Jump to content

Headlight Wiring


Recommended Posts

This is now officially doing my head in!

Used a universal wiring loom on my A series as the original was toast, and I'll be damned if I can get the headlights working.

I have the switch, relay and headlights all wired in. Sidelights work perfectly, headlights don't.

In a nutshell, I have the headlight switch wired to the relay, with switched live wires. When the switch is on, power goes to the relay on the wire from switch. With ignition on, power goes to the other side of the relay. This should close the relay, sending power from the other switched live to the headlights and lighting them up.

Except nothing happens. If I bypass the relay and wire lights straight to either the headlight switch wire, or the switched live (the wire the relay should connect it to), they come on.

My meter shows the connection being made between the switched live and headlight wire when both switch and ignition are on, but the headlights don't come on.

Given the meter shows the connection apparently being made, surely that means the relay is ok? (I've tried 3, all new)

Engine turns over on ignition and fuel pump, which runs off switched live as well, runs.

If it wasn't obvious before, I'll mention I have zero prior experience in car electrics!

As if that wasn't obscure enough, my hazards lights work, but indicators don't...

Link to comment
Share on other sites

To operate the relay you need power to one side and an earth at the other, sounds like your sending power to both sides (which won't switch the relay)

Here's a diagram i drew for wiring in spotlamps for someone, but the basics are the same.


The 'Full beam take off' is the power wire from the light switch, the other side goes to an earth.

A nice fresh power feed from the battery/ or alternator, fused near to the power source runs to the relay

When the relay is switched the power runs through the relay and out to the lamp

With it wired up as above you should hear the relay click/close when you turn the headlight switch on.

Link to comment
Share on other sites

Cheers, works perfectly now. Cut second wire from switched power and connected to earth and all is well. I am wondering why the hell the loom makers connected two lives and no earth to the relays tho. Mind you, some of the wire colours were different, have extra wires some places and not enough others so should come as no surprise....

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...