Can't turn heat off

[Steve2500]

Cant turn heat off, any suggestions?

[Steve2500]

My 73 450sl heat is on all the time and is cooking my feet! The control to move the flow from floor to defrost works and temp adjust works some. Any suggestions would be great.

[TX76513]

Look at Heater Valve - the vacuum line may have come off, leaks, or failed. Or the Valve may have died leaving valve in "ON" Position

[Steve2500]

Thanks for the response. Is the valve under the hood or in the dash?

[Steve2500]

Is this under the hood or in the dash?

[Pooka]

There is a service manual for this and it is on-line somewhere.

If you have the automatic climate control then your servo is likely not responding. This can be due to a number of reasons and without the manual it is almost impossible to figure the system out.

By the way, the servo can be rebuilt but it is a time consuming job. At least there is nothing heavy to deal with.

For the short term.... Just disconnect your heater hoses. Put a union in and just run one into the other. That's what your heater core does. This is not a fix of course, but it will stop the heat from pouring into the cabin.

[meltedpanda]

hood right at fire wall, drivers side , easy fix if broken also can close it manually if vacuum if messed up. Could also be microswitches at temp sliders

[meltedpanda]

if its a 73 he does not have a servo

[Palolo]

Originally Posted by Steve2500

Cant turn heat off, any suggestions?

http://www.peachparts.com/shopforum/sl-forum/69504-heat-always-1973-450sl.html

[Pooka]

Originally Posted by meltedpanda

if its a 73 he does not have a servo

Thanks for the info. I have never seen a 450 SL from the 70's that did not, but then the 1973 is rather in a class by itself in a lot of technical ways.

To me this is just one more reason to look for a 73 if I ever wanted to drive a 450 SL. I have had trouble with every Mercedes with the Servo system I have ever owned so I learned how to tear the servo apart and rebuild it.

And all of those vac crossover valves behind the dash.......!!!!!!

[meltedpanda]

I have a 72 and no servo, I dont think the servo showed up until after 75 or later