Aftermarket H4 harness wiring?

[Geneman]

happy Easter peeps. or whatever you celebrate,.

adding amber headlights to my race car so must add the harness + relays etc.. (online they are literally 15-25 bucks!)

its very straighforward except the three prong lead that goes to the " existing car harness". i do not have one. so what do these three leads go to?

its a blue , white, black plug. seems the black is ground. but if i hook up and then try to trigger lights by crossing the other pins to the black ( or each other). nothing happens!

so is the switch /harness in the car providing a 12 volt signal to the relays? even though the rest of harness gets 12v from the other hioookups?

so one prong must be high, one low. then ground i guess.

[Arne2]

Relays need power from 2 sources. The main power from the battery to supply power to the lights when the relay is activated, and switched power to trigger the relay.

The harness you are using is designed to connect to a car's existing headlight system, which you don't have. You need to provide 12v to the white or blue pins to trigger the relays.

[Geneman]

Fantastic. Thank you . Makes total sense now! Bless you. Frank

[Geneman]

Arne. So the ground is shared by both relays?

[Arne2]

If your harness is the same as pictured, you may need to connect a ground to the black pin as well. The relays look to have a metal case though, so they could be self-grounded.