LED Bar Relay Question

[PapaDragon]

I fitted an LED light bar to my 99 2.7i

Originally had the live and neutral coming straight from the wires that supply the headlamp brights, and it worked perfectly, came on only when Brights were on.

I then fitted a switch, and relay. and used the same live from the headlamp bright to switch the relay. The bar now comes on when the lights are on, either dim or bright...

Any ideas, before I take it to a sparky?
Thanks!!

[JAMES399]

When the dim lights are on, I think that some voltage is feeding back from the dim filament through the bright filament to the relay coil. Usually relays will trigger at a lower than rated voltage. This feedback voltage won't be high enough to light the bright filament, but probably is enough to trigger the relay.You can verify the voltage by connecting a VOM between the low beam and high beam connectors when the dims are on. If this voltage is there,
try installing a diode to block the voltage through the bright filament to the relay when the dims are on. Observe diode polarity. The diode will pass voltage when the brights are on. See diagram.

The yellow line represents the feedback voltage when the dims are on . Use a 1N4001 or 1N4004 diode. Readily available at most electronics stores.

- 399

[pietpetoors]

Or you can use a relay with the switch. Tap the supply to relay coil from the bright + in James' sketch and cut the earth with the switch.
Brights + Leg 85
Earth to switch, from switch to 86
Battery + to 87 with fuse close to battery.
30 to LED bar +
Earth lead bar on body or directly on battery.