Heater fan issue - 2002 325i

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I have a 2002 325i and I guess it is just getting to that point where repairs are going to dog me. I recently posted about my oil light issue, thanks for all the responses but I also have two other issues. I think my
battery is getting towards the end and that;s an easy fix, just drop a new one in. Or is it? Will I need to have the module reset, or does that take care of itself? Also, I'd appreciate any recommendations for a new battery.
Item two is a bit more involved. The heater fan flucuates faster and slower and even runs when the car is turned off. (see previous problem - can you say dead battery? I had to roll start it tonight ) It has actually done this since the car was a year or so old, but it's more pronounced now and the battery has less reserve. At the time the BMW tech told me it was the wind or some such nonsense, but as usual, it wasn't real noticable. I don;t think that I'll have much luck having them cover a portion under warranty but I'll bring the repair order in anyhow. What would cause this with the heater fan?
Thanks in advance
Larry
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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.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Tue, 30 Oct 2007 09:55:13 +0000 (GMT), "Dave Plowman (News)"

But could the classic resistor failure cause the fan to run while the car is turned off?
/daytripper '00 s4 6spd
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wrote:

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

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On Tue, 30 Oct 2007 14:19:37 -0000, "R. Mark Clayton"

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
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wrote:

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.
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On Tue, 30 Oct 2007 17:17:26 -0000, "R. Mark Clayton"

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
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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.
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On Tue, 30 Oct 2007 19:13:41 +0000 (GMT), "Dave Plowman (News)"

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
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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?
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On Tue, 30 Oct 2007 23:25:01 +0000 (GMT), "Dave Plowman (News)"

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
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You didn't have a 'trunk' light or under 'hood' one? Either of these could stick on without you being aware.
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On Wed, 31 Oct 2007 20:01:58 +0000 (GMT), "Dave Plowman (News)"

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
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And extremely thirsty on petrol?

You seem to imply it's just BMW. Every car these days has electronics where once there was none. DIYers simply need to learn some new skills - perhaps also buy some new test equipment. In 50 years time or whatever the same will be said about today's vehicles.
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On Thu, 01 Nov 2007 10:05:41 +0000 (GMT), "Dave Plowman (News)"

Not really - fuel mileage on the 312ci engine was comparable to what you'd find on typical small-block V8s in trucks today. Otoh, there was absolutely zero emissions control back then - not even an EGR - so the exhaust plume was likely a few times greater than what today's technology provides.

Sorry - right after I posted that I realized you'd likely take my comments that way. I didn't mean to single out BMW - pretty much all current model cars and trucks have evolved to the same state where there's as many geegaws and doodads slathered on that manage to confound both owners and repair centers...
/daytripper '00 s4 6spd
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If there really was a demand for a no frills vehicle I'd guess it would be supplied. But even on the lower end of the used car market a fully loaded model always makes more than a basic one. So people obviously like toys.
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Button marked 'rest' on the heater panel. If the engine is hot it will run the heater with the ignition off.
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wrote:

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.
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daytripper wrote:

Yes.
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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
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