W123 Center Vents
 

I got everything working in the dash on my new (to me) ’82 300D, except one nagging thing….
These darn center console-mounted vent flaps refuse to work properly! I’ve checked everything I can think of and the only way I can get them to open is to either use a jumper lead, or connect it to one of the other solenoids (like the one for the floor vents). Seems like there is a lack of ground to the #3 solenoid, but I can’t make it happen except to short it with a jumper lead. All the other solenoids work as they should.
What am I missing?
Any help is appreciated.
I'm setting her up to run on the veg.
Kerry

Solenoids? Are you talking about the vacuum pod that operates the "gate"?

I think he or she is talking about the switchover valves behind the climate control panel which control the vacuum to the various pods.
I'd probably try a new switchover valve.

If I understand correctly, you can get the center vent to work using jumpers to operate the solenoid and you can get it to work by connecting the vacuum line to another solenoid, right? If so, then the solenoid and the vacuum pod are both working, which is nice since the pod failure is common and hard to repair (have to pull the dash).

Which ACC unit does the 1982 model have? Does it have vertical or horizontal pushbuttons?

You may have a bad contact in the ACC. That would prevent the solenoid for the center vents from being energized. Another possible cause is a damaged wire. You will have to do some tracing. It's a slow process.

Another thing you might want to consider is to modify the system so that the center vents are open all the time. That way, you will get heat out of the center vents in the winter, which is very nice. Do this by removing the glove compartment and then the rubber sleeve that connects the air box to the center vents. Now you can see the metal lever that opens the flap to the vents. It is held to the flap by a plastic pin. Remove the pin and open the flap with your hand, jamming it under the lever. Put the sleeve and the glove box back and you're done.

If you're gonna go veg, do it properly and put in a two-tank heated system. Too many W123's have been ruined by poorly installed junk conversions.

Jeremy

Thank you and update:
 

Thank you for all the info and suggestions.
We have been gone for a mini holiday and are just back, and it is nice to see your replies.

An update:
To answer the Q about the button lay out. They are horizontal.

Also, I had purchased a new (it may be a rebuild?) head control unit, a "Programa", and when I hooked it up it did not operate any differently. Same dead center vents.

The dash is already off, so I don't have a problem delving very deeply into this to make it work as it should.

Two questions pop to mind:
Is there a good wiring diagram I can access on line for a this car that will help me track down a poorly conducting or severed wire to this sysyem. and;
Is it possible there is another computer somewhere I don't seem to be seeing in the circuitry?

Thanks in advance for your input.
This is such a nice car, I really want to make this car work as it came from the factory. (Except for the VEG thing, of course!)
Kerry

You are aware that those center vents only work on A/C, not in heating mode? Designed that way by Black Forest Elves!!

Manual (as in repair)
 

Try Here:

http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Main.html

And here:

http://www.detali.ru/cat/oem_mb0.asp?TP=1

Did you try to hook up a different solenoid? They are only held in by one screw. Just move one of them over so the center vent connections will fit. I had a problem with one of the solenoids a year or so ago, it was sucking air from the bottom..I just put some gum or something to plug the hole that was leaking.

After that, I would check the pins on the connections (wire side) that attach to the ACC.

Fixed!!!
 

Thanks to all kind the members who relayed helpful advise on my issue. We repaired the computer's circuit board and all issues are gone. Works like it should now. Thanks again, K.

You mean this was defective as received from Programa?
Did you tell them?
They are usually very reliable.

My wrench has been beating his head against the wall on a 107 with an a/c controller problem. He has gotten a couple of bad "rebuilt" controllers from Programma and is understandably bummed.

Programma
 

Yes, that appears to be the case. They took the one I bought back no questions though.
Thanks for all your help.
K