The heating switch on my aging (09) 500 is getting really stiff to turn.

Does anyone know whether it is just the plastic switch itself, of whether it's further behind.

It it worth spraying it liberally with WD40 (or something similar), or even taking the HVAC controls off, and trying to clean the switch? Is it worth doing that?

I don't know whether anything (e.g. coffee) has been spilled on it previously, as I've just got the car from my daughter (lucky me).

It needs a few jobs, including a new timing belt kit, but that's another story.

It’s worth taking the panel off and turning it on it’s own and maybe cleaning it but it’s more likely to be the mechanism behind. Don’t use WD40 though.

The panel just prises off. Get a trim removal tool or a wide flat bladed screwdriver with plenty of tape on it and it will prise off. You have to pull pretty hard if it’s not been off before. Once you can get the tips of your fingers behind it, just yank firmly.

If it's one of the dials (manual heating controls) then the dial is connected via a mini bowden cable to the heater valve.

The cable has a knob on the end. If this is coming adrift of the dial housing then that might cause stiffness - you'll only know by removing the dial.

The cable never gets wet, so can't be rusty.. but it's clamped in place here and there with a clip that has a channel for the cable to pass under it. If a clip(s) has rotated slightly with the cable's natural movement, it might be pinching the cable.

The heater valve is most likely (I never see the 500 one) a simple hatch that rotates over a hole and "seals" the hot water circuit via an O-ring. When you have it apart, you can disconnect the cable and operate the hatch by hand. It will likely be very easy to move (they tend to leak rather than ever wear out...) but if yours is stiff and you can't see anything else, then that could also be the culprit.

My bet is the cable though.


Ralf S.

Hmm, sounds complicated.

I know the control fascia can be tricky to get off, and I'm loathed to do it for fear of breaking something. However, every time I twist the hot/cold control knob, I think I'm going to break it.

In view of the fact it is actually working, and it's the middle of winter, I might wait a few months until there's better weather and lighter nights.

I must admit, I was hoping to cure it by liberally spraying it with WD40, but I'll heed typecastboy's warning.

Thanks for your replies.