Heater on full

[hoj]

Hi all,
just bought myself (today)a 1995 C250 Diesel and was driving home and discovered that the heater is permanently belching out hot air and cannot be controlled by either of the temp dials. The fan works ok though. Feel a bit fed up as the chap who sold it said everyhing worked perfectly, I didnt think to check the cool operation of the system. Can anyone please help................

 

[The German Flower Pot]

thats a weird thing

is it a manual dial system or a digital electronically controlled system?

could be a small fuse somewhere

 

[dave.robbo]

If you got it from a garage, take it back tomorrow!

If not, I'd imagine that the heater dials control cables may have come loose? (Assuming they ARE cable operated!)

 

[hoj]

its a manual dial system and got the car private. The guy who owned it had it 3 years ( wifes car ) its a dual wheel type system so not sure if its cable operated

 

[dave.robbo]

Hmm, as soon as I posted that I wondered about the cable thing.. Mine certainley don't feel as if they're cable operated.
Fuse certainley sounds possible.. I don't have a Haynes manual for mine yet, so can't look for you.

Do you have an indie near you you could ask? Whereabouts are you?

 

[Dec]

The cabin temperature is controlled independently for driver and passenger sides of the car by the two thumb wheels. The two thumb wheels control 2 duo-valves located close to the brake fluid tank, the have one water hose going into them and 2 water hoses coming out the other side going to the heater (one for driver side and one for passenger side)

When car is up to normal working temperature, turn both thumb wheels to cold (blue) try tapping the duo-valves gently with the handle of a screwdriver, this might free them if one or both are stuck open, remember it will take several minutes for the air to change from hot to cold when the thumb wheel is turned to cold.


Dec

 

[hoj]

many thanks for the advice Dec and Dave, will give it a bash tomorrow and will let ya know

Hoj

 

[The German Flower Pot]

do they look like this

 

[star]

do they look like this

Is that a special fitment "cat".

 

[jibcl500]

Is that a special fitment "cat".

Danny

I see youve got some pussy at last.

jib

 

[hoj]

Thanks for the picks to the German flower pot, they do indeed look similar to that but without the temp numbers on the thumb wheels, just blue, white and red. Have found the two valves in question and gonna give them a little persuasion with a light tapping instrument, namely a mark 1 hammer. Wish me luck !

 

[bigasotonuk]

Hi,
Another common problem with these is the heater control panel itself, so do bear this in mind.
Replacement units quite commonly seen on e-bay.

 

[The German Flower Pot]

Danny

I see youve got some pussy at last.

jib

thats woody (ginger kens brother)

 

[toxic]

i will second the duo valves

this link is for a 140 may be of some use

http://v12uberalles.com/Rear_AC_System.htm

 

[Dec]

That’s a go one toxic, there is also this one which will be a bit more familiar for the OP... http://forums.mercedesclub.org.uk/showthread.php?t=25909 that is if it is the duo-valves that are the cause of the fault.

Dec

 

[Parrot of Doom]

I'd say the duovalve has gone. Its designed to fail in the hot position.

You could get a multimeter across the plug to it, it will be a 3-pin plug, centre pin is common. Test for voltage across the centre and either outside pin.

 

[hoj]

Many thanks to you all for the words of wisdom and the top snaps of someones pussy. Have got a duo valve on the way and will let ya know how it went.............
Hoj