Heater issue

[wrcarter]

On my fathers 94 c200 the heater constatly blows in warm air from the engine. The car does not have air con. It is the same as if the blower is set to the dot between 0 and 1 even when it is at 0. This problem is really annoying now that it is summer. I have searched the forum and have read that it could be the duo valve. Where is this located? Any advice much appricated.

 

[television]

Its 117 in the link young man they fail in the hot mode

http://www.detali.ru/cat/oem_mb2.as...417717.418&CT=F&cat=44V&SID=83&SGR=180&SGN=05

 

[wrcarter]

Cheers, will replace it with a second hand one and hopefully that solves the problem.

 

[wrcarter]

Just looking at the link in more detail and whats the difference between 115 and 117. Does one control each side. I think both sides are gone but can check later. Would both sides fail together or would it be something else then?

 

[television]

117 and 117 are the same thing, the duo valve receives a pulsed voltage from the control unit, 0 volts out from the control box = hot and the full pulsed voltage = cold, a multi meter will indicate a reading re the voltage and could be something like 8v when set to cold

 

[Dec]

This will give you a good insight into the subject… http://forums.mercedesclub.org.uk/showthread.php?t=18785

Dec

 

[Quick Silver]

I have a similar problem on a Vito 110 cdi which uses the the 220cdi engine only the other way round , the aircon works fine and the heater is permanently cold irrispective where you set the temp control , the temperature only varies with the ambient air temp . The engine temperature is normal and rises to normal from cold quickly and is then controlled by the thermostat so no problems there .

Any body any ideas as to what the problem may be ? It's a problem I can live with now but come Sept it will need to be sorted as the weather will be getting colder.

 

[Dec]

How about unplugging the duo valves and go for a 10 minute run to see what happens.
You could also try tapping both valves with the handle of a screwdriver.

Dec

 

[television]

I have a similar problem on a Vito 110 cdi which uses the the 220cdi engine only the other way round , the aircon works fine and the heater is permanently cold irrispective where you set the temp control , the temperature only varies with the ambient air temp . The engine temperature is normal and rises to normal from cold quickly and is then controlled by the thermostat so no problems there .

Any body any ideas as to what the problem may be ? It's a problem I can live with now but come Sept it will need to be sorted as the weather will be getting colder.

If the circulation pump has failed, then always cold air

 

[Quick Silver]

If the circulation pump has failed, then always cold air

Are you refering to the water pump Malcom ? or something else .
There is a good flow of water through the header tank once the engine reaches operating temp .

 

[wrcarter]

Cheers for the help lads. Checked the voltage going to the duo valve. Its 0 at hot and 14 at cold. there is on variation in voltage as the switch is varied. Is that correct?

Also if i left it unplugged it should therefore blow hot air. Will take it apart tonight and see if it is blocked.

 

[television]

The control unit should should be plugged into the duo valve when testing as it needs to be loaded.

It sounds as though the valve is just stuck