w126 300se heater problem

[mjcr666]

hi all, ive had this problem with my heater ever since i had my radiator fitted on my car. when it was fitted the heater decided to run cold when supposed to be hot, so i flushed the coolant out and restarted with new coolant. now the heater works well !! but its always hot whether i turn it to cold or not. only cold air i get is when i open the air vents and it comes out cold its all very weird and if anyone knows what the cause is or how to fix it, then it would be a great help
thanks
mike

 

[jaymanek]

hmm sounds like the duo valves are stuck open to me.

 

[mjcr666]

i havent a first clue of what that is. how do i go about repairing it ?

 

[ianrandom]

Its really nice and easy. I have a guide on my home PC, but if you google it you should find something. The duovalve is located inbetween the two firewalls. there are two rubber diaphrams inside that may be split. Unfortunately you'll have to buy new ones from Bosch or MB or somewhere but its a very quick job once you have them.

 

[mjcr666]

ahhhh thanks alot !! its been bugging me alot lately. very weird though because when i use the kick down the heating goes cold all together :s

 

[ianrandom]

Ah, that actually sounds like it could be the magnet which is in the duovalve assembly, according to a problem i remember reading about. Somebody that had less heat with more revs. That person changed their rubber diaphrams with no joy but when they did the whole insert it fixed it. If you buy the new inserts the magnets are in that. Not very cheap though i'm afraid, unless you can find some good on ebay. Or i can recommend a helpful used parts guy that might have something.

 

[mjcr666]

ok cool, where is your parts guy based ? im in worcester you see. ill have a look on ebay as well just to check if theres any on there. thankyou for helping so far

 

[ianrandom]

The guy i've used lots for parts, is actually two guys, Rob or Ade. They sell stuff on ebay, under robparker123 i think, they've saved my bacon a few times. Their email address is [email protected]. They're in Somerset but they post, obviously.
You might end up having to shell out for a new one, but its well worth trying ebay etc first. Mine was only 99p but i got very lucky, didnt even need one at the time but it came in very handy!
New, i seem to remember they are about £130 each side? You'd need two. MB dealers sell them but apparently they can be got cheaper from Bosch if you have the part number.

 

[mjcr666]

ok cool thankyou for that mate !! ill give them a go and see what can come of it. thank you again !