Root cause insight into the common BMW blower motor resistor failures

Actually, it's the same transistor, which broke in half while I was attempting to get the black rubber eraser stuff off of it to read the numbers.

It's really going to be HARD to read those numbers now...

Yes.

This quote below is verbatim from this location:

- the FSU works again

- there is no PWM , the gates signals are continuous voltage only , this is the reason why it heat so much its aluminium box... In fact there is no point on the board where square signals are present. Can somebody check its own FSU if it's the same ?

- the 2 bridges are in fact 2 resistors 10 milliohm used to balance the currents between the 2 MOSFET and balance the power also. The mesure of the DC voltage on those resistors can be used to evaluate the current of the blower and its worn state.

- I guess the principal duty of the computer on the other side is switching off the power transistors if the control voltage goes under 1V.

I put the FSU back in the car and it still work, I don't know if it will last long. because of the heat...

Olivier[/QUOTE]

I only found 1 transistor.

This is what is suggested in this quote below:

Ok, they are most likely transistors and the two straps are combining the emitters. Is the center junction of the two straps connected to the motor?

Does the red jumper connect to the 40 amp fuse? If both of those are a yes, then they are most likely NPN power transistors and the jumper ties the collectors together. Or power darlingtons. And it is just a linear supply.

In your other pictures, the spring clips just hold the transistors against the heat sink.

I think he is incorrectly calling the SMT IC a mosfet.

What went in the other three holes on the PC board? What was under the two spring clips on the heat sink?

t,

You said you tested the FSU alone. If so, how can you say there is no PWM signal between the car and FSU?

the gates signals are continuous voltage only , this is the reason why it heat so much its aluminium box... In fact there is no point on the board where square signals are present. Can somebody check its own FSU if it's the same ?

urrents between the 2 MOSFET and balance the power also. The mesure of the DC voltage on those resistors can be used to evaluate the current of the bl ower and its worn state.

Say what? 10 milliohms is .01 ohms. How could that possibly balance the power to a motor in a 40 amp circuit?

ng off the power transistors if the control voltage goes under 1V.

Which makes no sense at all.

last long. because of the heat...

It seems they last at least a few years. Maybe it's like gas. You buy it and you go so far. I think you're in way over your head here;

ent,

no

V.

..

s,

The main points of his post, like the "two bridges that are .01 ohm resistors, that "balance" the motor don't concern you in the least?

Blind leading the blind

Sadly, I speak from experience, in both respects.

nate

I 'think' (but I'm not sure) that these are the resistors in series:

I'm still trying to figure out if there was only one or two:

irly

If they are resistors, I've never seen any that look like that. Also, given that you want to thermally bond any components that generate major heat, why are they not heat sinked? With any power design I've seen, the key components, eg the transistors are directly bonded to the heat sink.

The main points of his post, like the "two bridges that are .01 ohm resistors, that "balance" the motor don't concern you in the least?

Blind leading the blind =============================================

It is common to place low value resistors in the emitters to balance the current in two paralleled devices.

As to blind, you exhibit that trait much better than anyone else involved with this thread. Asshole.

/You said you tested the FSU alone. If so, how can you /say there is no PWM signal between the car and FSU?

/ the gates signals are continuous voltage only , this is the reason /why it heat so much its aluminium box... In fact there is no point on /the board where square signals are present. Can somebody check its own /FSU if it's the same ?

/Say what? 10 milliohms is .01 ohms. How could that /possibly balance the power to a motor in a 40 amp circuit?

Not to the motor idiot. To the transistors.

/Which makes no sense at all.

Certainly not to you.

/It seems they last at least a few years. Maybe it's like /gas. You buy it and you go so far. I think you're in way /over your head here;

But not yours?

You can increase the sensitivity by winding multiple turns around the clamp on core.

Two turns makes it a 400 amp meter and so on.

I was never crazy about that style of heatsink.

fairly

You've never seen strips of nichrome in a space heater?

Two.

Actually that looks good and should work just fine.

That type of probe is self contained, meaning it does not depend on the DMM input impedance for proper match.

BUt 80 Amps is kind of small I think, I have a AC/DC clamp that does 800 amps, but to do low current readings of less than 1 amp becomes a problem with AC. DC I can zero it.

Jamie

Be careful with so called information from those types of sites. Most of their information is badly translated, or just plain wrong. Tabao.com is a prime example of crap information. I have never found correct information there. Most is from chinese Ebay sellers who make things up about items they sell. They have no idea what it is, just that they can sell it on Ebay or Tabao.com.

thyristor-transistor electronic ignition unit with a long spark, ensuring the rapid start-ups at various operating conditions, allowed to increase battery life of up to nine years.

switch blades and is contactless.

designs. The controller can be used as a universal device is suitable not only for mounting on any car, but everywhere, where the generator rotor speed is variable (eg, wind power). Choose the appropriate control elements, it can be easily adapted to work with any voltage (up to 400V) and excitation current (tens of amperes).