W209 heater not getting very hot

[JB052]

Noticed recently that the heater on my 2006 W209 280 is not getting very hot. The car runs at a steady 80 degrees C on the gauge although it doesn't seem to get to operating temperature very quickly. The air-con appears to work, there are no obvious clicking noises from the stepper motor linkages and I have carried out a HVAC 'system reset' using defrost and recirculation buttons which hasn't made any difference.

The only other point of note is that the cooling system was flushed a few months ago.

So any thoughts on how I can get the heater to generate something more than luke warm air?

 

[whitenemesis]

Maybe air-locked? Try bleeding the system.

 

[Gbrowncls55]

given slow warm up perhaps an open thermostat

 

[JB052]

given slow warm up perhaps an open thermostat

Is thermostat operation usually visible on the gauge, so is it possible to see the temperature climb past normal operating temperature, then drop back to normal?

 

[JB052]

Maybe air-locked? Try bleeding the system.

I did wonder about an air lock in the system, but not sure if specialist equipment (vacuum pump etc) is required. I'm unable to locate any bleed valves.

 

[Gbrowncls55]

Is thermostat operation usually visible on the gauge, so is it possible to see the temperature climb past normal operating temperature, then drop back to normal?

If the thermostat is stuck open then, in cooler weather, warm up can be slow, particularly on shorter journeys, this will result in lower heat from the heating system. Its only one possibility for your symptoms there are many others. As already stated, an airlock in the heating part of the system if not bled properly could very well be responsible.

 

[JB052]

As an update in case anyone is having similar issues.
Apparently it was the auxiliary water pump which had failed. Cost to interrogate the issue and replace the pump was £350 from a local Mercedes specialist.

 

[whitenemesis]

Glad you got it sorted
And thanks for taking the trouble to post the fix, very useful for others who may have a similar problem
(Not many do.. )

 

[Jigglyjohnson]

Had a few stats sticking and they can put the eml light on i would take the stat out and test and replace with a genuine stat