Built in Diags for e46?

If the blower speed has a mind of its own - or sometimes doesn't run at all or goes to full - while the speed display is normal, 99.99% the final stage resistor. In auto, however, it does vary its speed until near the correct temp is reached. And on a cold day after a cold start if heat is called for it won't blow hard until the engine warms up.

Not sure if it throws an OBD fault code for this case, if it does, you can read that error if you have an OBD scanner (there's a 20pin OBDII port in the footwell at the driver side)

No OBD codes - those are for emissions components and systems only.

Replacement is the test for this component. There are tests you can do with a dedicated computer/BMW-code scanning tool - but since these tools start at $500 - that makes buying one for this test not a rational thing to do. A dealer could diagnose it for you - cost is typically 1 hour labor - which in the US is running from $100-125/hour. Again - not a rational thing to do with a $40 part.

Given the behavior you describe - as Dave said - its about 99% certain it's the final-stage-resistor.

Thanks all for your suggestions. The symptoms are very much the same as has been described, so I guess I'll just get the part and see.

Brian, you say it's a $40 part. Do you know where you saw that price? Everything I see is about $65 and up....

Sorry, it was admin that said it, not Brian.

Sorry, that was admin, not Brian.

Try visiting

Very cool. Thanks!