following my continuity testing, I connected a 12v 50w headlamp bulb to one
pair of wires and hey presto......we have light. (when Ignition is turned
on, so they are on all the time)
I did not disbelieve anyone it was a case of a number of different
So the conclusion is while the mirrors had electrical continuity, they must
be broken somewhere.....but why this is so needs an electronics eggspurts
MOT tomorrow then if she passes its a new pair of mirrors.
My guess would have been the mirriors too, what sort of continuity readings
were you getting? Hi - 100k ohms or low - 1 ohm? Anyhow, glad to see it's
not the wiring, and thanks for the follow-up.
well I tried fitting the relay but it was a bit of a failure.
Bought all the parts, relay, crimps, wire etc
disassembled everything, found 10A wires no problem.
The problem started with the large "white" wire going to the rear window
heater. In my A4 2.6 SE this wire is Black and it is live all the time. When
the rear window heater switch is operated the voltage at this connector does
drop a few 1/10 volt but never 0. Looking at my Haynes manual although it to
indicates this wire as white, it does show a linkage to the fuel injection
system from the rear heater switch board. I tried all other wires, those of
a size (10/15A) and non were connected to the switch. I am unsure how this
system works as the rear window element is only hot when the switch is
active. I thought for a moment the rear heater was on all the time
irrespective of the switch.
So I have shut everything up and will just fit the new wing mirror glass
which will be on all the time, well until they burn out. Would it be
possible to wire in within the wing mirrors say a high resistance resistor
(one of those in an aluminium block) to take some of the power thus reducing
the load on the mirrors but maintaining a little warmth to the glass
It was worth a try and something else to put on my CV.
I don't have my Bentley nearby, and it's not for euro spec anyway, but lets
see if this will work.
How about placing a relay inline with the existing heated mirrior wiring,
and have it controlled via the load side of the rear defroster switch (or
relay)? I don't know what the AW article does, but that's probably the way
I'd do it.
(Based on my electrical engineering/electrician experience, not neccessarily
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