Root cause insight into the common BMW blower motor resistor failures

Might be a good idea! :)

My E46 hedgehog cooked itself twice in 4 years!

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Reply to
carson ridder
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They haven't sold the Supra here in ages :(

nate

Reply to
Nate Nagel

If it's just a typical DC motor with two leads, apply 12V and it should run full speed. You could also measure how many amps it draws when running. That is, IF it's just an ordinary motor.

Reply to
trader4

Why would you have to cut the wires???? Simply remove the fuse and connect the ammeter. You guys make your lives so difficult

Reply to
clare

It's kind of amazing the fuse is 40 amps, no? I mean a 1 hp motor draws ~1500W And this heater blower is 480W? Seems like a lot to me.....

Reply to
trader4

But anyone who thinks they are somebody or something needs to own at least ONE weiner wagon - mabee two or 3 - one of each major brand - MB, BMW, and Audi - and perhaps a Porsche - just to prove they are not invulnerable and all powerfull. Either one of them can take a guy down a notch pretty quickly.

Reply to
clare

Not unless you want to become addicted and need to drive kraut burners for the rest of your life. I and several friends have unfortunately fallen prey to this disease and our wallets have suffered as a result.

nate

Reply to
Nate Nagel

Have you got a link to these "common problems" you keep posting about?

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Reply to
R. Mark Clayton

In message , " snipped-for-privacy@optonline.net" writes

If by PWM you mean pulse width modulation, then it would allow for variable speed, but a DC motor is an inductive load and is not sensibly controlled by such a system unless there is something in the circuit to allow the peak voltage generated by the motor at pulse cut of to be shunted to earth.

Reply to
Clive

That "something" could be as simple as a diode. PWM is commonly used to vary the power to a motor. BMW, for example, uses it on the aux fan motor of the X5. And I would suspect that it's also used for the blower motor because you wind up wasting a lot less power that way. And every little bit of power saved adds up and effects MPG.

Reply to
trader4

!- Hide quoted text -

I don't have a link, but we had the blower resistor widget go on an X5 here. And the aux cooling fan motor has gone twice. There are plenty of threads online about many people having those problems. Oh, and don't forget the nice X5 feature where the cable that they use to hold up the windows snaps, sending the window crashing down inside the door, breaking it into a million pieces. Had that happen twice too, once while the car was just sitting in the driveway. Other time was driving down the highway.

Then there are their defective rubber parts. Like the boot on the intake manifold that cracks in just a few years. Or the CV joint boots. I've had lots of cars with CV boots and only on the X5 do they fail every 20K miles. I've seen Honda CRVs that went 200K miles with no failure.

Reply to
trader4

In message , " snipped-for-privacy@optonline.net" writes

I agree with all you say.

Reply to
Clive

In message , Bimmer Owner writes

Motors are not just a resistive load though.

Reply to
Clive

PWM is the most common method of controlling the speed of DC motors - a flywheel diode is part of the "system" to handle the inductive kick-back. Virtually all battery operated variable speed power tools use PWM. So do virtually all electric bicycles with brush motors and the vast majority of electric forklifts.

In fact, just about any application of a brush type DC motor that requires reasonable speed control has switched to PWM control of some sort over the last 20 years, including power wheel chairs (except those using 3 phase brushless motors)

Reply to
clare

Take a blown fuse and use it for a test connector with a cheap

50-0-50A meter. Then you can just plug it in in place of the fuse to make the test. You won't even have to worry about the polarity. You can use a high current shunt, & a digital meter if you want more accuracy.
Reply to
Michael A. Terrell

It should generate less heat at low speeds, if it is PWM.

Reply to
Michael A. Terrell

Or just get the special tester that is made to plug into the fuseblock. Autel makes the MX101 and 201 (10 amp and 20 amp) units for the lighter duty stuff.

Reply to
clare

I've seen 20W power resistors in TO-220 packages.

Reply to
Michael A. Terrell

Is that cheaper than roll your own?

Reply to
Michael A. Terrell

It does indeed look like a TO-220 from the pin spacing (since there are no actual transistors in the photos, just spots from which they were removed).

But if it had been a PWM device, there would have been some filtering in there, inductors and capacitors to keep the noise from getting into the power lines. Designing clean and quiet PWM controllers is not quite as trivial as some folks have made it out to be.

This is possible, if it is the transistors that are failing. I don't see any big protection diodes in there either.

If it's a RoHS soldering issue, though, I would not be surprised.

--scott

Reply to
Scott Dorsey

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