headlight relay

I am trying to find a wiring diagram to install a 12 v 30 amp relay for my headlight using the stock wiring in my
headlight shell.The blue-white wire to the 2 position light switch looks to be the main power from the master
switch.From there I am at a loss of where to go next.Is the relay polarity sensitive as far as hooking up the ground
74 Roadster ,stock wiring,positiive ground.I tried to search,but came up empty.My relay has markings of 30,85,86,
and 87.Any help would be appreciated.
Ying

The wire from main switch is blue yellow not blue-white.Sorry for that typo
Ying

I'm not sure you can relay with the factory crisscrossed wiring and triple swithces Hi-Low-Flash. It took me 3 compact 1/2 size relays to get it done in Peel inside the headlight. I had to just think about the switching connections before I got to the actual bulb power wires. Relays are not DC polarity sensitive. Really only need the hi beam as no matter how good the low beam works its mostly a marker light for traffic not much for lighting road at any speed.

YING said:

I am trying to find a wiring diagram to install a 12 v 30 amp relay for my headlight using the stock wiring in my
headlight shell.The blue-white wire to the 2 position light switch looks to be the main power from the master
switch.From there I am at a loss of where to go next.Is the relay polarity sensitive as far as hooking up the ground
74 Roadster ,stock wiring,positiive ground.I tried to search,but came up empty.My relay has markings of 30,85,86,
and 87.Any help would be appreciated.
Ying

Click to expand...

Run a power wire from the battery, use two relays, one dip/low, one main/high. Use the existing wire going to the headlamp to activate the coil on the relays.

You will need two relays, one for dip and one for main beam. The two wires that normally go to the headlight bulb go to 86 (one on each relay) 85 goes to earth (x2), run a fat wire (black) from the negative side of the battery to the 30 terminal and piggyback it to the 30 terminal of the second relay, connect 87 to your headlight bub ie one from each relay to dip and main beam. It's well worth running an equally fat red wire from the earth of your headlight bulb to the +ve side of the battery. You can connect terminal 85 to this return wire.
A 60watt headlight bulb draws 5amps at 12 volts so a 30 amp relay is overkill, look for micro relays they fit neatly inside the headlight shell and use heat shrink sleeving on all the spade terminals

+1 Stuff everything in the headlight shell. Nice and clean and dry in there. It rains a lot where I live..