hear a slight change in the fan speed, but anywhere between off, and 3/4 speed, it will run at 80%. My only option to shut the blower off is to pull the blower relay.

I had thought the problem may lie in the power transistor, so I checked the 3 pin plug at the transistor, and was looking for and have full 12.5v at the blk/blu, and 0v at the Grn/blk, regardless of the fan speed selector position. This makes me seem to believe the CCU is still bad, however, I just got it back from AutoECU and everything checked out on their end.

Any ideas before I go soldering in a new power transistor?

As always, help and input is much appreciated! Thanks guys.

 

[FF Drifter]

BrianK is the best service provider for repairing your CCU: http://nsxe-repair.com/Climate.html

 

[captnsx]

BrianK is the best service provider for repairing your CCU: http://nsxe-repair.com/Climate.html

I spoke to briank about this issue before I did my own diagnostics at the power transistor plug, and I hear he does the repairs for SOS, who said my unit was not repairable.

AutoECU offers warranty on their work, but I am tired of taking this thing in and out!

 

[DocL]

I spoke to briank about this issue before I did my own diagnostics at the power transistor plug, and I hear he does the repairs for SOS, who said my unit was not repairable.

AutoECU offers warranty on their work, but I am tired of taking this thing in and out!

So you sent your CCU to the best of the best, and they told you it couldn't be repaired. Then you find a company online who says they can fix it without the knowledge that you already had. I think it is unfair for you to claim that they should warranty their work on something that you already knew was FUBAR.

Your best bet at this point is waiting until one shows up here on the marketplace, or you need to pony up the $$$ and buy a new one from the dealer.

 

[captnsx]

So you sent your CCU to the best of the best, and they told you it couldn't be repaired. Then you find a company online who says they can fix it without the knowledge that you already had. I think it is unfair for you to claim that they should warranty their work on something that you already knew was FUBAR.

Your best bet at this point is waiting until one shows up here on the marketplace, or you need to pony up the $$$ and buy a new one from the dealer.

The question was in the diagnosis of the part, that is all. It would be senseless to waste Brian's time diagnosing a unit that was already repaired, and also equally senseless to replace a part that wasn't faulty when a $10 transistor can fix the issue. I could email this directly to BrianK, but I think it is valuable to keep these types of things on the forum for anyone else who may have a similar issue, that is a great benefit of the forum.

The transistor has 3 wires, from what I can tell, voltage in (12.5), voltage out (0v), and ground. I am curious how the fan can run at 80% power if the voltage out is 0v? or, does the voltage on the blk/grn wire need to be measured with the connector plugged into the transistor? is the 3-9v signal on the BLK/GRN wire supplied by the transistor or by the CCU itself?

Thanks again all.

 

[Old Guy]

I had thought the problem may lie in the power transistor, so I checked the 3 pin plug at the transistor, and was looking for and have full 12.5v at the blk/blu, and 0v at the Grn/blk, regardless of the fan speed selector position. This makes me seem to believe the CCU is still bad, however, I just got it back from AutoECU and everything checked out on their end.

Any ideas before I go soldering in a new power transistor?

As always, help and input is much appreciated! Thanks guys.

Refer to the attached wiring diagram for the blower motor. With the transistor disconnected and if the CCU blower speed is set to something other than 0, you should have the full 12v on black / blue wire. The blower motor speed is controlled by pulse width modulation of the power transistor which is just acting as a high speed on/off switch. The transistor is switched on or off by the signal from the CCU on the green/black wire. When the blower is switched on to the high setting, the blower high relay closes and by-passes the power transistor completely.

I am going to speculate (because I have not pulled the CCU apart to do measurements), that the voltage signal on the green / black wire is a pulse width modulated offset square wave. The switching frequency stays constant but the width of the pulses increases to increase the average voltage applied to the motor. In order to measure the voltage on the green / black wire, you really need an oscilloscope to measure the waveform. A galvanometer style voltmeter or even a digital voltmeter (depending on the sampling / calculation technique) may give no or a definitely incorrect response with the PWM signal. Also, note that with the power transistor connected, the voltage that you would measure on the green black wire is going to be really small, way less than 1 volt as it is just the forward base to emitter voltage required to switch the power transistor on.

If the blower is running and the blower hi relay is not energized, the power transistor must be passing current. In order for this to happen, it must be getting a signal switching it on (via the green black wire) or the power transistor collector (black / blue wire) has shorted internally to the emitter (black wire). If you can arrange to just disconnect the green / black wire and the blower continues to operate, the power transistor has shorted (I have never heard of that happening!). If the blower quits when you disconnect the wire, then the power transistor is OK and the CCU is not modulating the signal on the green / black wire to switch the power transistor, perhaps being stuck at the full output. In such case you should send the CCU back to the company that claimed that they repaired it.

Again, the best way to confirm non-operation of the blower output control on the CCU would be to use an oscilloscope to look for the pulse width control signal on the green / black wire. If it is operating properly, it should look like an offset square wave whose width increases as the blower speed setting is increased on the CCU. In the absence of an oscilloscope, you can try the test method discussed above.

 

[captnsx]

Exactly what I was looking for, thanks much! I will diagnose and report back with findings.

The FSM procedure located here;

http://www.justanswer.com/uploads/dinotapia/2009-05-20_180902_nsx_blower.pdf

Is assuming you can see a voltage with a DMM on the grn/blk wire, coming from the CCU output, however, when I test I always get 0v, even though my blower is running ( and the switch is on half, not full ). I just wanted to make sure I wasn't doing something wrong with my procedure, thanks for clearing it up better than the FSM!

 

[Old Guy]

The factory test procedure is a little bit confusing. First off, it applies specifically to the case where the blower only runs when the switch is in the high position. My understanding is that yours runs in other switch positions, you just don't get any speed control. A quick test would be to pull the blower high relay, if the blower does not run at all, then the blower is only getting power when the hi relay closes which is slightly different than what you describe.

After reading it a couple of times, the test procedure checks for voltage on the output of the green / black wire from the CCU with the blower transistor disconnected. In such case, with the power transistor disconnected, the voltage is not clamped to the forward bias voltage of the power transistor and it could be as described in the test procedure (6 - 7 volts) depending on the design of the power transistor driver circuit in the CCU. From your test description in your first post, I took it that you were measuring the voltage on the green / black wire by back probing it while the blower motor was operating. In such case, with the transistor connected there is no way that you could have 6 - 7 volts on the green / black wire as it would be clamped by the forward base to emitter voltage on the power transistor.

Try measuring the output voltage of the CCU on the green / black wire with the power transistor disconnected. I am still a little up in the air as to what you will measure with the multi meter. I don't think it can be zero because there has to be a signal there to switch the power transistor on to run the fan (unless the power transistor is shorted as I noted in my previous post).