Blower Motor won't turn off on 2000 C280

[tracyc]

Hey guys,
Just realized that my blower motor won't turn off. I shut the car off; it still runs. Turn the climate control off; it still runs. The "REST" is not on as well; it still runs.
For now I just pulled the fuse. For grins, I plugged the fuse back in after 30min and the blower started back up (with no key in the ignition). Had anyone experience
this problem and know how to correct it? Thanks for reading.

[wichipong]

you might have a short in the fan clutch... it happened to me..

[vaspen]

was it hot out ? fans will continue to run sometimes after motor shut off its to get the air flowing while the motor sits
remember a motor sitting after running will get hotter than when you were driving it because the radiator isn't getting as much air flow
I would wait for 30-45 min depending on how old ur battery is and see if it goes out if not then maby a bad relay, fan clutch, fuse, fan temp sensor

[tracyc]

I let my car sit overnight and plugged the blower fuse back in and the blower started right back up with car off. Could this be a bad relay (also known as a multipupose relay)? I unplugged all the relays one by one behind the fuse box but the blower kept on blowing, it never turned off! So, I'm not sure where to go from here and any help you can give will very helpful.

[tracyc]

So, I'm thinking it's either the relay or the blower motor resistor. Your thoughts before I got out and buy. I don't want to just through parts at this.
Thanks!

[imautoparts]

When you say blower motor are you referring to the one under the dash? If yes, I'd say your climate control control head (where the buttons are) is malfunctioning. Do a cold reset on the whole car by pulling the positive battery cable - with the CAN computerized controls in these cars a cold reset can work wonders. If that doesn't fix it you can get a used unit cheap on car-part.com (they rarely fail so there are tons of them available). It is an easy component to remove and reinstall.

Don't forget that after you reconnect the battery you'll have to cycle all your windows full up and full down, and your sunroof has to be pushed in the up vent position till you hear a soft click. Until you do that none of the auto-open circuits will work.

I figure you're talking about the AC/heat blower, so I pulled the car-part listings for the control heads. Sorry they don't line up neatly on cut and paste:

1997
Heater/AC Control
Mercedes C Class C280 2.8L AT COMPLETE ASSM 000356 $30 Best Price Auto Salvage USA-OK(Oklahoma-City) E-mail 405-632-7888
1996
Heater/AC Control
Mercedes C Class 202 Type, (C220, C250D, C280 & C36),A/C 2173 $29 Used Salvaged Auto Parts USA-KY(Georgetown) E-mail 1-502-857-0585
1997
Heater/AC Control
Mercedes C Class Black 878 $29 Used Salvaged Auto Parts USA-KY(Georgetown) E-mail 1-502-857-0585
1997
Heater/AC Control
Mercedes C Class C280: Auto A/C-0MI 13F011 $25 G & N Auto Recycling L.L.C. USA-TX(El-Paso) Request_Quote 915-877-5353 Request_Insurance_Quote

1999
Heater/AC Control
Mercedes C Class C280: Auto A/C-86K A 13F036 $25 G & N Auto Recycling L.L.C. USA-TX(El-Paso) Request_Quote 915-877-5353 Request_Insurance_Quote

1996
Heater/AC Control
Mercedes C Class 202 Type, (C220, C250D, C280 & C36),A/C-147K A A78585 $25 JFK Auto Salvage USA-TN(Murfreesboro) Request_Quote 615-624-7262 Request_Insurance_Quote

[tracyc]

Well, I unplugged the positive on the battery and reconnected to reset the controls. My heater blower still turns on by its self even in the off position. I replaced the blower motor resistor only with the same results. I'm completely baffled now. Anything else I could possible check? Could it be a relay? The climate control counsel its self? I hate to have to keep dumping money into this but it's my everyday car and need to get this fixed before the cold weather starts. At this point; I don't care if your idea is out of the box, I just need options to look at. I'm some what knowledgeable of my car but not on everything. So, technical description will help, I think. Thanks everyone!

[imautoparts]

If I were you I'd replace the dash control unit itself. I've heard they are not hard to remove and replace, but you might want to post it as a separate thread and see if anyone who has done it before can give you the various steps.

If they are easy to access I'd say unplug your existing one first and see if that stops the motor. If so, you've found the problem.

[tracyc]

Thanks for the input "imautoparts". I removed the dash control unit itself and unplugged the unit completely. Once again my heater/ac blower kept running even when the car is off.
So, this is what I have done so far (when the car is off):
1. replaced the blower regulator - blower kept running.
2. Reset the controls by unplugging the battery - blower kept running.
3. Unplugged the dash control unit - blower kept running.

I'm talking out of the box here:
Could there be bad resistor in the fuse box? Not sure if anything behind the fuse box would control the blower beside the fuse.
Is there a wire location that can be check from the fuse box to the regulator? I'm just fishing now.
Thanks to everyone who replied and who could give other options to check.
Tracy

[imautoparts]

Wow Tracy, that is a bizarre and difficult problem. I am absolutely at a loss as to what to suggest next. If the control head is unplugged and the blower is still running, typically one would think of a short circuit of some kind.

So anyway I did a very broad-based google search of "heater fan, won't turn off OR keeps running, Mercedes" and found a bunch of similar threads on a wide variety of models. Apparently this is a common fault on the computer controlled Mercedes of this era.

On several of them people mentioned that it was always the blower regulator, but that they had to try a couple of times before they got a good one. In one case a guy had to exchange his twice before the problem was resolved.

