Blower only works on high

[jeffnhiscars]

2 kinds Ian Magna and a bosch Magna has fixed wires Bosch doesnt

Those sound like the aux fan resistors whereas the OP needs one for the HVAC blower

[reelizmpro]

if the motor brushes are worn it will work intermitently and probably make some noises before stop working altogether. The resistor pack is not a resistor at all but a set of solid state coils that have different resistances. They don't go bad per se, but the contacts where it meets the blower fan often corrodes and needs a good cleaning or resurfacing.

[idickers]

if the motor brushes are worn it will work intermitently and probably make some noises before stop working altogether. The resistor pack is not a resistor at all but a set of solid state coils that have different resistances. They don't go bad per se, but the contacts where it meets the blower fan often corrodes and needs a good cleaning or resurfacing.

I haven't worked on this resistor pack before. Can I see it after I remove the plastic housing from the engine bay, with the blower squirrel cage still installed?

[oldmann]

I haven't worked on this resistor pack before. Can I see it after I remove the plastic housing from the engine bay, with the blower squirrel cage still installed?

Plastic cover and wiring out of the way, Then the metal cover over the blower itself can come off, the resistor coils are just inside, the motor plugs into the resistors. PITA but while your in there replace the blower too, you don't want to do this again.

[jeffnhiscars]

My blower only works on high as well and I have a resistor on the way since that seemed to be the consensus $27 from autohausaz). I believe there are 4 contacts which I assume to be one for each speed so you would think corrosion would cause a variety of working\non-working speeds rather than just the "4th only".

Good suggestion to check the brushes and contacts of course.

[idickers]

My blower only works on high as well and I have a resistor on the way since that seemed to be the consensus $27 from autohausaz).

What was the part # for the resistor you ordered?

[jeffnhiscars]

What was the part # for the resistor you ordered?

64111468521

IIRC its "OEM Behr"

[reelizmpro]

My blower only works on high as well and I have a resistor on the way since that seemed to be the consensus $27 from autohausaz). I believe there are 4 contacts which I assume to be one for each speed so you would think corrosion would cause a variety of working\non-working speeds rather than just the "4th only".

Good suggestion to check the brushes and contacts of course.

Why do u think there is a resistor pack in the first place? Think about it. Max speed is straight through, no resistance because its just ON. A new board will solve your problem but it woulda been a simple fix. Corrosion wasn't a good term, its more like oxidation.

[jeffnhiscars]

Why do u think there is a resistor pack in the first place? Think about it. Max speed is straight through, no resistance because its just ON. A new board will solve your problem but it woulda been a simple fix. Corrosion wasn't a good term, its more like oxidation.

I'm not sure I see your point or what you mean by "it would have been a simple fix"

Here's the realoem diagram showing the resistor as #5 so it certainly exists in at least some applications and this particular diagram is based on my VIN.

http://www.realoem.com/bmw/showparts.do?model=BB23&mospid=47326&btnr=64_1719&hg=64&fg=35

As to the corrosion\oxidation point, I try to keep my terms similar to the post Im responding to keep it easier to follow the train of thought. The fact is, that while corrosion is the result of a chemical reaction, oxidation is considered a form of corrosion, although obviously with oxygen vs some other chemical so they are reasonably interchangeable in this conversation.

Something steps down the amperage to create different fan speeds. Its either in the switch or via a separate device, much the same as with the aux fan resistor. Having read more than one thread about a "high speed only" blower being fixed by a new resistor (or resistor pack if you prefer), I ordered one on spec since I was ordering a hood and trunk strut to keep them from falling on my head and they werent enough to get me free shipping.

Not sure if this addresses your point but its early so maybe Im just blathering :)

[reelizmpro]

I misread what you were saying in your post last night. I was reading off and on from my phone while at work. You didn't have to buy another resistor is my point just resurface the contacts. It's worked for me for several years. Sure a new board will fix it (if the motor isn't on the way out too) but not because the old one is "bad." I felt that oxidation was a more accurate description because the contacts look fine when you remove the pack. It would help to spray some contact cleaner in the motor before installing the board. Goodluck.

[Quadrajet]

It's so ridiculously simple to do what reeliz is suggesting. I took some 400grit wet or dry, folded it over and dragged it thru the contacts like 3 or 4 times and was done. Of course it took way more time to get to the unit and reassemble it again.

[reelizmpro]

This is one of those things where...you can fix the part but shops typically will just replace it. For shops it makes more sense to simply sell and replace the resistor or entire blower motor for that matter. But for the BMW DIY owner who knows how to do the job, it's worthwhile to clean the contacts and save their money. They may need it for another blower motor later when the brushes go bad.

[jeffnhiscars]

I misread what you were saying in your post last night. I was reading off and on from my phone while at work. You didn't have to buy another resistor is my point just resurface the contacts. It's worked for me for several years. Sure a new board will fix it (if the motor isn't on the way out too) but not because the old one is "bad." I felt that oxidation was a more accurate description because the contacts look fine when you remove the pack. It would help to spray some contact cleaner in the motor before installing the board. Goodluck.

It's so ridiculously simple to do what reeliz is suggesting. I took some 400grit wet or dry, folded it over and dragged it thru the contacts like 3 or 4 times and was done. Of course it took way more time to get to the unit and reassemble it again.

Barry I often misread the 32nd post in a thread so I understand.

I have no problem servicing anything and in some cases will fix things that arent intended to be fixed. I've done enough speedo gears & window switches etc etc. In this case I took the lazy route and did not fully explore the blower resistor mostly cause it made sense to me that it was blown since with 4 speeds it seemed unllikely that the same 3 contacts (1-3) would oxidize in a number of cases while 4 always remained working.

I also thought since I do have to take the damn thing out regardless, I may as well have the replacement on hand. Besides the free shipping, curiosity came in to play as this is probably one of the few parts I have never touched on an e30..lol

When I get it out I will surely clean it and if it works Ill have a new spare for when one of the 3 other e30's in the driveway needs one (well really 2 since the 84 318i only has a 3 spd ).

IF, however, the resistor is blown, how do you guys like your crow served ? :giggle:

[Quadrajet]

I just shoot crows myself;)

I've done the clean and replace on 3 or 4 BMW's now. Not to say your's couldn't be blown, if it is, then maybe it's been cleaned 4 times already.

[reelizmpro]

That's my other point...it cannot be blown. It's just solid state coils! It'll work provided the circuit isn't open and the contacts make a good connection. It's not a traditional resistor pack like the aux fan resistor.

As for why it works on 4 and not any of the lower speeds...this is my theory:

Ohms Law : i=v/r

We see that current decreases as resistance increases. Max speed position 4 has virtually no resistance therefore you have max current, position 3 has a little resistance, position 2 has a little more resistance and position 1 has even more resistance since position 0 is just off (infinite resistance). When you have an old motor with worn brushes it may take more current to kick on. From what I've seen, max current position 4 is usually enough current to start the motor while the lower speeds cannot. My guess is they don't provide enough current to break the oxidation threshold. I would even venture to say that if people left it alone and didn't fix it, max speed position 4 will eventually stop working over time.