My cabin fan works great when I step on the brakes. Sometimes. When it is working it seems to function normally; there is no strange noise and the heater or A/C works well. When I'm driving the fan may or may not work, and sometimes varies its speed regardless of anything I do. Mostly if I step on the brakes to slow or stop, the fan comes on to its nominal speed. But not always.

It doesn't matter whether or not the fan speed control is on Auto or manual. When I first start the car, the fan may or may not work, but if it doesn't, it usually kicks in when I stop at the end of my street.

I am constantly adjusting the windows to correct for the problem, which is very unsafe.

If you know anything about where to start looking for this problem or have a similar experience, please help.

Thanks!
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98 V70 GLT black 54k

hello,
odd problem you have there! ....do the led lights on the heater control panel buttons flash when you first start the car? if they do then there is a fault code recorded in the climate control module (assuming you have auto air con.)
having a dealer read these faults would give an idea of the problem.
two common problems on old v70's are worn out fan motor which draws too much current and stops working intermittantly, and faulty fan power stage module.
i cant think how any fan problems would relate to the brake pedal but cars are like that sometimes...

steve.

The LED lights on the buttons do not flash a code. Still it could be logic related since the fan speed is probably controlled logically (even in manual) and stepping on the brake possibly creates a power spike or logic state of its own. (?)

Then again stepping on the brake also creates a kinetic condition on the fan itself or wiring.

But right now I don't have a clue where to start looking for the fault. I could take it to a dealer or indy, but not if they aren't going to know where to look. Plus it would work perfectly that day ;)

Is this climate control module located in the dash? How about the fan power stage module? I have a vague idea that the fan itself is near the passenger knees, and probably complicated to get to. But I should rule out mechanical problems first. Maybe debris is leaning away from the fan when I stop. I have changed the pollen filter but still something could be in there. Or wire contacts could be corroded?

Thanks!
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98 V70 GLT black 54k