Climate Control Fan Always On?

[DrexNX]

Just picked up my R32 from the port on friday, and it's got a strange issue - it came with a climate control unit where the screen didn't work so I wasn't bothered by the fan always running. But now I've replaced the unit, and the fan just runs continuously; it changes speed correctly, and the mode actuators all work to change the output locations. The ambient temperature sensor works too, but it seems like hitting the off button just turns the screen off - the fan stays on as long as the key is in ACC or ON no matter what I do

am I missing something or is there something wrong? a search turned up a lot of thread about AC not working, blend door actuator problems, sensor faults, etc. but nothing like what I'm seeing.

[89CAL]

Your talking about the blower fan that blows the air around inside the car? There is an issue there, it sounds like wiring to me. By changing the unit I'd happily rule it out as the problem so its after that. Im not sure how it controls fan speed, looks like it does it through a fan control amp in the R33, I dont have an R32 wiring diagram on me.

In terms of R33 the fan is powered direct from a fuse (ACC), tees to the amp and then must be grounded through the HVAC unit, so because everything else works (door actuators etc) and im assuming the problem is either that your blower fan has incorrect wiring (earthed straight after the fan by someone or by a wire rub through etc) or the Amp might be wrecked (if it has one like the 33 does)

Best bet is to trace some wires around the fan

[DrexNX]

after reading through the service manual, it does appear to use a computer-controlled fan motor amp as the R33 does - not something I'd expect for a car that debuted in 1989!

a shorted or stuck relay in that unit would explain the constant fan power, I'll have to dick around with it when I get a chance. I wish they'd provide pin to pin resistances to check it easily without having to rig up a test setup, but not everything can be as easy as a mid-90s Honda

[DrexNX]

a quick FAST lookup shows it as key 27177, PN 27761-01U00, for anyone in the future that stumbles upon this

[DrexNX]

small update on this, my car was missing the second 15A blower motor fuse out the fusebox (not even blown, just straight missing) and replacing that got my fan speed 4 back, but now it only seems to either give me speed 3 or speed 4.

[DrexNX]

I did some research about fixing the fan amp - turns out they're pretty simple devices, just a thermal protection diode and a darlington transistor. I couldn't bear paying $150+ for another one when I'm good with a soldering iron, so here's a guide on how to fix the issue:

take off the glovebox (all the screws are obvious) and take out the metal bracket in the center here.

Pry the unit apart and check the resistance of the 2nd and 3rd leg of the transistor - if you get any value other than infinite/open circuit, you need a new one. Ebay it, its long obsolete.

as you can see, I'm only getting 3 ohms with no power from collector to emitter = transistor is f**ked.

If your fan never runs, its probably because the thermal protection diode is cooked. Mine was fine though.

R33+ most likely went to a MOSFET which is what nissan *should* have used on the R32s as well - guess an old guy designed this fan amp, darlingtons were oldschool even in 1989!

Edited May 31, 2016 by DrexNX

[avarvelo]

My sons air stopped working in his R33. This thread led me to this. So I added a little bit of solder on the pad and sunk the tab down into the bubble. Hope fully this will help someone.  Ac is as good as new. Thank you