1983 500 SL Heat will not shut off - PeachParts Mercedes-Benz Forum

nh500sl · #1 12-12-2010, 11:54 AM

I have the above mentioned Mercedes. I had as situation a few years ago where the heat would not turn off. I went to look at the heater control valve and unplugged it and pluggedit back in, and everything worked okay.

Well I think that I have run out of luck as I tried that yesterday and that did not work. So at this point I need to determine where the problem is. Is it the switch, heater control valve, vaccume line or?

Any ideas on this? Thanks, Nick

rowdie · #2 12-12-2010, 02:12 PM

Which climate control system do you have?

nh500sl · #3 12-12-2010, 07:34 PM

It has the automatic climate control. It has the roller on the left to control the temp and the two fan settings with the auto buttion between them.

abiby · #4 12-12-2010, 08:03 PM

That should be the ACC III system.

Easiest recommendation would be to install a monovalve repair kit.

meltedpanda · #5 12-13-2010, 07:56 PM

all heat all the time is defult for bad ACC control unit or bad monovalve . I would start as mentioned with Monovalve

nh500sl · #6 12-14-2010, 07:27 AM

Okay sounds good. I was hopeing to find a sure way to diagnose wich componet is bad, but it sounds like the consenes in is on the Mono Valve.