Please Help - Unusual Merc problems

[Chambo]

My 1996 C class Mercedes has a number of unusual random problems and my mechanic has never seen it before.

Basically on purely randon occassions the heating will come on full and cannot be turned off (ie if turn on aircond and/or turn off the fan the heating and fan still continues flat out)

The other random problem is the speedo stops and the 3 brake warning lights come on all at once (despite no known mechanical issues and the brakes are fine)

Both these problems occur purely randomly and of course did not occur in front of the mechanic. My mechanic could not find any problems.

Can anyone help point me in the right direction?
Does anyone have any ideas what the problem could be?
Help please.

 

[Francois]

I am not sure how this works on a 1996 C class, but I had more or less the same symptoms and the following was the cause:

1. Duovalve was broken/stuck. This would cause permanent or intermittend hot air to enter the cabin.

2. Speedo would die and certain functions on the steering column would top working. This was due to some fuses that weren't sitting properly in their holders.

Hope this helps...

 

[Chambo]

Thanks for the note and advice - I looked into the issues you raised but unfortunately it did not solve my problems.

My first problem is losing control of the fan, once that happens the fan blows flat (even if switched off) out at the temperature last set - any ideas anyone as to causes?

In relation to the second problem being speed and warning lights, I have checked all the fuses and no issues there. Any more ideas anyone on possible causes of these problems?