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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53942
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Marty. Earl here. I have a 1998 E320 with the old style

Customer Question

Hi Marty. Earl here. I have a 1998 E320 with the old style blower regulator. The hosing around the motor broke (otherwise it still works) and ordered the new style blower/regulator. The new one does not work. If I plug in the old one and hold the motor mount together, it works fine. I put the new motor on the bench and hooked to 12 volts. The motor spins fine. I tested continuity of the wiring harness, and all is in order. That left me with a resisitor/regulator issue. I got the parts supplier to send me a new one. I bolted it together, but it will not run. Any ideas?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi Earl, I've had problems with the aftermarket blower regulators. Have you already tried a second new regulator? If you haven't I would do that first. It sounds like you just got a defective blower regulator.

Customer: replied 1 year ago.
If you read my question, the regulator that came with the motor has already been replaced.
Expert:  Marty replied 1 year ago.

I did read your question but it was not clear to me that you replaced the regulator twice. Turn the key on and turn the blower control to high and see if you have voltage on the white/pink wire. Let me know what you have.

Customer: replied 1 year ago.
There is power from each of the 3 contacts at the car connector, to the ground on the connector. I hooked up the old motor again, and holding the broken housing together, it runs on all variable speeds.
Expert:  Marty replied 1 year ago.

Are you saying that the old motor works when plugged into the new regulator but the new motor will not?

Customer: replied 1 year ago.
No. the old motor is the original style MB blower/regulator. It will not work with the new style regulator. What I am saying is that if i take the old broken motor/old regulator, and hold the broken housing together, it works fine, at all speeds. The new Blower is good, I hooked it directly to the battery and it runs. I have tested the harness, and there is continuity on each of the leads. The first new style regulator came with the motor. Since I had run all of the diagnostics, it appeared that the first new regulator was bad. The supplier sent a new one. Hooked up, the new blower, with either of the new regulators, still does does not work.
Expert:  Marty replied 1 year ago.

Ok, unless the wiring is incorrect the problem is with the regulators. Order a Behr brand regulator and you should be fine. If you want to send me a picture of how everything is connected I'll take a look at it.

Expert:  Marty replied 1 year ago.

Hi Earl, I'm just following up with you on the Mercedes. Did you get this figured out yet? Have you ordered another regulator?

Customer: replied 1 year ago.
I did. It does not work either. I went to a pull and pay and removed a blower motor and regulator from a wrecked E320 and plugged it in, It works fine. Problem solved. $11.00.
Expert:  Marty replied 1 year ago.

Glad you got it squared away. Obviously the problem was with the regulator or the wiring.

Customer: replied 1 year ago.
Idk. If it was the wiring, the used fan and regulator would not have worked. My guess us 3 bad news regulators.
Expert:  Marty replied 1 year ago.

Very possibly. I was referring to the wiring between the regulator and the blower motor not the wiring to the regulator from the car. Glad you got it sorted out. If you would please take a moment to rate my service on this question I would appreciate it. If you do not rate my service I do not get paid for helping you.


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