Why not much power from cabin heater?

[DegsBenz]

Not much power coming from my heater. Car is CLK 200K, W209, year 2006.
Settings go from 0 to 6 on circular dial, in half step increments. I closed off all vents except central dashboard, turned direction dial to dashboard, ran the car for a good length of time. Also turned AUTO heating off.

Thing is, I get no power really coming through until I hit 3 1/2 -> 4 on the dial. I only hear it also at this stage. Any suggestions to why this is so? Should I expect a dribble of heat coming out of heater until I turn dial well past half way?


Is it common on W209/Mercs in general of this age (2006) to have poor heaters? Banging my head against a wall with this one..

 

[ItalianTuneUp]

Is the coolant temp shown on the dash very low? If the thermostat is working then temp should rise fairly quickly to about 80/90C on a run.

I had a stuck open thermostat and I had no/feeble heating too. The coolant struggled to get above 50/60C too. Replacement thermostat fixed it and the heating returned.

 

[ItalianTuneUp]

Alternatively, maybe your heater blower motor has some issues if it's an issue of the fan output power, and not the heat output.

 

[grumpyoldgit]

As above, is the temperature gauge reaching at least 80º? If not your thermostat needs replacing.

Presume you are turning both left and right temperature controls up to the highest settings.
What do you have the recirculating air button set to?

In the cold weather, I set my (C Class) to Auto / L&R temp controls up to max / A/C off - button light on / Fresh air drawn in / Air distribution at 3 o'clock position. As the engine warms up the fans increase to full power, but are on a very low speed until it start getting warm. As the cabin reaches temperature the fans then reduce in speed.

Using Manual settings 3.5 - 4.0 is the same as mine, can't hear the fans until then.
Have you tried resetting the heater flaps? Should be 'how to' instructions on here if you search for it. (Sorry I can't remember which buttons you need to press to initiate it).

Edit: Found the resetting heater flaps instructions - This is for C Class but may be the same for CLK models - http://www.mbclub.co.uk/forums/1520581-post2.html

Failed thermostats seem to be a common problem.

 

[Rory]

Not much power coming from my heater. Car is CLK 200K, W209, year 2006.
Settings go from 0 to 6 on circular dial, in half step increments. I closed off all vents except central dashboard, turned direction dial to dashboard, ran the car for a good length of time. Also turned AUTO heating off.

Thing is, I get no power really coming through until I hit 3 1/2 -> 4 on the dial. I only hear it also at this stage.

I would say mine is the same. I keep meaning to look how the dash-top central vent is supposed to work as moving the wheel doesn't seem to do anything.

If you select face-level vents, does the air come through OK?

I find on long jouneys I can't use auto as so little air comes through the car. I set the air direction in the middle - up/down/face - and need the fan on 3.5 to be able to feel anything.

 

[Ted]

Cabin filter.

 

[ItalianTuneUp]

Anecdotally, it seems a few W209s suffer this issue...is it a common problem with this model?

 

[ItalianTuneUp]

And recirculation of air seems to hinder the elimination of moisture in the cabin.

 

[whitenemesis]

Check the condition of the cabin filter. Clogged and wet will reduce airflow to near zero.

Does it improve on RECIRC?

 

[After Shock]

My E Class (W211) seems to be slow to "warm up" too.................

 

[Rory]

And recirculation of air seems to hinder the elimination of moisture in the cabin.

As you'd expect.

 

[ItalianTuneUp]

As you'd expect.

Indeed, as the moisture can't escape outside.