CLK 200 heater issues.

[paolo]

Hope this is in the right section.
I have problems with the heater on the above car, (2005 model). Heater seems to be on full all the time. I have reset it with this:
"Switch on ignition.

Press recirculated air and defrost buttons on control panel together for longer than 5 seconds.

The LED's in the defrost and recirculated air buttons flash alternately.

Wait until the LED's stop flashing (approx 30 sec) system set to defrost LED on.

Switch off ignition.

After 40 sec re start engine."

Seemed to work, coldish air blowing out, but as soon as i turned the heat up full, then down again, it carried on blowing out hot air.
I have seen several videos highlighting the heater duolvalve that may need cleaning / replacing, but cannot find any reference as to where it is in my car.
Any help would be most welcome.

 

[dry run]

Had similar odd behaviour where only one side would turn down and the other sides wasn't very cold. Took it to my local ATS Euromaster for a check and re-gas Their machine checks and disgnoses what is wrong. an hour later and just £50 poorer, I had a fully functioning heating/cooling system. Might be worth giving your local ATS a call?

 

[Oldspanners]

Any strange clicking sounds from the dash? That's a known problem with HVAC stepper motors and or arms breaking.

 

[mattkh]

Seemed to work, coldish air blowing out, but as soon as i turned the heat up full, then down again, it carried on blowing out hot air.

Any help would be most welcome.

You wanted COLD air in the car, so why did you turn the heat up..?

 

[paolo]

"You wanted COLD air in the car, so why did you turn the heat up..?"
Quite simple, as i said, after the reset it was pumping out cold air, so obviously the only to see if the fix had worked was to turn the temp up and down!

 

[mattkh]

"You wanted COLD air in the car, so why did you turn the heat up..?"
Quite simple, as i said, after the reset it was pumping out cold air, so obviously the only to see if the fix had worked was to turn the temp up and down!

This has reminded me what my domestic heating engineer once told me. He said the thermostats are very sensitive things, so change them gradually.
What happens if you turn the dial up a little bit at a time...?

 

[mioba]

When was your AC last re- gassed.
I find about every 7 years keeps it optimal.

 

[Rory]

Assuming it's the same as C Class, there isn't a duo-valve. Temperature is controlled by air-blending flaps.

Issue could be flap/flaps sticking (is it the same on both sides?) or a controller issue. Poss one of the interior temperature sensors has failed.

 

[paolo]

Hi Rory, where are the flaps and sensors?

 

[Rory]

On C Class flaps are in the dash and there are two temp sensors, one in the heater control panel and the other in the overhead console.

 

[paolo]

Thanks Rory, doesn't sound like a DIY job then.