Root cause insight into the common BMW blower motor resistor failures

Actually, I was remiss in not stating that the blower motor generally fails by acting weirdly, often said to "have a mind of its own", and, most often by a parasitic current draw overnight that kills the battery.

i guess they call replacing a simple resistor with a bunch of transistors.... "progress"

i'd replace the module with a bunch of power resistors and maybe a PTC (self resetting) fuse

Mark

Mark

I don't know what a "TO-3" device is, but nobody removed anything in those photos other than the goop that covered the circuit board.

Focusing just on that Elmos Semiconductor AG IC from this thread:

It might be a generic or a special chip; I can't find it on the web:

That seems like an EXCELLENT idea, if we can put some kind of temperature indicator in the FSU tines, then we can observe what the temperature is in situ - which might tell us something about what is overheating these things (assuming heat is the culprit).

Just put your ammeter into the heater blower fuse connector and you get the current of the blower motor.

Are you sure it is not already a pulse width regulator? Those transistors look like they are TO-220 packages, not TO-3. PWM has been around longer than SMT parts.

Maybe it is transients from the motor that are causing the failures.

Another place you could measure the current is by putting an ammeter in place of the blower motor fuse.

tm

So the crafty germans are using a high tech solid state resistor instead of a PWM speed controller???

If I had one and it blew I think I'd be designing a PWM controller to take it's place. Need to find out what kind of signal the controller expects, but that shouldn't be too difficult.

That isn't necessarily the case. For example,t hey could be correctly designed, rated for the application, etc but have a manufacturing defect in just one of the components.

A better questions is why BMW apparently doesn't give a damn to do the failure analysis to find out what's wrong. I have a friend who has an X5 and had this problem with the blower resistors. Even worse, the only symptom was it was draining the battery and it took a huge number of hours to track it down.

While you're all wondering about that problem, might as well add the fancy aux radiator fan to the list. This car had that go and now the replacement one has failed again. And the symptom there is, again, it drains the battery even when the car is off. That fan is a real POS. Instead of just a simple fan motor, it's a fan that's variable speed, driven by a PWM signal. So, instead of just a motor, that fan sitting in front of the hot radiator has electronics in it. A real genius of a design. And for what? Like the fan can't just be on or off? Only reason I can think of is that they want to save a few watts of power to try to get better fuel economy. And for that their customers get to shell out $500 for a new fan every few years.

The dopes at BMW aren't any better at PWM's either. They use a PWM signal to control the aux fan on the radiator. You, know, the one that comes on if the cooling temp gets too high or the AC is on, etc. Apparently just a simple on/off motor wasn't good enough. So they made another one of their German electronic miracle gadgets that's part of the fan motor. That's right, electronics sitting right next to the hot radiator.....

On the TV show All in The Family, the meathead was arguing about Nixon and Watergate with Archie. Archie told the meathead that Nixon's mistake was when it involved electronics, ie bugging, taping, etc, that he should have used the Japanese, not Germans, ie Haldeman, Ehrlichman, etc. I think Archie was on to something.

I had a dodge caravan that fried its heater AC motor speed control resistor repeatedly....

the connector to the wiring harness detoriates from the high current and the voltage drop causes the connector to heat up and the entire assembly fails.

Oddly enough I repair roll laminators that apply plastic film to paper think menus:)

laminators experience similiar failures so I did the following.

Purchased a new resistor block, soldered wires on all the connectors putting a heavy wire on each one.... Put a pigtail on each one. Installed resistor block. Its screwerd to the fire wall.

Cut the plug assembly off the harness, stripped all wires, twisted them together and installed wire nuts on each one.

had the van for years with zero problems for this part:)

All the standard Elmos part numbers begin with an E.

My guess is that the number on the chip is 10901D and that the other two numbers are date and batch codes.

--scott

That's an interesting idea.

The fuse for the blower motor is called the "infamous F76" for a reason.

It's a 40 amp fuse under the glovebox but it's in a really inaccessible spot; however, it's right side up, so, the wires going INTO it are visible from the tips of your feet under the glove box.

So that's a possibility; but you'd have to cut the wires.

Hmm, it did look like it had quite a heat sink. I had assumed it used PWM to change speed, which should not generate much heat but my assumption might be wrong (or my understanding of PWM...) A solid state design that gets hot on purpose seems like a poor design to me.

On Thu, 21 Mar 2013 16:07:23 -0700 (PDT), Mark wrote in Re Re: Root cause insight into the common BMW blower motor resistor failures:

Why not just buy a Toyota and save yourself a lot of problems in the future.

If you google for 10901D it comes back with hits to Chinese chip brokers that show it as an Elmos 16 pin surface mount chip. Which is consistent with what's in the picture of the failed module, it has 16 pins. But I could not find any data sheet on the part either.

I found the same. The chip is listed here:

But there is no datasheet there.

I found a Russian language description of it here:

Here is a google translation

REGULATOR ELMOS 10901D Car Voltage Regulator Category: Car Source: Radioland country Electronics Temperature controller cabin air KAMAZ

Source: Plans radiokonstruktsy Simple Temperature compensated voltage regulator. Controller together with 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.

Source: For the life of a soldering iron ... Regulator for automotive windshield

Source: MASTER KIT The controller measures the wiper-this control is designed to use regular mode switch blades and is contactless.

Source: For the life of a soldering iron ... Temperature compensated voltage regulator device in some ways superior 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).

Source: For the life of a soldering iron ... Voltage regulator 2012.3702, 22.3702, 221.3702

Source: For the life of a soldering iron ... Voltage regulator 201.3702

Source: For the life of a soldering iron ... Voltage Regulator 13.3702

Source: For the life of a soldering iron ... Voltage regulator RR132A, 1112.3702

Googling for the Russian text, I find they appear to have the same problem with the same FSU over here: