'93 325is Heater Blower Resistor Fails Repeatedly

[swanage]

Howdy,

I recently rescued a 1993 325is from a fairly negligent owner, among the things he let go was the heater blower resistor (symptom: heater only blows on switch 4). I pulled apart the dash and pulled out the old resistor and replaced it with the proper part and had the blower working again and thermostaticly controlled with the climate controls. However this only lasted about a day, and now the car once again only blows on setting 4. I'm pretty sure the new resistor pack is fried.

Anyone have any ideas/advice on why they're failing and what I can do in terms of detecting/fixing the problem? I'm a little paranoid that perhaps the cooling system is contaminated and I'm frying it out with voltage shorting through that, but I've got no bmw experience at all so I'm just basing that off what I heard (planning on doing a cooling flush soon regardless).

Any help would be much appreciated, thanks!

[Kalevera]

Those resistor packs have a 100% failure rate on the early cars. If the replacement part wasn't a brand new OE part, I'd recommend buying a new one and installing it.

The coolant/engine cooling system has little to do with how the resistor pack is cooled -- how old is the microfilter? Any significant buildup of dust or debris in the air box?

And, for what it's worth, it should take about 15 minutes to replace it. Pulll the DS bolster cover (4 screws, if I recall correctly, and a bit of careful tugging to get the outboard side clip out of the dash in one piece), replace the resistor pack (should be a Torx T15, if memory serves), put it all back together once it's confirmed to be working.

Good luck!

best, whit

[winfred]

if theres no air blockage maybe the blower motor is shot and drawing too many amps, if this is the case it may of took out the thermal fuse on the new resister pack, you can solder in a blade style fuse to save the new resister

[swanage]

Those resistor packs have a 100% failure rate on the early cars. If the replacement part wasn't a brand new OE part, I'd recommend buying a new one and installing it.

I got a brand new part from the local stealer, and it did work for a short period of time.


The coolant/engine cooling system has little to do with how the resistor pack is cooled
I wasn't so worried about cooling the resistor as the cooling system providing an electrical short that would be frying the resistors.

-- how old is the microfilter? Any significant buildup of dust or debris in the air box?

As I said I just got the car, so this will be the next thing up that I'll be checking before I try another new part.

The replacement definitely is easy so I'm not worried about that but I'm definitely not planning on burning one of these out on a daily basis, which is the real problem I have.