1993 mercedes 190e 2.3 heater problem
 

I have a 1993 190e 2.3. The heat will only work when it warms up over 12 celcius(50f) outside. The blower and temp gauge works as do all of the control buttons.
I have flushed the system many times and it seemed to help a bit.
This included a steam flush through the heater core.
Sometimes I get heat out the top vents but not the floor vents,just cool air.
This is basically erratic and I never know when I will get heat.
I will say though that it works perfectly well when warm outside.
No mechanic seems to know why unless they do a expensive exploratory. Help. Freezing in Vancouver

Have you changed the thermostat? It should have been done when you had the coolant system flushed. If it wasn't, that's the first place I'd look.

Jeff Pierce

Hi Jeff;
Sorry for taking so long to reply. We tried the thermostat to no avail. We just did an exploratory and checked the heater valve,inside temperature gizmo and after three hours labour cost they figured it was the potenzio meter in the dash. This they say will take 8 hours of labour to remove dash and replace unit.So a 1200 dollar plus tab. I may as well buy a fur coat.Anyway to get to the potenzio meter without removing dash?
Otherwise I will get a portable heater to get through Winter!
This car is a pain to maintain! It only has 138,ooo kilomteres also!
Thanks
Roberto

I have an older 190e (85) don't know if this will help but I had a similar problem. take out the glove box liner and to the right near the vent is a small motor with a blower. it sucks air through a hose that leads to a port above the rear view mirror. This is where it gets air to sense the indoor temperature and how to adjust. Mine was siezed, replaced it cheap and no more problem

If you need to replace the potenzio meter in the dash, you can access it through the instrument cluster opening or by removing the center dash vent.

Haasman