2000 Ml430: Heater Always On - Benzworld.org

Georgeous · 11-10-2007, 06:34 PM

Hello,
I recently purchased a 2000 ml430 with 80,000 miles on it. It seems to be by and large in good working order except for the heating. I don't know why but it always seems to be on. Even if I turn the fan all the way down if I put my hand over the vent I can still feel a little bit of warmth emanating from it. When I put the fan intensity to 2, the heating is overwhelming. Temperature intensity doesn't seem to have an effect on anything.

What should I check next?

-George

mlfun · 11-10-2007, 08:04 PM

There is another knob selecting temp on the side. Is it missing ?
>>>>>No
Sorry I overlooked your last statement about "temperature intensity".

mlfun · 11-10-2007, 09:47 PM

If you found the temp knob, does the airflow change as you turn it from hot to cold and vice versa ?

43sqd · 11-11-2007, 01:59 AM

Quote:

Originally Posted by mlfun

If you found the temp knob, does the airflow change as you turn it from hot to cold and vice versa ?

I agree with mlfun. Does the temp. change? Is the heat coming out of the center vent only? Give a little more info.

CAHEK · 11-11-2007, 03:41 AM

make sure to turn off both temperature and fan dials and it will stop blowing hot air.

DelJ · 11-11-2007, 07:52 AM

Such strange answers! One should always be able to have ambient temperature air blowing into the cabin.

Obviously, something is wrong with the climate controls.

DelJ

Quote:

Originally Posted by CAHEK

make sure to turn off both temperature and fan dials and it will stop blowing hot air.

DelJ · 11-11-2007, 07:55 AM

The heater is always "on" in the ML430 as far as the heat exchanger is concerned; the system works by opening or shutting the heater vent. It appears that your heater vent controller is stuck open.

And yes, that heater does get quite warm when fully open!

DelJ

Quote:

Originally Posted by Georgeous

Hello,
I recently purchased a 2000 ml430 with 80,000 miles on it. It seems to be by and large in good working order except for the heating. I don't know why but it always seems to be on. Even if I turn the fan all the way down if I put my hand over the vent I can still feel a little bit of warmth emanating from it. When I put the fan intensity to 2, the heating is overwhelming. Temperature intensity doesn't seem to have an effect on anything.

What should I check next?

-George

CAHEK · 11-11-2007, 09:07 AM

Quote:

Originally Posted by DelJ

Such strange answers! One should always be able to have ambient temperature air blowing into the cabin.

Obviously, something is wrong with the climate controls.

DelJ

i agree that hot air blowing in your face is pretty strange especially when you just turned it off, but this workaround does the trick.

mlfun · 11-11-2007, 11:10 AM

Quote:

Originally Posted by DelJ

The heater is always "on" in the ML430 as far as the heat exchanger is concerned; the system works by opening or shutting the heater vent. It appears that your heater vent controller is stuck open.
...
DelJ

Sounds like it.
But if you are lucky, only the temp sensor is busted.

Georgeous · 11-11-2007, 01:02 PM

So after further observation, changing the position of where the air is blowing doesn't seem to have an effect on heat intensity. If turning the air temperature knob all the way into the blue I do perceive a slight reduction in heat but it is still definitely heating the cabin. So for this reason I believe it might be the heat valve slightly but not completely working.

So, where is this valve, could someone please put up some pictures or point me to a diagram please?

-George