intermintent heat 1985 500 sel
 

I have a 1985 500 sel 5.0 with 204,000 miles. Great car with a resolvable problem if I can be "smarter" then the MB.If i have the heat on and the temperature turned to any setting or max before I start the car it will provide heat, until I depress the throttle to pass another car. if I adjust the temp it quits. The fan works properly. it acts like the hot water to the heating coil just shuts off when I accelerate. when I shut the engine off for 15 to 30 min, it works again until I repeat the above. sometimes I "wiggle" the heater hoses at the firewall and it works again, but will shut off under acceleration at highway speeds. I use the ecomony setting on heat mainly but the problem exists no matter which button is pushed.It will work for hours unless I try to adjust the setting or give it the gas.One last thing if I start the car and "then" try to get heat only the fan works and no heat what so ever no matter how much I fiddle with the settings.Any thoughts on this would be appreciated greatly.

Check the diaphram on the mono valve capsule. Its probably torn. if so replace it.

intermintent heat 1985 500 sel
 

Thanks steve
went out and took that valve apart, I now have a new one on order
thanks much for the assist
Cliff