Heater fan failure

[Treebster]

My heater fan has decided to stop working. When I first bought the car it worked intermitently but now it is completely non-functional.

I suspect it may be the switch because when it did work intermitently the switch had to be pushed pretty hard to get the fans working. Sometimes if you pushed the switch even though it would click the fans would not come on, until you pushed the switch a bit harder.

Heat is still coming from the vents, so the heater part still works.

So before I remove the dash and start playing with my volt meter, has anyone had any experience with this kind of fault? Is the switch knob prone to failure, or could it be something more sinister?

Car is a '97 400.

[mb450]

Have you seen this thread?

http://www.pistonheads.co.uk/gassing/topic.asp?t=5...

[over_the_hill]

Is it a three position knob or a push in and twiddle knob like mine.
I had a problem where the grub screw had come loose (on side of knob) so it was slipping on the spindle and wasn't always allowing the spindle to make a good "click".
It's very easy to remove the knob with an alan key then you can push the spindle (clicky bit) in and out properly. This will only take a few minutes to check.

[Treebster]

over_the_hill said:

Is it a three position knob or a push in and twiddle knob like mine.
I had a problem where the grub screw had come loose (on side of knob) so it was slipping on the spindle and wasn't always allowing the spindle to make a good "click".
It's very easy to remove the knob with an alan key then you can push the spindle (clicky bit) in and out properly. This will only take a few minutes to check.

It's the push and twiddle knob like yours. Can you remove it without taking the dash apart?

[over_the_hill]

The problem with mine was that the grub screw had come loose so the twiddle knob had slipped down the spindle.
The knob fits over the spindle but the spindle doesn't always fit tight into the hole in the knob
If the knob slips then the spindle doesn't always click properly because the knob hits the dash and stops it going in far enough.
Hope this comes out
This is the knob over the spindle with a gap between the knob and dash and a gap between the spindle and the end of the hole inside the knob.
The full stops represent gaps and the = are the spindle

____ ......I
I...========
____ ......I

if the knob slips you get the spindle tight into the hole and not enough gap between the knob and dash to allow the spindle to be pushed in enough.

____ I
I ========
____ I


This can be done without removing the dash. If the knob has slipped put a small bit of packing - tiny piece of card or similar into the knob hole to stop it slipping along too far.

Edited by over_the_hill on Thursday 15th October 18:23

[Zumbruk]

Also worth knowing is that there's an undocumented fuse for the heater fan motor. I drove mine for a while with it not working because I knew it was going to be a b*st*rd to replace the fan/motor, and when I finally bit the bullet and told the menders to go ahead and do it, they found a fuse...

Can't tell you where it is, though.