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May 12th, 2012

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04:06 pm - Automotive misc.
Took on a couple minor things on the Mercedes that were non-critical, but had been annoying me.

First was the climate control system. The car has automatic climate control, and it worked, after a fashion, but it was always overshooting in cool weather -- it would heat for too long, then blow cold air for too long. From reading other people's comments on the system, it seemed the problem was likely to be a foam hose that goes to a vent on the dash that samples the air temperature. When it fails, the system samples the temperature inside the dashboard instead of the temperature in the car. I took out the glove box to access it and, sure enough, the 30-year-old foam hose was rotted out. As luck would have it, I'd bought some foam pipe insulation a while back to stuff a costume tail with, and the leftover length turned out to be precisely the right size. I won't get a chance to test the fix until this evening, most likely, when things cool off -- the A/C hasn't worked since God was a boy, so it's really only the heater that I'm hoping will function more smoothly.

Secondly, I went through and troubleshot the central locking system. On this car it's vacuum-operated and of the typical European "all the doors mimic the driver's door lock" style. The vacuum line to the whole system had been plugged off, which is usually a sure sign of a massive leak somewhere that someone didn't want to deal with. There are five vacuum elements that operate the locks -- one in each door (except for the driver's door, which has the control valve), one in the rear hatch, and one for the fuel filler flap. This system has a reputation for being tough to troubleshoot, but it's pretty easy if you have a MightyVac or some other hand-operated vacuum pump; just take apart the tee connectors under the carpet and test each part of the system individually. Three elements turned out to be bad, but two of them were bad only on the unlock side. So, by selectively plugging off hoses, I now can lock everything except the rear hatch from the driver's door, and unlock the passenger door and fuel flap. Eventually I may replace the bad parts to get the whole system working, but at the moment it's not worth the $75 or so in parts it will cost to do that.

(3 comments | Leave a comment)


[User Picture]
Date:May 13th, 2012 08:53 am (UTC)
Congrats on your hose being just the right size, Goldilocks ;>
[User Picture]
Date:May 14th, 2012 03:27 am (UTC)
I spent some time a few weeks back with the Central Locking on my VW A3. The elements were all good (though there is a failed microswitch in the passenger door which prevents the passenger from being able to unlock the central locking and disarm the alarm, though the passenger can lock it and arm it). I used vinyl tubing to replace the couplings on the driver's and passenger's and it works like a champ. Of course, at 18 years old, mine's a whelp compared with your Benz. Would a junkyard romp get you the parts for less? Surely you could test them at the yard with your hand pump before bringing them home.
[User Picture]
Date:May 14th, 2012 06:16 pm (UTC)
Yeah, I still need to take the doors apart and check the couplings on the suspected bad ones -- I know the hatch one is actually bad, though, because I already took the door panel off that one. I find the vacuum hose Mercedes used in the doors actually rarely fails...it's not exposed to the same high temperatures as the under-hood stuff.

Junkyard is a good thought. I might see if Absolut German has any Mercedes of the right vintage...
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