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Discussion Starter · #1 ·
So, I recently had my blower motor stop working on my E350. I checked the fuse up front and it looked good. (That feeds the dash unit (10 AMP?) I checked the rear, and it was good, but it was supposed to be a lower amp fuse, but it had a 40A installed? But both were good.

I pulled the motor and gave it a spin and it started working. So, I reinstalled and ordered a new motor.

A day or so later (still waiting for the fan) it quit again.

Motor came in. I replaced it. (Had the wrong connector so I had to splice in the old connector.) Long story short, it didn't work. Old motor is very stiff, though.

I suspect the old motor may have burned out a fuse in the prefuse block (F32) and I'm going to check it out tonight. I think someone may have kept this motor turning by putting a bigger fuse in the rear block 40A!!. That may have allowed things to get out of hand.

That said, I want to make sure there's not a resistor or some other component I need to check, as well.

Does anyone have a schematic of this circuit I can look at so I don't go down a rabbit hole?

Thanks,

Tim
 

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There has been recently reports where brand new Behr motors has been crap from box. You having initially a wrong connector may have part of the issue here, but I don't know if control is still the same on both models.
 

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You do not mention model year nevertheless, motor is controlled by a regulator (resistor) common to replace both the fan and the regulator together. The regulator gets a message from the AC control module on what speed to run the fan so you also need to check that you have voltage on the signal line How to Test a Mercedes Benz Fan Blower Motor Regulator
 

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Discussion Starter · #4 ·
There has been recently reports where brand new Behr motors has been crap from box. You having initially a wrong connector may have part of the issue here, but I don't know if control is still the same on both models.
Thanks! I'll definitely check this out. I could be missing something, but I don't seem to have any power at the connector where the motor plugs in to the regulator.

The motors seem to be identical, with only two wires leading from the motor. Pelican advertized it as the OEM manufacturer, but failed to flag the difference in the connector. Still, I'm going to put power on the motor to verify its functionality.
 

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Discussion Starter · #5 ·
So I continue to be at a loss. I have a voltage supply to the resistor. The motor turns with 12V. The signal line from the Control unit has a variable voltage based on fan control, but I get no voltage out of the resistor. So I ordered a new resistor. Same thing. I ordered a replacement. Same thing. Behr Mahle replacements, both. To be more accurate, I'm getting .886V.

So I broke down and stopped at the dealership and bought the OEM resistor ($350) and it appears to be the same thing.

To be clear, I have voltage into the regulator/resistor. I have a 0-12V signal from the controller. I have .886V at the motor out of the resistor connector.

I'm at a loss.. and its hot outside.
 

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All due repect the $ you spent on parts could have easily paid for an independent to perform a quicktest using MB diagnositics more than likely providing definitive diagnose. Anyway, try checking connector/pin @ AC control module.
 

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Discussion Starter · #8 ·
Hindsight is 20/20. and I haven't been able to find an independent..

That said, I have power to the regulator/resistor, I have a variable voltage signal from the head unit (as I turn up the fan control, voltage goes from 0 to 12V) , and the fan works with direct voltage to it.

The voltage output of the regulator, as I plug in the car with voltage and fan voltage signal starts at 13 volts and then momentarily drops to .886 volts with no load on the output. When a motor is attached it stays at zero. At the input I maintain 14+ volts at the supply but the signal voltage drops a bit from the 13V input to 10V.

Anyone with a schematic, let me know.
 

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Discussion Starter · #9 ·
You do not mention model year nevertheless, motor is controlled by a regulator (resistor) common to replace both the fan and the regulator together. The regulator gets a message from the AC control module on what speed to run the fan so you also need to check that you have voltage on the signal line How to Test a Mercedes Benz Fan Blower Motor Regulator
I have a 2011 E350 Bluetec.

I have signal from the head unit but not voltage from the regulator. I'm on my third regulator, so I'm not sure if there's something else I'm missing. My only thought is the connector itself but I'm getting continuity throughout and maintaining voltage in the line, although the signal line drops a couple volts when its plugged into the regulator.
 

