[W126 Coupe] Is this a monovalve problem?

[Dick Spellman]

Hey Tom:

Could be mono-valve then again maybe not.  If you throw the temp dial 
until it clicks in the red, do you get hot air?  If you then throw it to 
click in blue do you get cold air?  If you then throw it in the red but, 
not all the way to the click do you get hot air?

Another way to test the mono-valve(s) directly is to apply 12vdc to the 
2 pin terminal atop the valve and see if you get hot air.  Other 
possibilities are ignition switch, or climate control head or possibly a 
sticking fresh air make up door which would be the two vacuum element 
flap up under the passenger dash.

Anyway, you need to test further and report your findings.  If you are 
inclined, just pull the mono-valve head and see if it's 1. fouled with 
sludge and 2. showing signs of a ruptured rubber seal.  If sludge only 
clean and re-install, if ruptured, replace. ($20-40 depending on where 
you buy MB stuff)

Regards,

Dick
btw:  took a position this past summer in the Northeast for a company 
with US hq's in Sunnyvale (home of fantastic sushi) and world hq's in 
Kobi and Kyoto, Japan (home of world's best steak, would you believe?)  
Same field as before just doing more work for the US govt as a result.  
Having fun too.  Let me know how the new job is going.

.toelsner at comcast.net wrote:

> Happy Holidaze to Everbody,

> Well it is finally getting cold enough to turn on the heater in the 

> mornings...now here is the scenario.

> When the car warmed up enough to turn on the heater, it was only 

> blowing mildly cool air no matter what the temp setting or what 

> buttons were pressed.  Driving speed was 75-85 (hey this is CA).  As 

> soon as I stopped at a light, the air blew HOT.  The next day I tried 

> a variation...drove the car until warm, pulled over and waited to see 

> if it blew hot air.  Air only remained mildly cool.  As soon as I 

> started driving, it blew hot.  I turned down the temp until it blew 

> cold and then turned up the temp...only got mildly warm.  At the same 

> stop light as the previous day, it blew hot.  560SEC has around 165k 

> miles on it.  Does this sound like a monovalve problem?

>  

> btw..saw a great license plate on a new MBZ when in LA earlier this 

> week...hys2pid..maybe it was hys2upid...I was dodging traffic when I 

> saw it

>  

> Tom Oelsner

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