Electric Gremlins….One brake light not functioning

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Apr 13, 2023
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Hi All

So today I tinkered with the buss replacing the rear light seals and putting on the original red lenses.

Long and short in the process of doing so I’ve managed to wipe out my hazards and rear right (as you look at it) break light.

Findings along the way:

- the left hand light cluster (as you look at it) appears to have a non factory ground wire running from the chassis to the back of the bottom light cluster bolt with a ring terminal and a small bolt.
This feels like a kooky set up so believe it may be a cause as unless you know it’s there you can’t remove the light cluster. It was obviously finger tight as it dropped off when removing.

- on re installing the earth wire and trying the side lamps and indicators it was upsetting the indicator and it would flash quick. At this point hazards still worked.

- I slackened of the screw then retightened it holding the bolt tighter essentially nipping it up former. This seemed to of rectified the indicator issue as it now blinks at regular speed however I now have no brake light on the opposite side (right hand side without an earth wire)

- It was at this point I retried the hazard switch and nothing not illuminated switch and nothing at the back so believe the relay has been fried.

Reason I assume this is I fried the relay early on when I had the dash pod out and it had the same symptoms (replaced and it wasn’t an issue.

In the main the wiring is fairly unmolested but clearly has a gremlin which I believe is back of the bus now as I was have having an issue with hot fuses in the past and cleaned up the fuse board and connections at the dash pod end and front lights and it was mainly 95% original wiring and in good nick.

Electrical knowledge and diagnosing isn’t so great…..I should of just not tinkered with it 😂

Any ideas?
First check the spade terminal on the brake light, they do corrode/ come loose. After that try an earth wire on lamp. Have you tried a new bulb?
I presume you didn't disconnect the battery before starting work?
It appears that a previous owner may have had problems by installing an additional ground.
Have you swapped the bulbs round to check that's not the issue?
67 Panel.
- Il get out in the garage tomorrow to check the spade terminal (could of been missed as not visible when I took the cluster out as it appears it has a snug rubber boot on the wires)
- Bulb is fine as it illuminates when I put my side lights on

- the additional ground would this insinuate there’s a break in the black wire somewhere in the rear light loom?
- I didn’t disconnect the battery…rookie mistake can’t say I really thought about it as didn’t plan to remove any wires etc just old seals and lens.
2 filaments in that bulb, one for side and one for brake(and indicator if it is still wired as US) so check the bulb first
Bad earths cause havoc with electrics especially lights. My engine kept running with the key removed until I took my foot off the brake. It was a bad earth on the tail light!!
2 filaments in that bulb, one for side and one for brake(and indicator if it is still wired as US) so check the bulb first
It’s been converted by the look of it as it runs two bulbs in each light rather than the single bulb US Spec.

Top - indicator light
Bottom - side light/brake light

As part of identifying the working gremlin I’m swapping out the old lamp holders the the better spec with direct connections in the back of it (unlike the repro ones in it that are knackered with wires leading to spade terminals that are more enclosed)
Any ideas which wiring diagram to follow as 68 isn’t correct due to the conversion.
Plan to get at it tomorrow evening/Wednesday
You need a test lamp, you can make your own from old bulb holder, 2 bits of wire and some small croc clips.
So got out in the garage day to tackle it and replace the old poor quality repro light housings for new top quality ones and figure out the wiring issue….so shiny!


- only one of the lamp holders had a visible earth bolted onto the back of the screw holding the lamp assembly in (which to me was a bit suss) both new units have a cast ground point so guessing both should be grounded?

-wiring on the culprit side was done through spade connections and a couple of these were seriously corroded. All terminals replaced for OEM crimp style and heat shrink insulation added (very therapeutic job) and look a million time better than the cheap plastic crimp connection.

- Earth point added to the second light.

- Main battery earth point cleaned up it was a bit tarnished

I now have break lights, indicators, and side lights working on both sides. My fuel guage needle now doesn’t tick in time with the indicator 😂
I’m guessing cleaning everything up and adding a ground could of solved a few gremlins.

Only issue left is the hazards not working.

On pulling the knob the indicator bulbs illuminate in the dash but the knob doesn't illuminate, it doesn’t tick, and doesn’t work.
I’m guessing I may of frazzled the relay? As it did this when I first got the van and I remember similar symptoms.

Il get out the one evening and replay the relay to see if that fixes it but definitely took a few steps forwards.

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