Electrical gremlins - tail lights not working - BH9

[swamp]

Hey guys I’m chasing electrical gremlins with no luck thus far. 
 

my tail lights do not work. The brake lights do, so do the number plate bulbs that run off the same circuit as the tail lights. 
 

I did have a leak in the tailgate centre garnish, so siliconed it up. The bulb holders got a bit corroded so I got in there with a rotary tool and replaced one that was Too far gone. New bulbs too, but the old ones still work. 
 

my car was recently stolen and recovered, I haven’t tested the light switch which could’ve been damaged? But they did wreck the column and the park light switch that sits atop it. I haven’t tested this circuit but I have managed to press the switch against its contacts and made the relay click but haven’t seen the lights come on. 
 

Ive found that the tail light power wire has >1 volt at the connector at the rear. This is also the same at the connector behind the under-dash fuse box. 
 

I’ve checked all relays - not properly but can hear em click - and my fuses are working. But I need some advice as I’m missing something.. 

 

 

 

Edited November 28, 2023 by swamp

[Gripless]

Are you testing with all bulbs removed on the tail lights? Maybe one side has a short or corroded. If you can test at the plugs under or near the rear seats. That may tell you if the issue is at the front or rear of the car. If you have voltage there then the issue isn’t the switch or fuse box damage.
 

WI-12

check

relay for tail & illumination

fuse 12

two V wires on a1 b2

Wire WG on D12

 

1v on a digital multimeter could be a faulty relay as it’s an average reading over maybe 0.5 seconds.

If a relay is very rapidly connecting and disconnecting the average can be a low voltage.

Analog meters or oscilloscope you can se the voltage swing around

 

the other option is something is grounding that out and your multimeter is only seeing some of the voltage.

 

you can test a relay with a 9v battery in many cases outside the car.

 

 

 

[swamp]

Thanks for your reply @Gripless

 

I’ve tested it with all the bulbs in after checking that each bulb/holder works. 
 

Yesterday I hooked up the +/- of each bulb to a battery to test and they all worked. 
 

ive checked the rear plug and the one under the dash, the wire at both plugs show the same result. So thus there isn’t any voltage from the front. 
 

I really think it’s an issue with the switch. Or relay as you suggest. 
it could also be the park light switch on top of the column, perhaps that needs to be connected to complete the circuits. 
 

I don’t know which relay it is Lol, I’ll go over the diagrams with fresh eyes. 

 

Are you testing with all bulbs removed on the tail lights? Maybe one side has a short or corroded. If you can test at the plugs under or near the rear seats. That may tell you if the issue is at the front or rear of the car. If you have voltage there then the issue isn’t the switch or fuse box damage.

[Gripless]

Relay is likely next to fuse box and lots of relays are the same so you can borrow another one for testing.

 

[swamp]

After much head scratching, trying different things and sometimes same things over and over, I’ve solved this problem! 
 

it didn’t help that the wiring diagrams - I’ve seen about three different sources - are have different wiring colours and don’t have repair/troubleshoot procedures. Meaning that I’ve had to puzzle together what info they’ve given and combine that with past knowledge and experience which isn’t that extensive. 
 

I saw this video at the start of the day, and thought I’d perhaps test this out if all fails. Because I was 90% certain that the tail lights can operate without the park light switch. 

my wires were orange and white with green stripe. 

[THUNDA]

16 hours ago, swamp said:

After much head scratching, trying different things and sometimes same things over and over, I’ve solved this problem! 
 

it didn’t help that the wiring diagrams - I’ve seen about three different sources - are have different wiring colours and don’t have repair/troubleshoot procedures. Meaning that I’ve had to puzzle together what info they’ve given and combine that with past knowledge and experience which isn’t that extensive. 
 

I saw this video at the start of the day, and thought I’d perhaps test this out if all fails. Because I was 90% certain that the tail lights can operate without the park light switch. 

my wires were orange and white with green stripe. 

so was it a faulty park light switch? 

[swamp]

@THUNDA my car had been stolen and they had broken the tabs the switch fits in.