420 sel climate control
 

As a new owner of my first mercedes, I am slowly working my way through the typical problems. So far I have taken car of all except my climate control. After reading every archieved thread on this board (and mbzn) plus having a local shop check it out, I am still puzzeled.

Symptoms-----when heating I get warm air out the side vents and cool or cold air (depending whether or not I have A/C Selected) out the center and lower side vents. The flaps are not changing position regardless of heating or cooling but the heat does cut off if the temp set point is higher then inside temp at which point I will get cool air from the upper side vents. Defrost selection give warm air out the upper side vents and window vents. I think the center vent is still open but cann't remember and the wife has the car.

I took it to a shop this week and the mech said all six (?) vacuum valves are leaking vacuum and that sometime in the past they were bypassed. No other details.

Question-------doesn't it seem strange that all six valves would fail? If so, where is a good source for these valves. I can not find them in the online stores under the climate control section.

tks for your help

Not likely that they are all bad. The defrost defaults to "On" meaning if you ever aren't "On" then it holds. The center duct defaults "Off" so it must be holding since its working and not in the default position.

I checked the first number and fastlane had them. Here are the numbers to put into the "Search by part number": 000 800 57 75 main air flap (recirc), 000 800 58 75 main air flap, 000 800 43 75 Defrost, 126 800 14 75 legroom, 000 800 67 75 center duct, 000 800 40 75 air scoop (?).

If you can replace them then you can check them. Some are a b**** so identify those you feel are leaking then decide if you can get to them.

Flap Positions Clarified
 

Steve, thanks for the comments and part numbers. My wife just got back so I was able to take another look. It seems that in defrost, the center vent is open and the fan goes to high speed. In normal operation, it appears that the defrost vents are still open and I think the whole system is stuck in recirc.

What is the best way for a DIY to check for vacuum leaks on the valves?

tks again for all your help.

Update
 

Just chatted with the shop and they said that all the valves are not really bad, but, while they have the dashboard off we might as well replace all of them. The quote was $800.00 parts and labor. Does this sound reasonable?

Litton

I've been following this thread .... I would have them replace them. Considering you are already there and have the labor into it. I would say they are offering a fair deal.

Haasman