Heater fan issue - 2002 325i

Only thing likely to need resetting is the radio station memory.

Your dealer is taking the p**s. You've got the 'standard' final stage resistor problem that plagues these cars. Mine has had two replacements. If it was under warranty demand they fix it. I can't believe they've never seen this problem before as it effects just about every car at some time.

But could the classic resistor failure cause the fan to run while the car is turned off?

/daytripper '00 s4 6spd

Er because it is connected to battery supply and lets current flow?

Yes.

Yes. It's actually a sort of hybrid module that melts down inside... there is always-on power inside the module and it can get shorted to the output.

When you replace the resistor pack, open up the old one and look inside. It's really a neat bit of technology... trouble is it isn't very reliable...

--scott

Errrr, on every car I've ever owned - and that goes back to a 1956 Ford, and up to a 2005 Durango - if the key isn't in the Run position there is no power to the HVAC system.

Does BMW source their electricals from Lucas? ;-)

/daytripper '00 s4 6spd

No kidding, but have you noticed how thinks like the interior lights, clock, seats etc. still work when the key is out of the ignition. These are the battery supply circuits, sometimes there may be more than one.

Bosch normally, but perhaps they made an exception for this unit.

Incidentally the auxiliary fan still works after the ignition is off too.

But then they didn't have the rather clever feature with the electric water pump that allows the heater to give output with the engine stopped and the keys removed. Like perhaps when leaving kids in the car for a moment while you pay for petrol etc. So to enable this the heater motor circuit requires 'permanent' power.

If only BMW/Bosch were as forthcoming with their circuit diagrams as Lucas were.

Certainly, but none of those are HVAC related, and none of them are downstream of the dropping resistor module...

Very common, but again, not HVAC, nor the dropping resistor...

/daytripper '00 s4 6spd

Ah - now that makes sense, though in the bargain it enables the problem that the OP has, and if it encourages parents to leave kids unattended in the car while they're doing something a bit more involved than just paying for fuel, it's not bright. A good tradeoff? I don't think so...

ahahahahaha!

/daytripper '00 s4 6spd

Button marked 'rest' on the heater panel. If the engine is hot it will run the heater with the ignition off.

I only used that as an example. I use it when parked up with the engine off. Very useful. Helps stop global warming. ;-) Plenty other things in the car are live with the engine off - and always have been, even in your '56 Ford. That would be the model with brakes and shocks extra?

ahahahaha! C'mon, try to stay somewhat serious ;-) The only things that would operate without the key in the run or accessory positions were the head/marker lights, interior dome light, and the clock. Little chance of running down the battery unless one wasn't paying attention when locking up - unlike the OP's problem, which could bite anyone without giving a hint in advance...

Progress? ahahahahahaha!

/daytripper '00 s4 6spd

I'm reading this with great interest - my 2001 325 has the same fluctuating fan issue - now I know what it is!!!

So where exactly is this resistor pack and is it diy-able? If the BMW part is so faulty (as I found out about their camshaft position sensors too...), does anyone have a replacement recommendation?

Thanks!!

Thanks for all the feedback. I don't think the blower would have drained my battery had it been healthy, but it was nearly toast anyhow. I found a Motorcraft 665 CCA replacement battery for $125 installed. That beats the $300 the dealer wanted. As for the blower, I'm bringing it in Thursday along with the repair order, where they looked at it before, and see what they say.

On the flip side, I managed to save a work mate $150 tonight by helping him install a turn signal bulb on his X5. That's right, the dealer quoted him an hour and a half for changing the front left turn bulb. Five bucks and a half hour later, he was on his way, with a spare bulb to boot.

Oh I forgot about this. Yes there is a way of getting the heater to continue to provide output once the car has stopped. You press [and hold?] the top left button IIRC (on a 2000 e38) and it will continue to heat the car for a while or till the engine goes cold.

You didn't have a 'trunk' light or under 'hood' one? Either of these could stick on without you being aware.

I think it's a special part and I've not seen it on sale outside a BMW dealer.

It's definitely DIYable on my E39 - it's situated on the bulkhead behind the heater (it's in the cool air intake to help its cooling) accessible via the (UK) driver's foot well. You have to remove the carpet strip on the transmission tunnel and the 'roof' of the foot well. And it's a bit of a fiddle. A LHD car is probably easier with more room due to no steering column in the way. But your 3 Series will likely differ in detail.

Nope. Neither one. This was an F100 panel truck, and there were very few features of any kind. Basic, trucky transportation.

And - in stark contrast to what's being sold today - dead simple to fix.

I can't even imagine what it's going to be like to keep up with all the problems that a few-year-old BMW will exhibit with all the bells and whistles that have been slathered on top of otherwise functional vehicles...

/daytripper '00 s4 6spd