How and where to mount H4 light relays

[Kevin Lewis]

Is there anyone out there who has mounted relays after installing H4's with 100 watt bulbs. Need mounting instructions for the wires and placement, near light or under dash near fuse block? I have a 1972 914-4 1.7L is that makes any difference. I am tired of being in the dark, but don't want to burn up my light switch.

[Acox914]

100 watt low beams?


or 55/100's?

do you really need a relay for them?

[Kevin Lewis]

They are 80/100 W bulbs and I was told to install the relays to mitigate any fuse or wire problems.

[Dave at Pelican Parts]

Put them near the headlights. You'll probably want two relays; one for high beams and one for lows. (80W is quite a bit more than the stock lights.) You will need to run a single large wire to the relays--I would run it direct from the battery with an in-line fuse near the battery. It's a bit of a pain running the wire along the main harness, but it is doable. You might run it from the fuse panel if you think that won't cause problems. (I wouldn't, though.)

Assuming the relays have standard Bosch numbering, you hook up 30 to the battery wire. You hook 87 to the light, and daisy-chain to the other light. You hook 85 to ground, and hook 86 to the old wire that used to run directly to the light.

--DD