Advice-adding driving lamps to car

Vlad_Dracul · 07-08-2008, 12:34

Hi all,
I know the usual method is to use a relay,use the high beam switched 12v to operate a relay coil and draw a supply via a fuse from the battery to the lights

BUT

the car in question has weird/different wiring.

It has the usual halogen H3 type headlamp bulbs but on checking with a test meter,even when the lights are off,there is +12v available at the headlamp connectors.

How does this work and how do i connect my realy? would i just connect the coil in parallel with the high beam bulb? that sounds logical. I dont have the car with me to try at present.

Its a Vauxhall Agila which i think is a corsa variant

ta

**Rob** · 07-08-2008, 12:41

I'd find yourself a Haynes Manual. They have wiring diagrams in them that should show you what is what.

**Kymmy** · 07-08-2008, 12:44

It's a switched earth then, Instead of battery going to switch then to bulb and finally to earth it has battery going to bulb then to switch and finally to earth. If you want to add a relay for more lighting it needs to go in after the switch

Vlad_Dracul · 07-08-2008, 13:05

There is no Haynes manual for this specific vehicle and the Corsa manual doesnt mentuion it as a variant.

As Kymmy says- i too had it as a switched earth system. At one point i found an output from the lighting stalk switch which had +12v on it when the main beam was switched on and 0v on it when off. I thought that was the one howver on putting the ign key in,a different condition existed,,,arrghh

**Kymmy** · 07-08-2008, 13:38

You've got to remember that most modern cars/bikes already have lighting relays especially with the advent of HID's that need one hell of a start up current..