OK... Same problems, different twist...
81 mercedes was purchased in summer 2011 (in Houston, Texas) in great shape with a new updated air conditioning system. The air con system works great! Then weather got cold. No heat. Got the usual dialog and have read all of the blogs about how problematic this system is, etc...

One mechanic says SERVO looks good, I need a new climate control panel in the car. Bought that on ebay and changed it out... No heat! Everybody points their finger at the SERVO. One mechanic has me do the "turn the ignition switch to acc and turn on Defrost and listen to the SERVO - still no noise ... You need a new SERVO!"

Bought a new SERVO and installed it... Still no heat! Whats worse "turn the ignition switch to acc and turn on Defrost and listen to the SERVO - still no noise"...

It's freezing outside; temperature gauge set at 85F; car on; system comes on and blows ambient air; also center vents not blowing air. I can prop the vent open (through the center vent) - it's not broken, looks OK. Also appeared to cycle open and closed on me when I first started the car. I know there is this whole thing about a vacuum leak, and It is possible that I wind up pulling the gloove box/dash and start troublshooting vacuum leak/looking at vacuum/pods, etc.

But I still believe that if the SERVO was delivery hot water to the heater box, I would be getting some indication of warmth inside the vehicle - but nothing! I'm just not convinced that this is happening.

Hot water pump (mounted between the SERVO and the overflow tank) not working?
No power to the SERVO?
SERVO amplifier hosed?
A short in the electrical to the SERVO?
Something else?
Anything else?
Everything else?

I also understand that I could be looking at a number of problems, but I have gotten to the point that I don't no where to look. Also it is possible new air cond installation mechanic defeated heater because there was some problem. There seems to be an "it's OK to defeat features and live with it" culture on this car. Have had a number of mechanics suggest I forget about it and park the car in the winter. Me? I want to fix the problem.

Can anybody coach me here?

Inside the car behind the glove box is the "amplifier" that tells the servo to move.
Sounds like your issue.

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OK...
Makes sense...
I've looked behind the gloove box and it is pretty crowded.
Could you coach me into identifying the amplifier?
(tried to paste a picture but was not successful.)
Looks like little black box with holes in the cover?
[IMG]file:///c:amplfier.jpg[/IMG]
I can get to the top through the gloove box, but looks like I need to remove the panels beneath the gloove box to get to the bottom and get it out of there?

Advise me where I can get another one?

Blog PeachTree with problem and mbdoc suggests that I should look at the amplifier (see above post).
Take it to local MB mechanic for new Amplifier
Local MB mechanic says its not the Amplifier, its the Servo
I pull the Servo out and return it (strangly I recovered all of my money on that)
Dermine auxialliary pump is frooze and plumb hoses so it is out of the picture.

Contacted Unwired Tools and talked to them...
Buy Unwired Controler and it arrives just as promised...
Install it perfectly; it is not that hard ...
But still no heater...
Everything works perfectly with the air conditioner; fan speed, vents, bi level, auto hi, auto low, you can freeze meat.

Start car with thumb wheel set to 85F push defrost; AC switch on off
Still no heat; in fact it is cold air!

Check thumb wheel on Environment Control unit in the dashboard according to Unwired Tools Instructions; 1200 OHM differential ; checks out OK
I take new Unwired valve out of the picture and flush heater core to determine if there is a blockage; no blockage.
Run a flush on the engine block inklet and outlet; no blockage.

No matter what I do, I have the exact same thing; full on cold air regardless of the temperature; regardless of the AC on/off switch and regardless of the tumbwheel postion and never, never any heat or breath of warmth coming out of the dahboard on any setting.



I no longer believe this is a Climate Controller issue - New Servo; Unwired Tools fix (which takes the place of the Servio and the amplifier) all return the same results.
I have read about the vacuum testing sequence on the flapper valves behind the dash (through the glove box), but I think I need an idiots guide, or some specific coaching to do this.
Is there a flapper valvethat blocks the flow of hot water through the heater core when the car is running? Is there a flapper valve that exposes the heater core to the blower that refuses to open?



Am I looking at some repair on the heater box?
Got any thoughts? Troubleshooting instructions.
Help!!!

All problems are fixed with this product...