Blowe Motor Won't Quit/climate Control Problem

[dobbes]

I have a 2000 CLK 430. The blower motor for the climate control will not turn off. With the climate control set to OFF the motor will not turn itself off, just continues to blow through the defrost vents. Even when the car is off, the blower motor continues to blow. I had to take the fuse out to make it quit. Does anyone know what the problem is and how much they payed to have it fixed. Any suggestions would be greatly appreciated.

Thanks,
Don

 

[marnix]

Hi,
It looks like the points on the relay are welded together.
It should tell you in the manual wich relay it is

 

[jberks]

I will probably be the blower regulator - very common fault. There is no relay on them, just a sealed metal box near the fan. Its not repairable so a dealer only part and replace job. I did mine a year or so ago - easy job (on the 210 anyway) and the part was £125.
cheers,
JB

 

[marnix]

Are you saying that the fan is running straight from the battery?
Then why would it run with the engine switched off? Does the air con not go through the ignition?
I tought that the regulator was adjusting the speed of the fan depending on the temperature inside the vehicule, but you still need a relay to switch it on or off
Must check this on my car, as if there is no relay (or contactor) to switch the fan on and off it must be a fire hazard

 

[jberks]

I can't be certain about the relay as I haven't looked at the wiring diagram, however,not all circuits are controlled by a relay, they are simply fused to avoid major shorts causing a problem. In any case A relay is there, not to protect from faults/shorts, but to allow a low current circuit to control a higher one, Otherwise a lot of switches on the dash would need to be very heavy duty indeed.
In answer, no the aircon does not go through the ignition - for example you can use the auxiliary heater without a key being present. The regulator controls the fan speed based on a lower current supplied from the switch - supplied by the climate unit or fan switch. I would not be surprised if this is on a constant live. When the reg goes haywire it can cause anything to happen from the fan not coming on - to the speed varying wildly to just not going off - as in this case.

Anyway, a jammed relay would not cause the symptoms described. it wouldn't explain why "With the climate control set to OFF the motor will not turn itself off" as even if the power was supposed to go off and didn't, the switch feed would still go off with the fan switch and the reg would shut down anyway. The only things that can make that happen is either a faulty climate control computer, or a faulty regulator. The regulators are a known very common weak spot so its by far the most likely explanation.

 

[marnix]

Hi Dobbes,
When you turn the temperature up or down on the climate control, does the speed of the fan varies?
If it does there is nothing wrong with the regulator, if it doesn't JBerks may be right in his assesment.

 

[jberks]

Marnix - sorry but I have to disagree - the regulator can do absolutely anything - including behaving perfectly normally during normal use but refusing to shut down when the signal current is disconnected. I have heard of them refusing to start, stop or in the case of mine, the speed would vary wildly as you drove along. They can also whistle just like a failed fan bearing.

Anyway, its quite easy to test.
Just locate the regulator (not sure where it is in the CLK, possibly under the bonnet in the fan housing, on the W210 its under the passenger footwell kick panel). There will be 3 wires in and 2 out (to the fan). Of the 3 in, one is +ve feed, one -ve and one switch feed with a range of something like 0-7v (can't remember what I got on the meter) depending on the switch position. Turn off the aircon and the switch feed should drop to 0v. If the fan continues to run, the regulator is feeding it when the control signal is telling it to shut down and you need a new regulator. If the signal remains above 0 with the climate off then there is a switching problem.