1992,300D,2.5T Heater U/S? - PeachParts Mercedes-Benz Forum

perpetualroll · #1 10-05-2009, 11:26 PM

The heater does not work under the following conditions:
No blown fuses in the box,engine is running,sufficient engine coolant at 82C,selector temperature 75F,fan is running but no heat issues from vents.
What is wrong?Any advice will be appreciated.

compress ignite · #2 10-06-2009, 04:00 AM

1.Monovalve (Although when they go "Bad", It's usually "Wide Open Hot")
[German engineers design to guarantee defrost if all else fails...]
(It's in the front portion of the Battery Compartment...Follow the Hoses.)
I'd unplug the monovalve and see if it'll default to HEAT.
2.Auxiliary Electric Water Pump.(Under the Windshield Washer Tank)
'With the engine running and HEAT on can you FEEL the Auxiliary WP running?
3.CCU (Climate Control Unit).[Behind the Pushbuttons in the dash/console]
Be prepared to either:
a.'Go spelunking in the ReCycle yards for one.
b.'Turn over your retirement to the stealer.
4.Clogged Heater Core.
(take the Star, offa the hood and look for another Mercedes to drive underneath it.)
A "DeOiling" and Citric Acid Flush MIGHT offer some relief if it's #4.

Sev · #3 10-06-2009, 04:39 AM

Quote:

Originally Posted by compress ignite

1.Monovalve (Although when they go "Bad", It's usually "Wide Open Hot")
[German engineers design to guarantee defrost if all else fails...]
(It's in the front portion of the Battery Compartment...Follow the Hoses.)
2.Auxiliary Electric Water Pump.(Under the Windshield Washer Tank)
3.CCU (Climate Control Unit).[Behind the Pushbuttons in the dash/console]
Be prepared to either:
a.'Go spelunking in the ReCycle yards for one.
b.'Turn over your retirement to the stealer.
4.Clogged Heater Core.
(take the Star, offa the hood and look for another Mercedes to drive underneath it.)
A "DeOiling" and Citric Acid Flush MIGHT offer some relief if it's #4.

good info. what if i have the same problem, except that no heat is issuing ONLY from the center vents?

pmari · #4 10-06-2009, 07:00 AM

Quote:

Originally Posted by Sev

good info. what if i have the same problem, except that no heat is issuing ONLY from the center vents?

Hmmm? That's like ordering at a restaurant, your buddy say's;"I'll have a cheeseburger".Then you say "I'll have the same thing, But...without the cheese"

The answer to your question IS.....http://www.peachparts.com/shopforum/showthread.php?t=35373&highlight=center+vent

babymog · #5 10-06-2009, 10:49 AM

The center vents in the 124 are cool air only, either unheated outside air or A/C cooled air.

If they are blowing during heating, then you have a vacuum-pod issue or possibly just a vacuum issue, back to the previous post's link. The system is supposed to automatically close the center vents when heating.

Oldwolf · #6 10-06-2009, 11:09 AM

When you push the defrost button does the fan go to full speed and air only is routed through the top defrost vents?

Oldwolf · #7 10-06-2009, 11:14 AM

Also, this page will be useful to you.