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You might still have wrong type of regulator, have you checked EPC? I just read couple of similar cases in our national forum, one case was wrong type of regulator, others were just unexplained non-run problems. Couple of those were actually 'Nissens' brand blowers, one Behr. Only thing that helped was change brand of blower. In all cases motor run ok when put voltage on table. But in car it might spin a seconds if plugged to car plug when control was on. If control was off, it didn't even try. Another was motor spin 30 second but if controls were touched, it died immediately.

So ensure regulator is right one, then get an another brand of motor of refurb your old.
 

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Discussion Starter · #11 ·
You might still have wrong type of regulator, have you checked EPC? I just read couple of similar cases in our national forum, one case was wrong type of regulator, others were just unexplained non-run problems. Couple of those were actually 'Nissens' brand blowers, one Behr. Only thing that helped was change brand of blower. In all cases motor run ok when put voltage on table. But in car it might spin a seconds if plugged to car plug when control was on. If control was off, it didn't even try. Another was motor spin 30 second but if controls were touched, it died immediately.

So ensure regulator is right one, then get an another brand of motor of refurb your old.
Thanks for this. Can you give me a link to the national posts you refer to?

I had changed my blower, initially, as I had measured the power TO the regulator, mistakenly. I'm going to jumper in the original blower and see if it makes a difference.. although that would be exactly what I did originally.

The regulator, all (4) of them, including the OEM model that I took out, have the same output. It gives me full voltage out for about a second, and then goest to .886V. Even if I jumper the power and signal together (so the signal is full voltage) I get the full voltage for a fraction of a second and then .886. I'm assuming I can't get (3) bad regulators, but the output is baffling.

Makes me wonder if I have insufficient current (only voltage) from the main power supply under the dash, although I see no sudden drop when I plug the power in.
 

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Discussion Starter · #12 ·
As far as the regulator, the original Behr number has a different suffix (12 instead of 10) on all three replacement regulators, one OEM. All parts reference the original Mercedes OEM part number. Parts department at the Dealer said there were no variations that year on my car.
 

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Discussion Starter · #14 ·
As far as the regulator, the original Behr number has a different suffix (12 instead of 10) on all three replacement regulators, one OEM. All parts reference the original Mercedes OEM part number. Parts department at the Dealer said there were no variations that year on my car.
So.. a post Mortem:

I had given up and booked an appointment at the dealership. Other than the cost of buying OEM parts, I've always been pretty happy with the desk at Coppus Motors in Tiffin, Ohio. It's a practical group of guys who've always been pretty straight shooters.

To recap, I had ordered an OEM, non-Mercedes branded fan when I measured a voltage coming from the regulator/resistor. Plugged it and got nothing, even though I had voltage to the regulator and a voltage signal from the controller. The motor I had taken off, though, was very hard to turn.

I ordered a Regulator and the motor still did not turn, and I had no voltage from the regulator output. Called for a replacement and another was sent out on a new order as I needed it quick. The new one arrived, same thing.

I was getting voltage for a few milliseconds, though.. and it would drop. So in prep to have the dealership work on it, I put the old motor back in and it worked.. with the old regulator..

My conclusions:

1. The old motor was good.
2. The Mercedes branded motor has a higher current requirement.
3. The regulator/resistor has a safety circuit to check for current draw to keep from burning itself out. (this explains the 10 milliseconds of voltage before it kicks off when I apply power and signal to the unit with no load, or the replacement motor attached.
4. The old regulator/resistor is tired and is either intermittent or fails at higher temperatures.
5. I'm keeping one of the Mahle/Behr regulator/resistors and replacing the old one.. as it is likely the cause of the original failure.

It's been running fine since.

Going to return the new "OEM" motor that apparently spins TOO freely.. Returning the Genuine branded Mercedes regulator. Still in the bag.
 
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