Mercedes-Benz Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
So far to fix this problem i changed my thermostat, disconnected my heater core completely and backflowed with the garden hose. I also checked the power at both the circulating pump (if this is the correct name) and power at the valve at the firewalll. I then used alligator clips from the battery to insure that both were operating. They both seemed to work when powered up. I found that after warming up even while driving only cold to luke warm. If i come to a complete stop for a few minutes i will get heat, but as soon as i get moving it stops again.

Please help i am cold!

Thanks
 

·
Registered
Joined
·
52 Posts
I have a similar (but not the same) problem now on my 1985 300D Turbo. The heat is either all-on (if I rotate the temp scroll wheel up past the full heat detent) or all-off if the temp scroll wheel is anything less than full hot.

Is the fix the same for this problem too (monovalve)?
 

·
Registered
85 300D, 84 300D, 05 Mustang GT Vert, 11 VW JSW TDI, 95 Del Sol, 88 IROC, 95 Villager, 04 Wrangler
Joined
·
602 Posts
When you hit the monovalve with power, it should shut, and you will have no heat. Removing power should open it back up and you should have full heat. Check the diaphragm in the monovalve for a tear, and hit it with voltage while you have the innard's out. You should feel it open and close.
 

·
Registered
73-450SL 73-280C, 83 300cd turbo disel 86-560SE 70-280se 99-ml430 02-clkl55, 77 Datsun 2800z
Joined
·
8 Posts
I have no heat, disconnected the power to the monovalve, and I have full heat when the car is stationary and at very slow in town speeds. At highway speeds, the heat decreases and gets to cool for comfort but does not totally go away. It is like it is taking in ambient air from outside, or perhaps the air is cooling the radiator and circulating water to much? Does anyone have any suggestions. It is difficult to enjoy during the cold months.
 
1 - 6 of 6 Posts
Top