W107 Heater motor running continuously

[DaveBarnes]

Hi there, hoping someone can help me out here.

I have recently purchased a 1979 350SL (W107) and it's got a few problems!

The problem I currently need help with is that the interior fan, heater motor, runs continuously. Sometimes. Well, most of the time actually...

Occasionaly, it works fine and the fan speed control changes the speed of the fan as it should and you can turn it off completely. But most of the time it just runs at full speed and blasts me with air.

I've been told that it may be the motor or the resistor. I'm not sure what the resistor does with respect to the fan or indeed, where it is located or what it looks like.

I'm not sure if this is related, but there are a couple of ceramic blocks with wires connected to them, about 5cm long by about 2cm wide & high that are bolted to the inside of the front NS wing in the engine bay. One of these is a bit crumbly (technical term) and I suspect that it might need replaced. Not sure if these are the resistors though, but I'll probably have to replace them anyway when I find out what they are.


Any help would be greatly appriciated.

thanks
Dave

 

[Aussie Nick]

Ha ha . I love your honesty in the technical diagnosis. I dont know about this older model but the w202 has a similar (non crumbly regulator) inboard near the fan. In your model it may have been located in the engine compartment.It sounds to me that this is your problem and what you have observed is the regulator playing up. I am sure that another member will provide a second opinion on this very shortly. Regards

 

[television]

The heater on yours uses resistors, the resistors would not cause the problem it must be I think in the switching

 

[DaveBarnes]

thanks

Thans Guys

The crumbly bits are the regulators for the ignition circuit, so i'd better replace them before I go any distance, or we all know what will happen there.

Still looking into the fan though. The switch looks ok when I check it, but if it's not too expensive i might just get one and give it a try - might try e-bay first.

cheers
Dave