Help, heater either hot or cold!! W203

[philiggy]

Hi all

havent been on here for ages.
Just bought a 2006 c200CDI

The heater is eithe red hot or cold....its terrible, cant find antthing on it and its making car unusable

Cheers
Phil

 

[bembo449]

hi phil , so its not pressurising the water system at all ?

 

[AMGeed]

Get your duo valve (heater control valve) checked.
I had similar symptoms and mine looked like this on removal

 

[philiggy]

Its all fine just had thermostat replaced,,,,where is duo valve situated?

 

[philiggy]

hi phil , so its not pressurising the water system at all ?

No I dont think so

 

[AMGeed]

Its all fine just had thermostat replaced,,,,where is duo valve situated?

Should be under the master cylinder on the drivers side bulkhead. The part isn't expensive £30 odd but its an awkward job to do.
BTW, this is only an opinion and please confirm with an indy/your garage before deciding to replace this valve.

 

[philiggy]

apparently mine doesnt have a duo valve!

 

[philiggy]

apparently mine doesnt have a duo valve!

Should be under the master cylinder on the drivers side bulkhead. The part isn't expensive £30 odd but its an awkward job to do.
BTW, this is only an opinion and please confirm with an indy/your garage before deciding to replace this valve.

Should be under the master cylinder on the drivers side bulkhead. The part isn't expensive £30 odd but its an awkward job to do.
BTW, this is only an opinion and please confirm with an indy/your garage before deciding to replace this valve.

 

[AMGeed]

OK.........I thought all W203's had them??

Oh well, back to the drawing board

 

[andy.alias]

Hi Philiggy, did you ever fix this?

 

[alexanderfoti]

Yes, no duovalve on the W203's. Heat/cooling is controlled by flaps.

You can try normalising the flaps by holding Windscreen defrost and recirc buttons until the lights flash.

 

[andy.alias]

Yes, no duovalve on the W203's. Heat/cooling is controlled by flaps.

You can try normalising the flaps by holding Windscreen defrost and recirc buttons until the lights flash.

Tried that, made no difference, I have read that it could be the sensor, but I’m not sure where it is, some say the roof light cluster and some say the controll dials..

 

[alexanderfoti]

Tried that, made no difference, I have read that it could be the sensor, but I’m not sure where it is, some say the roof light cluster and some say the controll dials..

You need to plug it into diagnostics and compare the values from both.

 

[Oldspanners]

Tried that, made no difference, I have read that it could be the sensor, but I’m not sure where it is, some say the roof light cluster and some say the controll dials..

Do you have any clicking noises coming from around the heater controls on switching the ignition on or off.
I had this problem and it turned out to be a heater flap control motor but can also be a cracked plastic operating arm.

 

[andy.alias]

Do you have any clicking noises coming from around the heater controls on switching the ignition on or off.
I had this problem and it turned out to be a heater flap control motor but can also be a cracked plastic operating arm.

No ticking noises, I might try a punt on a new light fitting, only a tenner on eBay.