A/C Fan intermittent

[abhibeckert]

The last couple of days the fan and aircon have become unreliable.

Sometimes it works perfect, sometimes it doesn't run until a few seconds after I start the car, sometimes it starts working 20 minutes into the drive and sometimes it never comes on.

The aircon seems to be working - if it's set to fresh air and I open the windows while driving that pulls a bit of air through and it's cold a/c.

Often driving over speed bumps it has started working suddenly and sometimes the fan works but at a significantly reduced speed. Which suggests it's a simple wiring issue.

I have a multimeter and kinda know how to use it - does anyone have any advice where I should start looking? Can I diagnose it further without pulling dashboard apart?

 

[Old.Tony]

Welcome to the forum.

There's a resistor module that lives in the air duct. On the D40 in Australia it's under the ducting on the left hand side - above where the front passenger's feet would be. Look for a module that's screwed in and about 50mm across and about 15mm or so thick. When it's removed, it will be like a credit card thick. This has been known to fail, I had to replace mine a couple of years ago.

That's what I'd look at first. Clean up its contacts and reinstall it to see if it fixes things, but if you notice a burned part of the board, it's probably worth replacing.

 

[abhibeckert]

Finally had time to investigate this morning and I'm pretty sure the resister is fine - there's power getting to it and it seems to have a sensible level of resistance.

So I guess the next thing is to check if the motor is grounded properly, then check if the motor actually works. I assume I can just run a wire from the battery to the motor to test that?

I have a Spanish built one and they seem quite expensive to replace, all the reasonably priced blower motors are for Thai built models.

Worst of all is we're in the middle of a heat wave (38°C and 70% humidity) so driving around without a fan is awful.

 

[bods]

Does the fan work on the maximum setting? This bypasses the resistor. If it doesn't, or only works intermittently on that setting too, then it you are on the right track with checking out the motor.

 

[abhibeckert]

Doesn’t work on any setting. It was cutting in and out for a while but is now completely off.

 

[ericcs]

can you short out the wires to the resistor to bypass it. that will rule that out!

 

[Old.Tony]

If the fan resistor appears to be ok, it might be as easy as pulling the fuse - try to the left of the glovebox, but if you can't find the A/C FAN there, it might be in the box near the ABS unit.

Erratic operation followed by failure is often just dirt/corrosion/arcing rather than a failing component.