BenzWorld Junior Member
Date registered: May 2003
Vehicle: '86 MB 300E
Location: Seattle, WA USA
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Temp Control problems...
I writing about my '89 560 SL, but I think this MIGHT relate to other models.
I just purchased my 'SL with 109K on the clock. I noticed that I was not getting ENOUGH heat.
My mechanic diagnosed that it was the MONO valve, and replaced it. Now I have the following problems. BTW the ambient temp has been between 40 and 50 degrees F.
1) I am getting MAX heat in all except the lowest temps on the dial (18-20) as soon as I move the dial near 22, I get full heat. My '86 300E would give me gradual heat as I turned up the dial.
2) When heat is on, center vents stay open, and very little heat goes to the floor.
3) When DEF is on, most air goes through the center vents and much less through the defrost vents.
Not sure of what to look at, and would love some ideas before I let my mechanic loose on the car.