My reverse lights aren't working - bulbs are fine and voltage is getting through on the light green wire from the shifter switch, but as soon as the bulbs are inserted the voltage goes to zero. Is this a short?
I ran a wire directly from the battery to the tail light circuit at the bulb connectors (one of the light green wires has been stripped and taped from a previous diag I'm guessing), and both bulbs lit fine... I then tried the same thing from the dark blue wire on the shifter switch connector - got battery voltage but as soon as the wire is connected to the harness (bulbs inserted) again the voltage goes to zero.
Turn fuse is fine and turn signals work fine. Am I right in saying this is probably a short between the blinker unit and the shifter switch?
I hope not... don't feel like ripping all the center console out to chase this one down. PITA...

Cheers,
Stu

 

Weird
If you had a direct short on the blue ( supply to switch ) you would not be getting 12V or the turn / backup fuse would be blowing.
I would have said you have a ground / back feed problem typical of the shared bulb setup GM uses but the fact you can make them work by applying power direct to the bulb negates that.
Possibly a bad connection on the blue somewhere showing power but not enough passing under load when the bulbs are installed?
Put a bulb on the blue wire at switch and see what happens?

 

I concur. It does sound like a high-resistance contact somewhere.
As vetteoz suggested, I would use a bulb to test the power on the blue wire. If it does not light but shows 12V, I'd go after the connector on the turn signal flasher or the shifter connector itself.

Let us know what you find.
Lou

 

Did as you both suggest and the test bulb doesn't light. So what does this mean?
Btw tested with connector unplugged.

So probably need to run a new wire?

 

Btw can you explain this further please?

 

Faulty connection on the blue wire somewhere
Simplest fix would be to run a new wire to the switch from any convenient fused 12V source
Proper way would be to located the feed wire to the flasher unit and rewire from that ( assuming your fault is between the flasher supply and the switch which it appears to be)

 

Turned out to be one of those frustrating phantom "there's nothing wrong" problems. Took out the centre console, lifted the carpet and pulled the wiring out - there's actually already new wiring (red) going to the light green and dark blue wires which looks like it's either from the RHD conversion, or there's been a problem with the reverse lights before and a previous owner has run new wiring.

Anyway, I retested the dark blue wire with a globe once I had it out from under the carpet, and it worked fine... what the? Checked along the wiring for any splits etc, all good. What the?
So I resoldered the connections anyway and put it all back together and the lights are working fine now.

Which is good, because the wiring behind the centre console is a complete mess. The flasher unit has been relocated there too and is basically inaccessible. If I had to run a new wire I'd probably do it from the back of the fuse box.

Thanks for your help