Interior heater blower on full power and won't stop

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the prince

Active Member
Joined
Sep 6, 2014
Messages
127
Location
Sheffield
Car
2001 CLK 230k
I used my Clk 208 for first time in 7 months today. Initially tried to use blower as windows misted slightly. No response when dial turned to 2,3,4,5 etc. After 5 minutes of driving the fan came on full power and despite altering the dial back to 4,3,2,1 off etc nothing happened. Even when the engine was turned off and the key taken out it continued to operate. So last resort took off blower panel and pulled out the blower power cable. Briefly attempted to reconnect the cable and started up on full power again so have disconnected again.

Any thoughts on what is wrong and the fix required.

Help very much appreciated.:confused:
 
By the way this car is new to me in that when i bought it 7 months ago, i parked it up for the winter, so i've done less than 5 miles in it. It did have the dreaded cabin water through blocked drains back in september, but i cleaned the drains and dried everything out. the heater did seem to work ok afterwards.

I've read through over 20 + threads about heater blowers and problems and seen mentioned about the Rest button causing the blower to operate for 20 minutes or so. I did press that in when attempting to start to heater when i wasn't operating. The query i'm trying to make is, is my system operating normally after having pressed the Rest button on then off again. I can't afford to leave the fan running on full whilst parked up or the battery will die soon enough. It's blowing like it want's to blow a house down, surely it shouldn't operate like this on rest or otherwise.

Help still needed and appreciated.
 
The heater fan regulator is a common issue. Less likely the HVAC control unit.

The fan should operate at about level 1 when you activate REST.

Did you find the fuse?
 
Thanks for advice. Not checked fuses. As the fan blower is operating i assume that the fan is working as normal (if a fuse had blown wouldn't it fail to operate), it must be whatever controls the fans speed and on/off is at fault. Is it the regulator / resistor that performs this job? If so i'm thinking that a new resistor is required like this:
Heater Blower Motor Fan Resistor for MERCEDES C E CLASS CLK SLK 2028207310 | eBay

Anyone else have an idea?
 
Another possibility is the contacts. I had a similar problem which was solved by removing the knob from the panel and squirting in some contact cleaner.
 
Another possibility is the contacts. I had a similar problem which was solved by removing the knob from the panel and squirting in some contact cleaner.

What is contact cleaner. Is that like WD40?
Ahh just looked on-line at this electrical contact cleaner spray. I'll give it a go. I think the next thing will be to change the resistor.
 
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Had a problem on my W202 where the blower would intermittently operate at full speed whatever setting the fan was on. Always stopped when the ignition was switched off though. I changed the resistor and the blower motor itself, to no avail. The fix was a replacement heater control panel, and even then it took the 2nd replacement to fix it (both were used). The fact your blower starts as soon as you connect the cable leads me to think you may also have a control panel issue. I remember the same thing happened on one of my repair attempts.

Your motor brushes are likely to be badly worn given the age of the car, so either new brushes (from eBay, etc.) or a new blower motor may be advisable too.

Good luck!
 
Thanks for advice. Not checked fuses. As the fan blower is operating i assume that the fan is working as normal (if a fuse had blown wouldn't it fail to operate), it must be whatever controls the fans speed and on/off is at fault.

I just mentioned the fuse if you wanted to pull it out to stop the motor. When the regulator ("resistor") fails, the heater blower may run at full speed even when ignition is turned off.
 
Had a problem on my W202 where the blower would intermittently operate at full speed whatever setting the fan was on. Always stopped when the ignition was switched off though. I changed the resistor and the blower motor itself, to no avail. The fix was a replacement heater control panel, and even then it took the 2nd replacement to fix it (both were used). The fact your blower starts as soon as you connect the cable leads me to think you may also have a control panel issue. I remember the same thing happened on one of my repair attempts.

Your motor brushes are likely to be badly worn given the age of the car, so either new brushes (from eBay, etc.) or a new blower motor may be advisable too.

Good luck!

Advice appreciated.
 
I just mentioned the fuse if you wanted to pull it out to stop the motor. When the regulator ("resistor") fails, the heater blower may run at full speed even when ignition is turned off.

I'll be totally honest i don't know where / which fuse the heater is located at.

I think i'm going to buy some electrical contact cleaner and give the control panel a clean out, but i'm definitely looking to buy a resistor and swap that. Any advice on whether the pattern parts i.e non-mercedes original resistors are ok. They are about £20 new on ebay, whereas the original second hand with no guarantee are about the same if not dearer.
 
I'll be totally honest i don't know where / which fuse the heater is located at.

I think i'm going to buy some electrical contact cleaner and give the control panel a clean out, but i'm definitely looking to buy a resistor and swap that. Any advice on whether the pattern parts i.e non-mercedes original resistors are ok. They are about £20 new on ebay, whereas the original second hand with no guarantee are about the same if not dearer.

I have a spare one (non-OEM) if you would like it. Purchased new in May 2013, was fitted for a few months - it made no difference to the problem I mentioned above, then when I replaced the control panel for the 2nd time I reverted to the OEM resistor, initially to see whether I still had an issue or not. As the problem was then fixed, I left the original resistor fitted.
Photos below - it looks 'as new' and AFAIK it works. Yours for £5 inc. P&P 2nd class. PM me if interested.
 

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Above part fitted. Did the job. Was in dealers yesterday and they agreed that the scuttle pan backing up water into the cab area is most common reason for these failing.
 

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