Ive just bought an old 300D and there is a problem with the heating system..
when the car is varm, only HOT air is coming out of the fans. A friend told
me to change the heatpump, but that didnt solve the problem
Can anyone help me on what the problem can be? its really a problem, course
its really getting pretty hot inside the cabin hehe thu i live in cold
denmark, thats still a little too much
thx in advance
The heater control valve, called the "mono valve" needs to be repaired.
It can be rebuilt with a kit.
The cabin gets full heat (default mode) when the mono valve fails.
The mono valve is located between the car's engine and the firewall
(below the windshield).
My '87 300td does not have a "monovalve" and it's possible that the OPs 300D
also lacks one. There is a similar valve, contolled by the Climate Control
circuit, but it is not structured the same as a monovalve and is not
hmm to start with, it only blow really hot air out occaitionally, sometimes
first when i have been driving for 2 hours. i could often "fix" the problem
by setting the fan speed to max for 30 sek. then cold air came back. Now i
cant "fix" it anymore, as soon the engine is varm, it blows hot air out. So
that can not be the live feed then right? as I wrote a few post ago, I got
my friend to change a thing I call a "hot pump" and still the same problem..
I was trying to find a picture of that thing we replaced, but cant really
this one came
closest, but its still not the one. The one we replaced got 2 metallic
finally i found a picture of the device we replaced
and still i have the hot air problem. I will check the fuse and live feed
tomorrow, but sence the problem at first, only showed up accasionally, it
might not be that. Can anyone think of something else that could be the
Thx for the help btw :-) and merry christmas
The device in the picture looks to me to be the auxiliary water pump. It
runs only within a certain temperature range inside the heater to boost
water flow to the heater core. This is NOT THE PROBLEM.
You need to check (and probably replace) the heater control valve that
must be located very close to the auxiliary water pump.
") is the mono valve. But
the picture mentioned below is the water pump, which cannot be the
problem. So which one did you actually replace?
If it looks like the mono valve but kind of double it, that is still the
mono valve. Some cars have separate driver/passenger control. The
first picture shows the single control.
Check the connection at the valve controlling waterflow to the heater, it's
near the battery. If it is not a monovalve (and maybe if it is), the valve
will be normally open when the engine is running. An electric current closes
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