Root cause insight into the common BMW blower motor resistor failures

i don't know who you think you're talking to, but i have consistently advocated /not/ deconstructing this unit. it's not worth it when cost of replacement isn't that high or you can build an alternate controller that will be more reliable.

at least i can follow a thread without being a crotchety old fart.

i don't /want/ to reverse engineer it any more than i want to repair broken light bulbs. you were the one bragging about how easy it was. i said it wasn't. and when it comes down to walking the talk, you won't.

i guess we should be grateful...

Apparently I'm talking to a blowhard troll.

Ass. The first step in designing a replacement is to understand what it is supposed to do, and how the original performed that function.

Show us.

Send me some defective modules, or quit trolling.

This does not count the hazardous issue of the soldering failing, causing hazards to the users of the equipment :-(

That's why there are exemptions for the military and telecom industry, where it's actually important that stuff work properly.

What I find ironic is that the shorter lifespan of consumer gear caused by the RoHS manufacturing has actually increased the amount of electronics going into landfills, making worse the problem that it was intended to reduce.

--scott

Most of the people on the BMW forums think it's one of these.

Other people have suggested this also.

Some say the potting is what is causing the stress cracks.

Re-insert without potting, is the "said to be" solution.

One question: If the FSU works without potting, what was the purpose of the potting?

Good catch!

I will try this morning. (I was away on a trip for the past two days).

PS: Had to look up araldite:

The red jumper was a hack added by one user to fix the solder cracks, I think.

This implies two transistors (although I only found one).

I will dig through the mess again - but I think I was too fat thumbed when I cut it open, and may have destroyed the evidence.

I do have a second FSU (since two failed on me) though ... but I want to try to FIX that one (instead of destroying it).

I wasn't sure how to cross reference using that list. For example, it had only one BMW entry (camera module); and it did not have GKR or Sitronic or Valeo brands; nor the keywords FSU, nor FSR; but it did have things titled "blower motor controller), e.g.,

FORD F50F-19E624 heater blower motor controller ('97 L. CONNIE) 1

Regarding cost, it seems we can get aftermarket parts for about $100; and the part at the BMW dealership cost about $175.

Regarding repair, some have intimated that unpotting and resoldering is a solution.

If that's true, then that might be a viable "fix".

However, I must ask: If it works without potting, and especially if the potting is what's causing the problem, then what was the original purpose of the potting in the first place?

maybe it's similar, maybe it's not. the fact that each of the different unit manufacturers has different internals and that they've changed over time doesn't help you.

no???? really? are you /sure/ about that??? or doesn't sarcasm work for you???

no, you're doing that.

they're not my modules [again, you're not following the thread] and i wouldn't replace them - i'd pwm the motor instead.

dude, give up on that already. you'll never get good thermal contact second time around.

to keep the elements out. and the inquisitive.

and yet, some say that there can be increased reliability.

btw, if you want /real/ reliability, you wire wrap.

that's bogus. unless there's been a MAJOR screw-up, potting compounds are carefully matched to the thermal and chemical application - they serve to increase reliability, not degrade it.

I am aware of that. It looks like it ties the two collectors together. But does it go to the contact that connects to the fuse? The main point is "do the collectors (center pin on transistor) connect to the 12 volt input to the module"?

Thanks, tm