How we easily fixed our M3’s HVAC

David S.
Update by David S. Wallens to the BMW M3 project car
Feb 15, 2024 | BMW, M3, E46 M3, E46, hvac

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The fan blower worked when it wanted to.

Then it stopped blowing altogether.

It’s a BMW, so this is going to get complicated, right?

Fortunately, not.

Rennie of Redline Bimmer, as usual, diagnosed our issue over the phone: It’s the final stage unit, also known as the blower resistor. And also known, thanks to its appearance, as the hedgehog. It kind of lives back behind the glovebox.

The blower resistor, he said, is a common failure point on the E46-chassis BMW 3 Series.

BimmerWorld recommended the Behr replacement. It retails for about $35. They had it in stock.

We had it swapped out the last time the car was at Spiker Motorsports.

And now the fan works. All the time.

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David S. Wallens
David S. Wallens Editorial Director
2/15/24 11:49 a.m.

So, the PS here.

The paperwork that came with the car listed this part as already replaced. I’m friends with the previous owner (the one who replaced said part), so I asked him about it. It might have been a lower-priced option, he admitted. 

glyn ellis
glyn ellis New Reader
2/15/24 3:38 p.m.

Having done this job, I wouldn't call it simple. Access is a challenge unless you are a 14 yr old gymnast, and you can't see anything - basically everything was done by feel.

Noddaz GRM+ Memberand PowerDork
2/15/24 5:11 p.m.

In reply to glyn ellis :

But it was easy to replace.  GRM had someone else do it.  smiley

repoman New Reader
2/15/24 6:36 p.m.

I've done this on each of the 3 E46s I've owned and the one E39. Silly little part and a mild PITA to access but no real problem for me. The newer OE and BMW branded ones shouldn't fail again, the heat sink is better designed (lots more hedgehog pins)

glyn ellis
glyn ellis New Reader
2/16/24 10:04 a.m.

In reply to Noddaz :

Aaah - the one swipe (with Visa) maintenance method!

Tomwas1 New Reader
2/25/24 3:01 p.m.

Common e36 problem also. Contortionist required...!!! Just bought a 98 328 auto sedan from a friend built to msport spec over his 5 years of ownership...  Swapped it out just before giving me the car... Hes 32 in 72... Much easier for him...!!!

gunner (Forum Supporter)
gunner (Forum Supporter) GRM+ Memberand Dork
2/26/24 8:05 a.m.

Thats mildly reminiscent of the heater valve in the E28. Really easy to get to under the hood but not trouble free to replace, the aftermarket units were $10 a piece but required replacement roughly once a year, or buy the oem one for $100 and probably never have to replace it again. I went the oem route and it was still going strong when I sold it 6 years later. Worth every penny to no touch it again.

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