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Discussion Starter #1
I'm having a problem with front fogs ( recently fitted ) and now blowing the fuse, where they were fine for a month or two, so guess I've somehow got a short in the loom I fitted ( it's been in the garage for a Cam Belt since fitting fogs ) and I'll have to try to trace that

HOWEVER in looking at the fuse box today I find a single grey wire coming over the top from the rear, into a plastic foot with a footprint like a relay, with the 3 other spades being plastic blades

only seems to go in one posn ( top row left of centre ) and everything seems to be working

BUT what was this for?
 

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Hi Chris, I'm working on a duff rear fog at the mo and from my reading of the Brooklands wiring diagrams if front and rear lights are fitted then there needs to be a relay in 10 instead of a link pin on account of the increased current. That wire would have been in 10 like my 1995 and the photo in your post.

pete
 

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Yes in my 95 caravelle the grey wire with black plastic foot is in ten,sorry dont know what its for.
 

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Discussion Starter #8
getting desparate now - 1994 T4 Caravelle - rear fog only as standard - 2 posn rocker switch on dash - strange grey wire with plastic foot and single male blade was I seem to recall orignally in relay posn 10, and where i can find any redundant bridge in my odd and sods box!

so

removed relay - didn't originally have brass bridge as far as I can remember

replaced fuse

new rear bulb just in case

light switch off

fog light switch off

1. turned on both switches, through each setting position

fog light telltale doesnt illuminate ( but night time icon illumination does work )

rear fog doesnt work

fuse is fine

2. turned it all off and replaced relay

turn light switch on to side light

turn fog light switch to first position ( front ) and fuse blows

- so a short in the front loom to the front lights? or in the lights themselves ? ???????????? ( belly pan has been off, a wire might have been crushed?)

- but why doesn't rear light illuminate under (1) above ? is it because I dont have a bridge in place?

3. put the plastic footy thingy in, and the blade picks up the 9 0'clock posn on where i think terminal 87 ( live out?) would sit - fuse blows as soon as front fog switch on (side lights already on )


- how can I at least get rear working again for safety, and MoT

seems to me that without bridge or relay, no power is getting to the switch under sitn 2 as above?
 

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Discussion Starter #9
Re: Fuse Box (1994) - loose wire in front side

ok fixed it

for the benefit of others... unlike traditional use of a relay, in this case the relay if used is on the battery side of the fog light switch, and which it feeds via a fused feed, in a couple of manners dependant on whether just rear or front an rear fogs, and age of vechile

thanks to DavieT4 for his wiring diagram, part 30 here

http://www.vwt4forum.co.uk/showthread.php?t=6891&highlight=wiring+diagram&page=3

so on the relay panel, posn 10 ;
early models have a grey wire with plastic foot and single blade in to slot 1 - that wire is a live feed when main lights on
later models have brass bridge from slot 4 - an ignition live feed - to slot 1
slot 1 in each case feeds to the fog light switch

that switch at first click feeds front fogs DIRECT, at second switch, front & rears,

the relay when substitued at posn 10 picks up a side lights live feed at slot 3 to energise the relay, which then takes ignition live power from slot 4 and passes to slot 1 and hence to the fog light switch

so the relay is not being used to protect the switch

my fault has been a short in the front lights loom ( probably where belly pan removed and refitted ? ) so having now undestood the route the power takes, and why a short in front can stop rear fog working, I have isolated the front fogs with an in line bullet concector joint under the bonnet where new loom comes through the firewall, by temporarily disconnecting it; rear fog works alone again now - safe and legal!

next job to test continutity in the front loom !

the above 1.grey wire and 2.brass brigde and 3.relay options should mean that the rear fogs work....
1) with main lights
2) with ignition on
3) with side lights on
 
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