'91 350SDL w/no heat(er)
Thread Starter
Junior Member
Joined: Nov 2015
Posts: 22
Likes: 0
From: Shelby, NC
1991 M-B 350SDL
'91 350SDL w/no heat(er)
Hot water thru wsw reservoir tubes, temp gauge ok, but no warm air thru heater. Had monovalve reworked today by authorized M-B service place. The old valve was toast but still no heat. Dealer said he cud trouble shoot and diagnosis but it wud be costly. Any ideas please?
Junior Member
Joined: Jul 2010
Posts: 65
Likes: 3
From: Durham, NC
W126 1987 300SDL
If '91 works the same way as 87', disconnect the wire connector at the top of the mono valve. This should set the mono valve to full heat. If you do that and drive at rpm greater then 2k, you should get heat as long as you have the fan on. That should bypass the climate control unit from requesting heat altogether.
I'm sure others will correct me if the '91 changed.
I'm sure others will correct me if the '91 changed.
Thread Starter
Junior Member
Joined: Nov 2015
Posts: 22
Likes: 0
From: Shelby, NC
1991 M-B 350SDL
Thank you very much for the tip. I will give that a try, hopefully today. I see that u are a fellow Tar Heel. I live in Shelby, abt 40 miles west from Charlotte. Thank you for you help, Dave Rose
