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George
George, BMW Technician
Category: BMW
Satisfied Customers: 1861
Experience:  BMW Master Technician over 20 years BMW Dealership Experience. BMW Auto Repair Shop Business Owner
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BMW 328i The blower motor on my wifes 97 e36 no longer operates,

Resolved Question:

The blower motor on my wife's '97 e36 no longer operates, and I think the problem is a bad ground wire at the final stage unit. I measured 10 ohms of resistance at the brown wire to a good ground. This doesn't make sense, right? Why would there be any resistance on this wire?

The blower motor itself works (I checked by connecting a small 12V battery across the appropriate wires at the final stage unit). Also, the climate controller does vary its voltage on the blue/red wire. And, there is the right voltage from the relay to green/brown wire. Finally, I did swap out the final stage unit (just to make sure).

What else should I check? Where does the ground wire on the final stage unit connect? Thanks.
Submitted: 3 years ago.
Category: BMW
Expert:  George replied 3 years ago.

George :

Can I have the last 7 digits of your VIN #

Customer :

Sure. Hold on a sec while I check.

George :

OK

Customer :

It's AV46647

George :

The ground goes back to the control panel and then from there it goes to a body ground, so you will need to disconnect the connector at the back of the control panel and re-check resistance. You are probally reading resistance from inside the control unit.

Customer :

Actually, the 10 ohms is what I measure at the connector (without the final stage unit in place) vs. another ground wire.

George :

What type of voltage do you have coming out of the final stage on pins # XXXXX & 5.

George :

You measured it at the connector of the control unit?

Customer :

I haven't checked voltage with the final stage unit in place. I've done all my diagnostic at the connector. At first, I thought it was a bad relay. But the voltages all checked out. It was only in measuring continuity that I found the resistance of the ground wire at the final stage unit connector.

George :

Ok I understand all this, but my question is when you measured resistance on the ground wire you had the final stage unplugged and you measured it at the final stage plug. Correct? If so did you have the connector on the back of the control panel unplugged while taking this measurement?

Customer :

OK. I finally understand your question. The climate control unit was plugged in when I made that resistance measurement. However, the wiring diagram doesn't show the brown wire from the final stage unit connecting to the climate controller. It should go to ground point 203, right? That ground point is also connected to a number of items in the interior, including the emergency flasher (which works okay).

George :

According to the BMW ETM it goes to pins # XXXXX & 23 of the control module connector X1527 and from there it then goes to the common ground connector X10012. Re-take the measurement with the connector unplugged from the back of the control unit and see what your reading is then. And then with everything back together see what voltage you have coming out of the final stage on pins # XXXXX & 5.

Customer :

Will do. Thanks. Based on what you've seen, what do you think is the issue? Wiring, final stage unit (replaced already) or control module?

George :

Has your control module shut itself on and off at times on it own?

Customer :

No. It seems to be okay. Without the blower motor working, I hear the A/C compressor turn on when I hit the AC button. When I make the fan speed go to zero, the ventilation doors close the way they should. Other than the blower motor, I have no reason to suspect the control module.

George :

OK this is the most common problem with this system the display panel will black out and come back on at times, since this is not happening the 2nd most common problem is the FSU, I have never seen any wiring problems but always a possibility. And last the blower motor itself.

George :

Is it an after market FSU?

Customer :

Thanks again, George. I'll recheck my diagnostics. I do know the blower motor works based on what I've done so far. The final stage unit I used is an OEM part from another 328i (owner was parting out and said it worked prior to removal).

George :

That is probally your problem then, is it all metal or does it have a black plastic end?

Customer :

The heat sink is all metal; epoxy at the end cap with the connector.

George :

Those are the bad FSU's don't even waste your time unplugging the control panel and checking the ground, just check the pins # XXXXX & 5 on the output to the blower and see if you have a varing voltage with different speed settings.

Customer :

Got it. Thanks. I'll accept so that you're paid.

George :

Click this link this is what the updated FSU should look like.

George, BMW Technician
Category: BMW
Satisfied Customers: 1861
Experience: BMW Master Technician over 20 years BMW Dealership Experience. BMW Auto Repair Shop Business Owner
George and 3 other BMW Specialists are ready to help you
Expert:  George replied 3 years ago.

Thank you very much,

George

Expert:  George replied 3 years ago.
Did you click on the link?
Expert:  George replied 3 years ago.

Thank you very much for the Bonus,

George

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