Here is the search I used - all of the threads I looked at said the regulator behind the glovebox is definitely the problem.

https://www.google.com/search?q=heater+fan+won't+turn+off%2C+mercedes&oq=heater+fan+won't+turn+off#bav=on.2,or.r_cp.r_qf .&fp=6de4259520f5374d&q=heater+fan%2C+won't+turn+off+OR+keeps+running%2C +mercedes&safe=off

John H

Oh and PS: These don't fail often enough to be afraid of one from a junkyard. That's the route I'd take if you can't exchange the one you've already replaced.

[tracyc]

Thanks imautoparts,
I'll order another blower regulator but I need to know if it's normal that the blower would continue to run when the dash control unit is completely unplugged? If it does, then maybe I bought a faulty regulator.
One other question, I did replace the blower unit itself 2 months ago and reinstall my original regulator to the new blower. It worked fine until last month when I came across my current ploblem of not shutting off.
Here is my question: Is there different model numbers for my 2000 C280 blower/regulator but the parts appear to look the same? Could it be that I order the wrong part number for my blower or my new regulator?
In the mean time, I'll find another regulator and see if I get the same problem.
Thanks!

[imautoparts]

I always ask the dealer first to give me the exact part number based on my VIN number. Ever since they went real-time on their parts systems Mercedes is notorious for making minor changes - dozens of minor changes, right in the middle of a model year.

My faith in the system has been shaken lately by the failure of the dealer to locate my power seat comfort relay. The parts manual says my car has one, the seats won't operate without one, and yet the dealership has been completely unable to locate the relay on the car. I'm thinking of calling a couple of large dealerships and tell them mine couldn't help and suggested I call them. It's frustrating when you simply cannot find the problem part - that's one reason I so feel for you with this problem.

[tracyc]

Well, I installed a new blower regulator and got the same results. Maybe it's time to take this into the dealer. I know I'll get sock with a hefty bill but I'm out of options...I think.

[imautoparts]

Tracy my heart is with you on this. What a situation.

[tracyc]

Well, before I break down and send my car to the stealership, I thought I would give this one more shot. I took photos of my diagnosis. Maybe this will help determine the root cause.
First off; let me recap my issue. My interior blower motor continues to blow when the my car is off (no key in the ignition). My "REST" is off as well. The only way to turn off the blower is to pull the fuse or unplug the regulator.
Today, I tried to find where each of the 3 wires that connect to the regulator and blower (both which are new) goes to and see if they are not damaged which may have cause a short.

I traced the white wire with a peach stripe back to the climate control unit harness.
[PIC 873]
Next I traced the Red wire with a Blue stripe back to the fuse box. It went to my No.29 (30amp) Fuse.
[PIC 875, 877, 878 & 879]
Here is look at the underneath of the fuse box. Not sure where the large Red wire goes to. I'm assuming from some power supply like the battery.
[PIC 876]
Finally, I traced the Brown wire (Ground?) to a location in the engine compartment but I'm not sure if it's the correct one since there are several brown wires grouped together.
[PIC 880]
This is what I found out where the wires go to I believe. If I'm incorrect, please let me know. I also want to state that for grins, I cut the brown wire at the regulator plug and the blower stopped. I did splice it back together.
Ok, after a few hours tinkering with car, I'm sitting here going through my options. The only things I maybe considering are 1. I may need a new climate control unit 2. The ground is faulty 3. The climate control unit harness went bad.
If I'm way off about my diagnosis, let me know. I hope with these photos help & someone can help me and point me in the right direction. If you need more information let me know. Thanks for reading/viewing this post! My next reply will have the rest of the pics.
Tracy

[tracyc]

Here are the rest of the pictures.

[tracyc]

bump

[tracyc]

Today, I installed a different climate control unit with same results. So, I currently replaced the blower, regulator & climate control unit. The blower still turns on when I plug in the regulator. Does the red wire from the 3 pronge regulator harness go directly to the fuse box or does go to something else before the fuse box? I'm trying to trace whre the 3 wires go to so I can check for a possible short. I know the white w/pink stripe goes to the climate control unit harness. The brow goes the engine compartment somewhere. Any help will be greatly appreciated!

[imautoparts]

Tracy, if it was my car I'd install a discreetly hidden switch to cut off that brown wire when you need to, or better yet determine if it is a 12V power source or a ground, and put in a relay that cuts the circuit on and off when the key is turned. That way you can move on to less frustrating issues and still have a fully functional car.

As I search for and locate more and more electrically related forum posts around the world on the W202, I've decided that the electrical system is 'the' issue with this model (that and chassis rust) that may prevent these cars from being long-term keepers. It's a darn shame because the engine and transmission system, the climate control mechanical bits and other auxiliary parts seem to last and last and last; but none of that matters if you are at a drive-through and the damn window won't roll down, or if some other minor fault that is just unacceptable in a luxury car.

I wonder if the small electrical harnesses that control minor systems are beginning to degrade like the ill-fated early engine harnesses? It would be interesting to learn if Mercedes used the same biodegradable 'green' insulation on all the wires in the car, but only upgraded the underhood bits when they started deteriorating quickly due to heat. It could be that all of us are sitting on a time-bomb of cracking and dissolving insulation for less critical systems.

[MauiMerc]

Tracy, did you ever find the problem with the nonstop blower? I'm having the exact same problem with my 99 C280. I couldn't get mine to turn on at all so I changed the regulator, now I can't get it to turn off!

[NW_Merc]

Tracy, did you ever find the problem with the nonstop blower? I'm having the exact same problem with my 99 C280. I couldn't get mine to turn on at all so I changed the regulator, now I can't get it to turn off! The resistor situated on the fan motor is at fault. You need to take the fan out and change this. It should fix the issue.