Hi,

The interior heater fan speed in my 2003 Volvo S40 is erratic. For example, when I turn the fan speed dial to 1, and for a split second it revs up very high, then settles into a lower fan speed, but then sometimes the speed revs up again.

I had the CEL code read at O'Reilly Auto Parts (for engine misfire), and they told me there was a "0045" code related to "blower fan". I googled "Volvo 0045 blower fan", and found:

Quote:

CCM-0045 Blower fan relay. Signal too high

at https://www.volvoforums.org.uk/showthread.php?t=81259

Is a bad blower fan relay what's responsible for the erratic fan speeds?

If so, I think I have to do something like this?


Despite the title... looks like fairly difficult work ... for a novice, anyway. I just wanted to be as sure as possible before I devote time into this ... usually simple fixes turn into giant messes for me.

Thanks.

 

Common issue. Replacing the blower motor resistor/transistor may or may not fix the erratic blower issue. For some it has, others not. Worth a try as a process of elimination and cost around $35. Odds are it is the actual blower motor creating the problem, you can get one on rockauto.com or maybe track down a unit in the wrecker. Perhaps just live with it until you can track down a cheap replacement or until it dies completely.

 

2N3055NPNTransistor

 

Another thought is some electrical contact cleaner. My radio station dial pot was wonky, jumpy around and not holding a station. Pulled the **** (key off), sprayed the cleaner down the shaft, turned the shaft a few times, sprayed again. Let it dry and replaced the **** and voila. Working like a charm. Did the same to the blower fan pot after replacing the blower fan transistor unit and still getting erratic blower fan speeds. All is good now.

 

This is the same fix that we used to use "back in the day" to fix scratchy volume controls (you remember - you'd get a horrible, grinding static when you twisted the volume ****).

The potentiometer (variable value resistor, actually) have a substrate that contains the resistive material in an arc, and it relies on the point of a lightly-tensioned copper arm making good contact on that arc. Any number of environmental factors can cause a light build-up of stuff on top of that resistive layer, which causes intermittent connection to the copper arm. Spraying the cleaner in (even if indirectly) will usually loosen and dissolve the gunk enough that it will be displaced by the contact point as it "plows" back and forth through the gunk (done before the cleaner dries out). Ideally, the spray will wash it all off the surface of the resistor material, and out of the potentiometer, where it'll never be a problem again. Some of the cleaner contains a light lube that will (hopefully) prevent the build-up of new gunk.