[Guest (MBNZ)]

My heater controls will not change the ouput of air. It heats fine but I cannot control where the air exits. If I have the defrost button pressed it comes out the defrost. If I have the up/down button pressed it comes out the vents with a little coming out the defrost and heater. If I have the down button pressed it comes out the vents. I know it is both vacuum and electronically controlled but cannot find the problem. Is this vacuum system connected to the central locking system? (Locks don't work either) Can I change it to an electrical/mechanical system. Where can I find a diagram for the heater (vacuum and electrical). Thanks Kevin

 

[Guest (MBNZ)]

From what you describe, I can't tell exactly - but I bet you have a vacuum leak (which is why your locks don't work.) This also does affect the vent actuators, although the fact that they do anything is a good sign. In addition to the leak, it is probable that at least one of the vacuum actuators have failed (won't hold vacuum.) This is very common when the cars become older. It's also possible that your pushbutton unit is acting up, this is also common... you can either get a rebuilt unit for ~$150 or try resoldering yours, that works about half the time.<br> <br> Find the vacuum leaks first, and either plug off the offending lines or fix the leak (new fittings or actuators.) Then see if the ACC works properly. <br> <br> Have fun!

 

[Guest (MBNZ)]

Kevin, I have the same problem and have narrowed it down to a vacuum leak. Does your engine have trouble shutting down? Mine does, in addtition to the central locking problem. However, when I shut off the ACC system, the fuel shut-off works fine, and the door locks function except for the right front door (one of my leaks). I will be taking the consose, etc out tomorrow to find the leak in the ACC (probably floor flap control) and wiil let you know, in the meantime go to http://forums.mbnz.org/forums/W123/vthread.asp?messid=80 for an excellent article on tracing the vacuum leaks in the locking system to eliminate that problem first, as it's easier. Note the typos in the article-red stripe should equal unlocking line, green is locking line. I'll get back to you after I find my ACC vac leak which sounds identicle to yours. John Wieland

 

[Guest (MBNZ)]

<br> I had trouble like this and fixing the vacuum leak did it. Trouble shooting the vacuum locking system isn't too hard. Just find the bundle of tubes under the driver's side carpet and isolate the leak by plugging one at a time. Use a small hand held vacuum pump to do this. Like the other guy said on the post, red is locking, green unlocking.