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Discussion Starter #1
Hi,
My blower fan is sometimes intermittent. So I decided to measure the voltages, coming from the blower motor resistor, on different fan speeds. I got:
Speed 1: 8v
Speed 2: 12v
Speed 3: 16V
Speed 4: 20V
Speed 5: 22V
All the voltages are close approximates. I have an analogue multi-meter, so it's not as precise.

I also cleaned the contacts on the motor itself and tried to oil it. Lastly, I checked that 200amp fuse thing that's under the hood, and near the big fuse box... (it's the little black one with some very thick wires going in and out of it). This fuse looks fine, as far as I can tell.

So, my questions are.... am I getting the right voltages off of the resistor? If the problem continues, what's my next step?

P.S. The climate control is manual.

Thank you all!
 

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All the voltages are close approximates. I have an analogue multi-meter, so it's not as precise.
I am surprised at these results, as you only have 12 volts available for control. Are you sure that you are on the right range with your multimeter, and that you are actually measuring volts?

I have some voltages from the WIS that I think are relevant to your a/c system.

Blower regulator A32n1 input from blower switch.

Stage 1 = 1.1 to 1.8 v
Stage 2 = 2.0 to 2.4 v
Stage 3 = 3.0 to 3.4 v
Stage 4 = 3.6 to 4.2 v
Stage 5 = 5.0 to 6.0 v
 

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Discussion Starter #3
Just an update... so far, the fan hasn't cut out. Perhaps it was an issue of corrosion. Tomorrow I'll see how it is on the commute to work. If there are issues, i'll post back.
 

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Discussion Starter #6
I haven't had a chance to re-check the voltages, but the same problem has been continuing.
When the problem occurs, turning off EC, changing the blower speed or setting recirculate do nothing... the blower still stays off until it feels like coming back on (which could be 30 seconds or so).

So what do I look at now?

Thanks
 

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There is a Blower Motor regulator module that controls the speeds. I believe it's a variable resistor. Your's is probably done. The fan motor should be ok since you say it blows at different speeds. Mine has been acting the same way but it always gets demoted by something else in my budget. :D

You can find the Behr(OEM) one for about 100 bucks online and maybe cheaper knockoffs/aftermarket on ebay.
 

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Discussion Starter #8
There is a Blower Motor regulator module that controls the speeds. I believe it's a variable resistor. Your's is probably done. The fan motor should be ok since you say it blows at different speeds. Mine has been acting the same way but it always gets demoted by something else in my budget. :D

You can find the Behr(OEM) one for about 100 bucks online and maybe cheaper knockoffs/aftermarket on ebay.
Thanks for your response! But how do I know that it's the resister and not the climate control unit? (it's the manual knob one)
I thought resistors either work or don't work, rather than sometimes work and sometimes don't work?
 

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had similar problems, thought it was my blower or resistor or combination of both. Replaced both with Behr originals, and now it doesn't work at all. I suspect it's the control switch. I measured the 3 wires going to the resistor, one is 12v, other is ground, and middle is control, but I'm not getting a reading from it :(
 

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Thanks for your response! But how do I know that it's the resister and not the climate control unit? (it's the manual knob one)
I thought resistors either work or don't work, rather than sometimes work and sometimes don't work?
You can either buy from a place where you can return it. So if it doesn't fix your problem you get your money or most of your money back and try something else. :D

Or measure again with the right scale on your voltmeneter and make sure your voltages are in the ranges spec'ed above in keyhole's post. If they are then it's something else.
 

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had similar problems, thought it was my blower or resistor or combination of both. Replaced both with Behr originals, and now it doesn't work at all. I suspect it's the control switch. I measured the 3 wires going to the resistor, one is 12v, other is ground, and middle is control, but I'm not getting a reading from it :(
I am not 100% on how it works but my guess is that it's a voltage divider setup in the regulator. You should be getting a voltage between 0-12V in the control pin depending on the resitor values. If you get nothing, it is probable you got a bad regulator as it implies the resistor is open thus no voltage.

Did you try supplying voltage to the blower by other means to make sure your blower was not bad?
 

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I measured pin 2 going to the blower resistor and got inconsistent values of 0v and 7v; turning the blower switch between off to full didn't change the voltage at all. I tried shaking the wire thinking there was a short somewhere, but the values didn't change at all.. I'm thinking my climate control unit (or at least the blower control) is busted... I'll try removing it in the coming days to test the output to the blower resister.
 

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Well today I had to drive the Benz and I banged on the climate control unit (manual type) and it started working normally, lol. So yeah, something wrong with it, hopefully I can replace the rheo inside
 

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please let us know how it goes. I think my climate control unit is also messed up.

As it seems to act up with different pressure/pushed to the knobs . I have the manual control unit too.
 
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