Strange electrical phenomena

[ColinJack]

I have an 'interesting' wiring fault.
Mk3 ...
MOT man pointed out that when the lights and hazards are on together the number plate light at the rear also flashes in time with the hazards.

Faulty earth maybe?

I'm no auto spark but can do most stuff. I wondered whether anybody here may be able to point me in the right direction to resolve this?

Thanks.

[Jas278]

Earth check first id say ,

[MinorMatt]

I take it that it failed because of it?

Its not a common issue but as Jas says it will almost certainly be an earth fault. The clusters earth at a bolt inside the van just above the cluster... I can't think off hand where the number plate lights earth - but probably the same place

[ColinJack]

I take it that it failed because of it?

Its not a common issue but as Jas says it will almost certainly be an earth fault. The clusters earth at a bolt inside the van just above the cluster... I can't think off hand where the number plate lights earth - but probably the same place

Thanks Matt,

That was my first guess - indictor lights earthing back through the number plate light.
Will take the cluster off and have a poke about.

[MinorMatt]

Its unlikely, but I would also take the rear clusters out and inspect the bulb holders/tracks and see if there is any corrosion/grot etc which is tracking across the conductors

[ColinJack]

Its unlikely, but I would also take the rear clusters out and inspect the bulb holders/tracks and see if there is any corrosion/grot etc which is tracking across the conductors

Interesting thing is that it only happens with the hazards - not the indicators individually on their own.
Will pull out the clusters and take a good look.

[ColinJack]

Its unlikely, but I would also take the rear clusters out and inspect the bulb holders/tracks and see if there is any corrosion/grot etc which is tracking across the conductors

Am I correct that the Mk3 Mk4 and Mk5 all have the same rear clusters - lens and bulb holders?

[ColinJack]

I think I have solved the mystery.
Checked all the usual suspects - earth, frayed cable etc, to no avail.
Then thought about it and replaced the LED bulbs in the numberplate lights with standard 501s. Problem went away!
Seems the LED lights were either picking up RF or were very sensitive to the momentary drop in voltage when the hazards flashed.
Interesting one.

[Noctule]

You should've mentioned the LEDs earlier.

Just lately I've seen quite a few odd lighting issues on a variety of vehicles , all presumably caused by cheap LED replacements. Most were sidelights and number plate lights, some on Transits, all giving off 'warp-drive' lighting effects rather than steady lights or just flashing randomly in the dark.

Dump the LEDs and just buy good quality bulbs.

Mat

[ColinJack]

You should've mentioned the LEDs earlier.

Just lately I've seen quite a few odd lighting issues on a variety of vehicles , all presumably caused by cheap LED replacements. Most were sidelights and number plate lights, some on Transits, all giving off 'warp-drive' lighting effects rather than steady lights or just flashing randomly in the dark.

Dump the LEDs and just buy good quality bulbs.

Mat

Yes. Hadn't occurred to to me. Have already replaced the bulbs with Lucas.