Heater always on

[Magyar]

Hi , I have a w 116 mercedes and the heater is always putting out warm air through the vents.

How can I fix this?

[rumb]

Start by reading this:
https://handbook.w116.org/Climate/


Check the heater hose valve on firewall, next could be vacuum pods.


Do you have manual system or dreaded chrysler?

[Rolo]

I experienced the same with ACC.  Replaced with UWT electronic controller.  A big mistake.  Rebuild the existing unit.

[79W116]

I experienced the same with ACC.  Replaced with UWT electronic controller.  A big mistake.  Rebuild the existing unit.

What is a UWT please?

[daantjie]

I experienced the same with ACC.  Replaced with UWT electronic controller.  A big mistake.  Rebuild the existing unit.

What is a UWT please?

Unwired Tools

[79W116]

I experienced the same with ACC.  Replaced with UWT electronic controller.  A big mistake.  Rebuild the existing unit.

What is a UWT please?

Unwired Tools

Ah, perfect, thank you.

[Rolo]

Failed to mention that full heat is the default mode when the ACC controller fails.  Also, only consider rebuilding the ACC controller if it is the aluminum-bodied aftermarket one.  I assumed that's what you have since none of the plastic original equipment one survive this long.