Rear de-mist, alternative power supply?
Hi,
Following central locking thread, after another bit of advice regarding the sparse electrics in my old wagen. Rear de-mist has never worked. Discovered reason was previous owner used the power supply for the rear fog light. Suspect this was an MOT fix. Anyway, any thoughts on how to best re-connect? Chances are will need to feed new power line through wagen, best routing options and what power source can I (should I) connect to?
Any help gratefully received. Other option get rid of dog and kids who keep causing condensation?!?
Cheers,
Stewart
I have the same issue so interested in a fix too
Maybe you could take the fog light feed from the tow bar plug ? Just a thought ?
I'm sure someone who knows a lot more about auto electrics than I do (not very hard) will come along soon but before they do, I'd be careful. I would have thought that the rear demist takes quite a load so a feed to a single lamp is unlikely to be much use.
Best way you'll keep blowing the fuse, worst way you'll start melting wire.
But I'm more than happy to be overruled on this as I admit that I don't really know what I'm talking about.
Rear demisters do use a lot of current. They are usually connected to a timed relay but not always.I can't imagine how or why someone would use the rear demister cable for a fog light as the fog light needs a separate switch. Or is the rear fog light activated by the demister switch?
I would reconnect the rear demister to its proper switch via the relay if there is one. Then run a new circuit for the fog light. Is the standard switching for a 460 fog light on the main light switch? Pull it out two clicks?
In other words put everything back as standard. All power should be sourced from a fused terminal in the fuse box.
The rear fog-light was indeed fitted to both my 1984 and 1985 W460 models. It may have been an optional extra, though. It is normally on the lower part of the rear door, about 8" below the door handle.
The flexible wiring to the rear door will eventually break however through the repeated opening and closing the door over time. and so a quick fix for the previous owner may have been to swap to the rear heated screen wire instead. Remove the door card and look for an unconnected wire in the rear door cavity. If you find one, it is likely to be your original fog-light wire. You may then need to repair this wire in the flexible section, between door and body, before swapping the wires back and reconnecting to the fog-light.
You may want to replace/splice all the wires, from just before the start of the 'flexible' section as they will all fail eventually. I have done this in the past.
The wiring system for the rear door was improved in the W463 because of this problem.
W460 Wiring:
http://www.benzworld.org/forums/g-class/1728641-1984-230ge-w460-rear-door-wire.html
...and how to upgrade to W463 system:
https://www.youtube.com/watch?v=qn0OO9_Mcyc
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Thanks for all the comments. As suspected an 'easy fix' probably isn't apparent and as Roly points out probably best to go "original". Yes 460 fog lamp is pull out 2 clicks and this is what works. Assume that fog lights weren't fitted on '87, although in switch? Or at least an independent fog light wasn't fitted? Anyway, as became MOT regulation (or re-wiring or whatever) the rear de-mist became the donor power source. One possibility is to re-connect de-mist to original circuitry (hmmmm, find relay etc?) and perhaps use tow bar fog light power for fog light (as suggested by neil).
Like the 460 due to 'limited' electrics, but even these are fun. Has a number of interesting (character) electrical gremlins. Nothing serious, just amusing to slightly annoying (depending on mood) but very intermittent. Oh the joy! But then using a 30 year old car as daily run around, what do you expect? Trundle on.