Tricky AC/Heater problem 1982 300D

[300DPETE]

Hi, everyone.

I have a 1982 300D AC unit and heater that were serviced (new brushes, etc.) within the last two years, along with the climate control unit being replaced with a new one….all thanks to a meticulous previous owner.

Well, now both don’t work. Driving it from Tampa to D.C., they slowly started to not work, becoming intermitant until they didn't work at all over the course of nine hours. I spoke with a Mercedes mechanic I know (unfortunately on the west coast), and he suggested that it had to do with the ignition switch. Indeed, when I jiggled the key around for a few minutes, the heat came on through the defroster in a gasp after I switched off the key. I turned it back on again, and got a few gasps out of the AC.

So, I replaced the ignition switch (first with a spare, and then with a new one), but now I can’t recreate even the gasps.

Any suggestions? Is there something else electrical that may be causing this? Can I work my way from the ignition switch to some other device that might be faulty? Am I thinking in the wrong direction?

Thanks.

Pete.

P.S. As a related side note, my glowplug light hasn’t been lighting up (at all), and my mechanic friend said that that might be related to the ignition as well. However, I unplugged the relay (as suggested to someone else on this forum), and the yellow light for the glowpugs came on in the dash when I turned the key---I’m guessing then that this part, at least, is not related to the ignition.

[300DPETE]

any takers?

[bhanson]

Well, I'm fighting similar issues with my heat, although I think you are going to find a solution more quickly than I do. It's very possible you have a bad solder joint on your ACC or a bad switch. If the unit was replaced as you say in response to another problem, such as the motor rebuild, it could have suffered a little damage. The ignition switch may well have been a coincidence. You can try turning everything off, ignition, heat, etc. and then trying to start it with the fan on high and the defrost button depressed. If that works....Well, check the DIY links on that symptom, I forget which step to take next. If nothing....check your #8 fuse first, then start with the ACC.

As for the glow plug issue, if you get no light at all normally, it's almost certainly a sign of a #1 plug bad, or multiple glow plugs bad. Test them and find out.

Good luck!

Ben

[300DPETE]

Thanks, Ben.

Pete.