Towbar electrical gremlins

[marshian70]

Hoping for some advice
Taking cali away next week with our Atera bike rack. Connected the rack this morning and only one brake light (the left one) working, everything else seems OK.
Checked bulb - that's fine. Tried another light board and the same issue, therefore I assume the problem is the van.
I'd check the fuse next if I had any idea which one and where it is?
Any ideas? The towbar is a Thule unit which was already on the van when I purchased it.
Cheers all

 

[Alan Andrews]

Hoping for some advice
Taking cali away next week with our Atera bike rack. Connected the rack this morning and only one brake light (the left one) working, everything else seems OK.
Checked bulb - that's fine. Tried another light board and the same issue, therefore I assume the problem is the van.
I'd check the fuse next if I had any idea which one and where it is?
Any ideas? The towbar is a Thule unit which was already on the van when I purchased it.
Cheers all

If you are saying that only one light works when you connect the tow light board, but the van lights are all good, then suggests that the issue is with the light board or the tow bar connector.

Do you have 7 pin or 13 pin connector?

If only one light when without the light board plugged in to connector, then the issue is the van wiring. Pop the light housing and try a different bulb. Is going to be a twin element bulb.

Use a electrical meter to confirm that you see 12v when the brake peddle is pushed down.

 

[OGII]

More likely a loose connection in the van electric socket. Usually simple enough to check.

 

[marshian70]

Cheers, van lights all OK. Tried wiggling the connector but makes no difference. Both light boards produce the same results - van OK but right brake light not working so assume it must be the van tow bar wiring, which I assume is separate to the van lights themselves. I'll take a look at the tow bar van socket cheers

 

[Alan Andrews]

Cheers, van lights all OK. Tried wiggling the connector but makes no difference. Both light boards produce the same results - van OK but right brake light not working so assume it must be the van tow bar wiring, which I assume is separate to the van lights themselves. I'll take a look at the tow bar van socket cheers

The standard wiring arrangement for both a 7 pin and 13 pin connector, only provides one pin for the brake lights.

So if one brake light does work when the board is plugged in, then the van and the towbar connector are likely to be good.

The problem must therefore be in the board wiring itself.

Remove and change each tail/brake light bulb. Do not rely on a simple look to see if you can see a break in the filament.

As I have said, these bulbs are the twin filament type.

Has someone changed the bulb to be single filament only?

Does the tail light work on both sides?

Also check the earth connections associated with the board lights.

For reference here are the standard wiring diagrams for 7 pin and 13 pin towbar electrics:

Towbar Wiring Guides : Electrical Wiring Guide for Towbars : Watling Engineers UK

www.watling-towbars.co.uk

Wiring diagram for a 13 pin tow bar socket and plug

 

[marshian70]

The standard wiring arrangement for both a 7 pin and 13 pin connector, only provides one pin for the brake lights.

So if one brake light does work when the board is plugged in, then the van and the towbar connector are likely to be good.

The problem must therefore be in the board wiring itself.

Remove and change each tail/brake light bulb. Do not rely on a simple look to see if you can see a break in the filament.

As I have said, these bulbs are the twin filament type.

Has someone changed the bulb to be single filament only?

Does the tail light work on both sides?

Also check the earth connections associated with the board lights.

For reference here are the standard wiring diagrams for 7 pin and 13 pin towbar electrics:

Towbar Wiring Guides : Electrical Wiring Guide for Towbars : Watling Engineers UK

www.watling-towbars.co.uk

Wiring diagram for a 13 pin tow bar socket and plug

Thank-you. All sorted.- bit of confusion from my assistant who told me the brake light was not the one it actually is! Anyway long story short it’s working. Thanks for the assistance!