Headlight harness upgrade and modification to 4 highbeams

[MadOgre]

Just use an off the shelf Bosch 4 or 5 pin relay. Get them with a mounting tab - it makes the job so much easier:

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Control wiring is on 85/86 and the load is across 30/87.

Advance has a 40 amp general purpose relay from Optronics that does the same thing - for $5.49:

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Ah cool. So what is the 87a for ? Any suggestions on weather proofing it ?

 

[MadOgre]

Im guessing for left and right ?

 

[chengny]

30 to 87a is normally closed and opens when the coil is energized. 30 to 87 is normally open and closes when the coil is energized.

You would use 87a to provide power to a component when the control switch is off (i.e not keeping the relay pulled in). Another use would be if you had two components in the same circuit that were not meant to be on at the same time. Maybe like daytime running lights:

87a to the daytime lights

87 to the normal headlights

Battery power - always in on 30.

Headlight switch off - coil is de-energized. Power in at 30 and out on 87a. Daytime runners ON.

Pull the headlight switch out and coil pulls in, opens 30/87a and closes 30/87. Daytimes go off and headlights come on.


85 and 86 are the coil terminals and are only part of the control circuit. When an amp rating is given for a relay it always refers to the current carrying capacity across 30 to 87/87a.

 

[MadOgre]

Thanks chengny

 

[flyboy1100]

Cool link Thanks. Seems after reading that, its maybe not a bad idea to pick up the upgraded wiring kit like the one from lmc ?

i already have relays and wires on hand and will build my own harness

 

[flyboy1100]

Im not sure where a good place would be to find the right relays, on there own ?

I have bad luck with parts guys. I usually end up getting mad at them and then having to show them where to find it in there own books.

digikey. i bought a few relays a while ago for the purpose of doing my motorcycle, and have to have a few on hand, i spent about 3.50 shipped per relay.

 

[flyboy1100]

Ah cool. So what is the 87a for ? Any suggestions on weather proofing it ?

i should have just multi quoted a single post...

87 is the switched output, 87a is the unswitched. IE the relay has not been activated, current will flow from 30 -> 87a, but the relay is active it will flow from 30 -> 87. they are useful when you want to turn something off when turning something else on.