Heat or no heat
 

I have an 86 300E and the heat is always on, no matter where the temp dial is. And it always blows out from the defrost ducts. Anybody have any insight on this always heating problem.

And what temp thermostat should a 3L have in it?

Thanks Nels

There are several possibilities:
Your Mono Valve is stuck open
The Fuse is blown to Mono Valve and it's default is "open" e.g. heat
Your Mono Valve is shot
Your CCU is broken

I am sure others will chime in with other ideas - but the mono valve is the most common problem.

and if it's coming out of the defrost vents there is an issue with vacuum supply or vacuum diaphrams in the climate control.