380SL Heating Problems

[slLover]

Hello! I get absolutely no heat (only cold ac air) out of my vents. Is there any way of checking or overriding the system? 380SL 1983.
ThankYou!

[Steve Gutman]

If your heat just quit you may need a new mono valve. Five minutes and four screws. It worked for me.

[JRC]

Where is the mono valve and is that a flap that open and closes when changing AC to heat?? that is my problem..

[Steve Gutman]

I recall that the Mono Valve is on the top of the engine bay back by the firewall. It has the heater hoses going to it. Can't remember right or left side but google image it and look. It is the easiest job there is. With that said I have broken a hold down bolt on a BMW. Good Luck.

[Steve Gutman]

The flaps that control the air flow are under the dash. I don't remember the procedure but I think they only control Defrost, middle or flow to the feet. I think the switch form AC to Heat is through the heater valve and the AC system. Not sure, sorry.

[JRC]

thank you and sorry you broke your bolt lol

[Steve Gutman]

lucky it was on a parts car The Mercedes seem to come apart and go together better than other cars. THat was a BMW.
Steve

[Mike1953]

Had the same problem with my 1981 380SLC. Heater servo valve was not working and after buying a replacement (and it did not work either), I switched it out for UNWIRED tools replacement - and problem solved! If you are having the same issues don't bother with the heater servo valve replacement - in fact you get to throw it away! Just Google Unwired Tools for more info, pay the money and fix the problem.

Of course you could still have other problems, such as vacuum leak, pad control pod, etc. which will not be corrected with the Unwired Tools replacement fix.

[JRC]

I wish the heat would stay off... If I turn my AC on and off sooner or later the ac will stay on???

[rowdie]

JRC. What model and year do you have? Which AC system? Only the '78-'81 had the ACII system that Mike1953 described. The '83 in the original post has the ACCIII system.

[JRC]

85 380sl

[rowdie]

ACCIII. Check section 3 of the climate control section of the manual. Model 107 It has info. on the mono valve and testing operation of the system.

[JRC]

Ty