'90Q Climate control fan goes Hi or nothing

[FDRDippin]

What's up guys... I searched but haven't found my exact issue.

-2nd used climate control isn't working as it should.
-Intermittent display on first unit, so far no display on the second
-Both units will turn the fan on to the highest speed only, once on the highest speed, if I press the fan button again it goes off...not to low.
-while on the highest blowing speed if if press *any* other button on the climate control, it goes off.
-replaced the fan amplifier but symptoms still persist

Could this be two bad climate controls or a problem with the harness or something else?

90Q, 135k

"preciate ya.

[Q451990]

It sounds like two unrelated problems. The display problem and a bad fan control amplifier... except that you replaced the amp. Was it a used part? Did it work at all before failing? Lack of airflow across the amp will fry it in a matter of seconds.

Display Issues:
fix-for-1990-1993-q45-climate-controlle ... l#p5068572

Fan Amplifier:
how-to-fix-your-fan-control-amplifier-t433421-60.html

Good luck!

Heath

[Skibane]

Typically, if the fan amp blows, it no longer gives you the ability to turn the fan on and off - It either makes the fan run at full speed all the time the ignition switch is on (fails shorted), or the fan never runs at all (fails open).

It can't fail both open and shorted, so you never see a fan amp failure where you can make the fan run at full speed AND make it turn off completely.

So - The fan amp is unlikely to be your problem.

The climate control measures the voltage being delivered to the fan motor by the fan amp EXCEPT on maximum speed (in which case any voltage from the motor is ignored).

Personally, I'd suspect a problem with the harness or connectors - i.e., for some reason, the climate control isn't getting a voltage to measure from the fan.

[FDRDippin]

That's what i thought. I've had an amp fail before and it would only go off when the car was off. I ordered one from NISSAN yesterday anyway. I'll install it today to totally rule that out.

How would you approach testing the harness?
How difficult is it to replace the harness?
Any steps available to replace and where might be the best source for a replacement...Scottsdale?

[Skibane]

If you have an electrical test meter (digital multimeter), you could measure for continuity between the Fan Motor Feedback pin on your A/C Auto Amp and Pin 35 on your Fan Control Amp (area shaded in green below):



I don't have a wiring diagram for the G50 model, so I'm not 100 percent confident that the pin to the Auto Amp is actually Pin 34 as shown in the photo - If you can download a copy of the factory service manual, it will confirm which pin number you're looking for.

Basically, you're checking to see that there is still a solid connection between those two points. If the connection is still there, you'll measure continuity (less than several ohms of resistance) with your test meter. If the connection is broken somewhere, you'll measure a much higher resistance (hundreds or thousands of ohms).

Note that the ignition switch should be turned off when testing for continuity - You don't want to measure on a "live" circuit.