I can't figure this out. I believe I have the right one, but maybe hooked up wrong. My understanding is 68-72 looks like this:


Which I have.


And 73 and on looks like this:


I had played with it and wondering if I have the linkages wrong. I'll shoot some pics of the dash and valve in a few min.

Anyone a heater control valve guru? It's getting hot.

Here's what I have going on. It doesn't seem to close all the way.

I'm thinking I have the arms off 90 degrees. They are on square pegs. If I go 90 degrees ccw, I should be able to shut it off, but it won't open 100%. Like the cable lengths never match.

The other style really doesn't seem like it matches with the passenger side cable location, as well outlet hose.

The car has a book in the glovebox with dealership locations in South Africa. If that helps. Lol.

Hi Lucas,

That heater control valve issue seems to have you talking to yourself!

I don't know the answer. I looked at the W113SL page on Heater Control Valve to see if it might give you a clue. See here --> Pagoda SL Group Technical Manual :: Electrical / HeaterControlValve

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1957 Ponton 220S
2001 S600 Daily Driver
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Well I'm hoping for a two way conversation with someone that knows these valves. Haha.

Thanks, that setup is different that mine. Good idea on the plumbers putty.

If someone has an early 115 (with working valve) and can snap some pics of the cable setup at the firewall, that will give me some answers.

Hi, have a 76 300D and my heater control value is like the 2nd one pictured; where no heat (both lower red slide levers in the middle) have the arms away from where the valve would bolt to on the firewall and heat (lower lever to far right and far left) and lever closer to the bolts. I also have 3 hoses connected, picture only seeing 2

hope this helps, Sal

Anything helps! I have 3 hoses. Intake and driver core come out the front, passenger core out the side.

Do your cables coming out of the firewall look more spread apart?

I am not sure I understand your question, but it is apparent that one of your cables is not hooked up to the valve. Did you do this for the photo?

These valves, the first on you have pictured, will gum up inside due to the O-rings in there wearing out. Replacing them is as simple as pulling the valve out of the car, taking out the snap rings that hold the valves in, and replacing the O-rings. Lube the O-rings before putting the barrels back into the bronze housing and MAKE SURE you remember which barrel came out of which hole and put them back in the same way they came out.

While you have it apart you might also use some fine grit sand paper inside the housing to remove any crud build up. Lightly now; a little will go a long way.

They are unhooked so I can shut it off manually.

New orings and cleaned.

They function fine without the cables.

I believe the levers may be in the wrong position. That's what I need to determine I believe.

Or maybe it's completely the wrong valve, but thus far it seems right.

But I still don't get the full slide of the cables on on position, this may be normal.

I don't understand what the question is either.

Looking for some detailed info on operation. I'll shoot a video tomorrow that will explain the problem more.

First position is full heat. Shown on the valve and in the cab.




If you unhook the drivers side cable you can turn the valve back towards the firewall a little more.

Second set of pictures is heat off.

To actually get the heat off you have to unhook the cables and turn the arms clockwise another 1/4"-1/8" of a turn.

I think I need to remove the arms and turn them 90 degrees CCW in respect to the barrel. But I don't incision this giving the dash control full range. When I slide the dash to full off the cables stick out farther than any position possible on the arm.

Maybe they will work, but I don't get full 100% heat. It will be the same as now, only I can hit full off instead of full on.

It could be the design, but seems weird to have the extra space on the dash sliders. Maybe someone swapped the cables. From everyone pics they sent me my holes in the firewall match this type of valve.

People selling valves on eBay claim that this type of valve is for 68-73 and the other with the arms on the side are for 74-76. However, one forum has a 72 with the updated valve type.

In retrospect this car had a fuel filter assembly from a 76 240D.

It's gonna take an old guy with experience with those cables to determine what's going on.

Maybe I should find a source for cables and get some dimensions of the end lengths. Maybe you have an early 115 220D and want to measure them for me...

I obviously cleaned this thing up and put generic o-rings in. I've ordered the right rings from mercedes now that I know it's the right valve.
I documented the valve before disassembly with pictures. I'm pretty good about that. But this car had seen some novice work, so I don't count on the guy before me having it right.