Air Con / Heater help please !

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Messa

Active Member
Joined
Apr 9, 2004
Messages
108
Location
Wigan
Car
CLS400 Airmatic
Hi all, sorry if this is in the wrong section, if it is could a mod move it maybe ?

I have just (3 weeks ago) bought a 2012 CLS and seem to have a weird problem with the heater/aircon. The heater works for a few minutes and then I feel it blow out cool/cold air, not as cold as outside or air con on low cold, but way colder than it should be. After 20-30 seconds I hear the 'flaps' move behind dash and it goes back to warm again. It does it on both top and bottom vents.

This happens if I have it on 21 degrees or on 'max' so it is not the car cycling hot cold to regulate the car and if it is it is way too severe going from one extreme to the other. I think what I am trying to say is this is my 5th Merc on the trot and wife on her 2nd so I am fully aware of how the system should work, it just isn't !

I bought it from Manchester and am taking it in on Friday afternoon so what I am kindly asking is if anyone has any clues as to what it could be so I can go in with some prior info and not be fobbed off with 'they are all like that'.

Could just plain old low coolant cause this, if so would it probably have a leak being only 12 months old ?

Hope this makes sense !

:)

Thank in advance.
 
Not sure if the newer models use a duo valve ,but if they do then thats what I would suspect.
 
Not sure if the newer models use a duo valve ,but if they do then thats what I would suspect.

Thanks for the reply. I did some googling before posting and see why you suspect that but it seems that most people report blowing hot when it should be cold rather than mine blowing cold instead of hot, could it still be that valve even so ?
 
It would depend whether the valve/s stick open or closed,yes it could well be the duo.
 
Just in case anyone drops on this thread in the future I took the car in to MB today and the reset the 'flaps' on the valves/outlets and all is good, I didn't realise until it was fettled how noisy it was in the 'wrong' position. Not sure how the flaps ended up wrong in the first place but it is ok for now at least !
I also got an update to Comand Online, if someone tells me what to look for, version numbers etc, I will post the details if that helps anyone check if theirs needs doing.
 

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