Wiring Route to Brake Lights - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 4 (permalink) Old 06-23-2018, 10:39 AM Thread Starter
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Location: Shoreham-by-sea, West Sussex, UK
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Wiring Route to Brake Lights

Yesterday, I returned to my car to find a flat battery - a 1975 RHD GTV

I traced the problem to the brake lights remaining on dimly when the car is standing. I'm getting a permanent 2 volts on the feed to the lights, 12 volts, if I disconnect the rear lamps. The brake lights work fine when the pedal is pressed

The brake switch seems OK - no continuity unless pressed. The 12 volt feed to the switch is OK - comes from the fuse box and is live without ignition. I get continuity between the 2 wires on the switch when they are disconnected - which can't be right.

So I figure, some kind of short circuit to +12v, but not a dead short, as the voltage drops when the lamps are connected - and they only glow dimly - so must be passing through something with high resistance. Any thoughts?

Anyone know the route the wire takes to the rear lamps - I've traced it to a grommet from the boot - not sure if that goes under the rear seat or under the floor. My wiring diagram shows a multi way connector block somewhere.

I could run a new wire, but that's almost the length of the car!

My reversing lamps aren't working - not sure if that is relevant- another thing for me to check though.

1975 GT Junior with 2 litre lump
2006 Subaru Impreza WRX
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post #2 of 4 (permalink) Old 06-24-2018, 03:55 AM
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Hi @malcolm1
As you've discovered, there are two brake light switches in your Jr. I'd disconnect the wires on the rear switch and check the resistance across the switch terminals. It should, of course, be infinity with the brakes released. Do the symptoms disappear with the rear switch disconnected? If so, you could then leave only one wire connected to the switch and tape up the loose wire until the switch gets replaced.

Jim

Series 2 USA 1750 GTV (in Series 1 European clothing)
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post #3 of 4 (permalink) Old 06-24-2018, 05:16 AM
The multi plug wire is right up under the dash (on LHD cars it is near the windshield washer sqirter). The harness (at least for LHD) goes along the floor, up the rear arch and through the rear seat back and then follows along the top of the wheel arch until it reappears between the rear valance inner and outer sheet metal. If you haven't already, ask @papajam for a wire diagram.

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post #4 of 4 (permalink) Old 06-24-2018, 07:29 AM Thread Starter
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Thanks all, yes in parallel found out about the 2nd pressure switch at the rear on RHD standing pedal cars - on the brake biaser.

This switch seems to be the cause of the problem. I have disconnected it and taped up the wires. The brake lights work normally now and the lamp glow when the car is standing has gone.

I have ordered a replacement switch from Classic Alfa (8.50)

1975 GT Junior with 2 litre lump
2006 Subaru Impreza WRX
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brake lights, continuously, illuminated

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