A/C blower motor resistor problem
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Joined: Sep 2014
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From: Florida
2003 E500
A/C blower motor resistor problem
I have a 1997 C280. The blower motor resistor went out and I replaced it with one I bought online for about $40. When I plugged the resistor in, the fan motor started running immediately at a low rate of speed with the key off. I sent the resistor back and the new one they sent does the same thing.
The plug to the resistor has three wires, one outside wire is hot at 12 volts all the time (even with the key off), the other outside wire is a ground, and the third wire, which is the middle wire (white), shows around 2 volts when the key is off. When you crank the car and push the fan up a notch, the white wire voltage rises a couple of volts. Each successive fan speed that you go up, it rises in voltage until it hits around 12 volts at max speed.
What I need to know is this? Is the white middle wire on the plug to the resistor supposed to have constant low voltage even when the car is turned off? If not, then I am having an electrical problem prior to the plug. If it is supposed to have constant low voltage, then the "cheap" resistors I have bought must not be cutting off the low voltage like they are supposed to do and thereby allowing the voltage to reach the fan motor.
I appreciate any help any of you can give me. I am in Florida and I need my A/C back soon. I have to either put in or pull the fuse to the blower motor every time I crank or turn off my car... bummer.
The plug to the resistor has three wires, one outside wire is hot at 12 volts all the time (even with the key off), the other outside wire is a ground, and the third wire, which is the middle wire (white), shows around 2 volts when the key is off. When you crank the car and push the fan up a notch, the white wire voltage rises a couple of volts. Each successive fan speed that you go up, it rises in voltage until it hits around 12 volts at max speed.
What I need to know is this? Is the white middle wire on the plug to the resistor supposed to have constant low voltage even when the car is turned off? If not, then I am having an electrical problem prior to the plug. If it is supposed to have constant low voltage, then the "cheap" resistors I have bought must not be cutting off the low voltage like they are supposed to do and thereby allowing the voltage to reach the fan motor.
I appreciate any help any of you can give me. I am in Florida and I need my A/C back soon. I have to either put in or pull the fuse to the blower motor every time I crank or turn off my car... bummer.
Thread Starter
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From: Florida
2003 E500
Will do.
I am about to have an auto electrician take a look. He is good and should come up with an answer. I will let you know. Is your car also having a constant low voltage source to the white middle wire? I have been taking my fuse in and out for about three months now.
I will keep you informed.
I will keep you informed.
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clk 200
yea got to take my fuse out or the blower runs constantly, and i live in Norway so its getting a bit cold now to keep popping the hood to put the fuse in and out tried 2 resistors now off ebay it got better it was on full blast now just on low speed i seen a wiring diagram and it seems to go through a relay so maybe thats the problem im waiting for my guy at the garage to get back to me, im really at a loss with it and im hopless with car electrics, hope you get some good news, an origanal regulator here is around $600 
Thread Starter
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From: Florida
2003 E500
Nope. The electrician who works on my vehicles said he doesn't work on Mercedes. Go figure. So, I am installing two flip switches under the passenger side underpanel. I will let you know how they work out. It is 100 bucks just for the local shop to take a look at it. Maybe I'll have it fixed later, but I can't see sinking 4 or 500 dollars into it right now. If you find a solution, I would appreciate a shout. Good luck...
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Thread Starter
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From: Florida
2003 E500
Fixed?
So, you bought another relay yourself or did you have a mechanic buy it? Did you buy it online? I bought two online and neither has worked. I paid around $45 U.S. for each of them but some of them were priced over $100. I figured I just bought too cheap a resistor. I was about to buy an expensive one to see if it works. If you bought yours online, how much did you pay for it and do you have a link to the site you bought it from? Thanks.
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clk 200
fixed
Bought a new blower regulator off eBay around $50 but the problem was the same just the fan was on low instead of full blast, but my local mecahanic fixed the problem by adding a relay to the power that was feeding the blower when the engine was off and now it works as normal was only arounder $80, don't forget I live in Norway so it was around 600kr witch is really cheap, just ask you guy if he cam do it only took around 2hrs and it's perfect now works as it should without taking the fuse out all the time.
Thread Starter
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From: Florida
2003 E500
Photo
Is there any way you can post a photo of the relay and where he installed it? I would like to put one in myself if possible. Thanks in advance. I am glad yours is fixed. 
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clk 200
I will ask him tomorrow where he put the new relay if I can access it easy I will be more than happy to send you some pics, I'll ask my guy if he has a wiring diagram you can use and I'll try and send you that too. I'll call in there tomorrow hopefully we can get yours fixed too I know how annoying it can be.
Thread Starter
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From: Florida
2003 E500
Thanks
I really appreciate that. It has been a while for us, and I have probably taken that fuse in and out at least a hundred times. I appreciate your kindness and look forward to the information.
Jim
Jim
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clk 200
Hi Jim I have been to the garage today and he is not at work but he is back tomorrow I will try and take some pics tomorrow is a bit cold today -12 Celsius but it's warming up tomorrow so I'll get it done as fast as I can for you ok.
Thread Starter
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From: Florida
2003 E500
Fine
Of course it is okay to wait. Please don't put yourself out over this. It is 24 Celsius here today. We have very mild winters. It only gets down to 0 Celsius about two days a year. Stay warm...
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clk 200
There are the pics Jim hope they help he tried to explain what goes where but he lost me, I'm really not good with electrical things on cars, if there is anything else I can do just ask and I'll try my best for you,
Thread Starter
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From: Florida
2003 E500
Thanks so much
Lee, I am deciphering them now. I really appreciate your time and effort to get these on. I will let you know how I make out on this. It looks straightforward enough at first glance, but it will take a few minutes. Once again, thanks so much.
Jim
Jim
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clk 200
I'm sorry it's not much to go by my mecahanic didn't know so much when he was trying to explain he had an auto electrician to do it, but I hope you can figure it out from the pics if I can get hold of the electrician I'll ask him but I can't promise he isn't from round here, and where I live think alaska with less people lol. Let me know how you get on with it.
Thread Starter
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From: Florida
2003 E500
Lee, I can be reached at jimgibson7@hotmail.com. That way we don't have to extend this thread any longer than it is. I just purchased the relay on Ebay and it will be here in about a week. The pics are excellent, but there is only one thing I cannot see clearly. I see the relay hanging down and recognize all the wiring, but cannot see where the wires connected to the relay are going to or coming from. I assume the blue and red wires on the relay are going straight to the blower motor, but that is only a guess. I cannot tell where the gray and yellow/gray wires go that are connected to the relay. That will tell me where to put the relay in line in the circuit. I usually do all my own work and that is the last piece to the puzzle. If you will email me, I will tell you about where I live in Florida. We have one retirement community near here with over 100,000 in it alone. Thanks again for all the info...
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2008 E63 AMG
Blower motor works , but all by itself at times?
I have a 2008 E-63 AMG, I have read on the forums about the Blower and the resistor having problems. I have replaced both the blower and the resistor on the car and the symptoms are the same. When I first turn on the car, I can leave off he Climate control and suddenly the blower will go full, then lower itself and then shut off. When I turn on the AC its cool, and works fine, the blower however will stop , come on, and stay on even when car is turned off completely. Sometimes I can turn on the climate control and it works like it should, for about 10 minutes. And then the symptoms begin. I went to the "answer" web site and the mercedes expert there said, to reprogram the climate control module. Has anyone ever hear of this , or that particular fix? Going crazy.. Thanks for any help.
