My wife drives a W116 300SD. Boy was she tired of not having any heat. Amusingly enough, when her heater control servo failed, it actually failed in the 100% on (hot) mode. I clamped off the heater hose with some vice-grips for the summer, and come fall it had transitioned into a 100% closed (cold) state. It has been geting down below freezing at night and the car is pretty cold when she drives our children to school in the morning.

So, today I installed the Vintage Air "Servo Heater Valve Re-fit Kit" (part #50507-VUA). I think I paid $88 + shipping direct from Vintage Air.

I still have the heater control servo installed for fan and vent control.

how did the install go.. can you give a detailed install walk through?

were you able to retain a/c control?

Not a very user friendly website.
Do you have pics?

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I found this - http://www.auto-motif.com/heat.html

Looks like it replaces only the heater valve and adds a separate temp control knob. The rest of the ACC works as before except that temp isn't controlled to a setpoint and defrost can't automatically set the heat to full. Ideally you could wire this valve to respond to the ACC signal.

Sixto
93 300SD

It would probably be easier, faster and cheaper to swap the whole dash with the manual controls from a 240D.

To my knowledge, a W123 dash won't swap onto a W116.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Doh, you are right. I had W123 stuck in my head.

That's an intentional fail-safe mode. It's uncomfortable to have too much heat when you don't need it, but dangerous when you need heat and don't have any.

There's always the pre ACC set-up from a 73-75 116.

Sixto
93 300SD

I have a servo that failed stuck in the heat OFF position. The real problem is when they crack and leak coolant and your SOL
I was lucky to find a low mileage rebuilt servo for the 123. The 116 servo is slightly different and as a result they are not interchangable.
I was getting warm on replacing the servo with that kit from Perf Parts but in the 300TD there isn't much room around that area because my vehicle has the SLS reservoir right next to it. I couln'd see where all the parts would go and I determined it would be far quicker to replace the existing servo even if that leaves me open to future problems. Cursed things!

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

what would be involved with the swap?

I have access to to an 83 240D and an 84 230E

Having had that job right in front of me, there is soooo much more to it than you would think. (W123 to W123 that is).
You think "well, I will just swap evap assy's and be done with it. Well, tap the brake a minute. There is gonna be hardware issues of course, but the electric portion with all the different wiring harnesses is a puzzle that will require some time and effort and gray matter. The wiring for the different knobs, the illumination of said knobs, fan speed, compressor circuit, etc.......
I'll be very impressed when somebody does this.
Dave, you are the most qualified........
I said screw it, and just bought a 240..........

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Have a look at my post "240D litany of woe!". And I'm not even trying to swap stuff between cars

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S