New wiring for 77 headlights--fried one set of wires

[mtnman210]

I'm trying to wire up the headlights on the trail rig. It still has the original 77 round headlights. And was activated by the knob on the dash and the hi/low switch on the floor. That is all gone. my plan is to put the hi beams on a toggle and the low beams on a toggle. I've got 2 toggle switches and 2 relays.

on the back of the headlight are 3 posts. I'm assuming that one is ground, one is low and one is high beam. Would this be correct? and if so I would just wire the corresponding switch to the correct post on the headlight?

 

[frankin5]

you assume correctly.

 

[mtnman210]

sounds good. I guess it's garage time.

 

[dyeager535]

I'm thinking you need a relay for both, or you'll burn the switches out in short order. Makings of a fire.

 

[dremu]

Dorian's right, but for another reason as well.

Even if the switch is capable of carrying the juice -- a 20A switch oughta do it -- that's still a lotta heavy wire to run, from the battery to the switch back to the lights.

Ideally you'd run a short wire from the battery to the lights, with a relay in it, and then you can use light gauge wire from the switch to the relay. Benefits are that the switch doesn't carry but a fraction of an amp, and you get more voltage to the lights so they're brighter.

Check out my thread on this ... the idea there was to get brighter lights, but it's the same for you running new wire.

-- A

 

[smalltruckbigcid]

Well thats almost right on the posts. The low beam should have 3 and the high should have 2 posts.

So here's how this works. On the low beam one post is ground and it will also have a jumper wire to one of the posts on the high beam, either one will work.
The second post will be the brighter side of the low beam. It will only have one wire on it from your toggle or relay. The 3rd post on the low is the dim side of the low beam and it will also jump top the other unused post on the high beam.

So whats happens when you turn on the low beam side is the brighte side of the low comes on. Then for high beams you throw the second switch and and turn off the low beam switch and the headlights switch to high beam and all four work as planned. The high work as normal and the low are switched to the dim side of the bulb internally.

If you wire it to 2 switches and don't shut off power to the bright side of the low beam then it will probably overheat and shorten the life on those 2 bulbs.

Hope this helps.

 

[dremu]

Well thats almost right on the posts. The low beam should have 3 and the high should have 2 posts.

So here's how this works. On the low beam one post is ground and it will also have a jumper wire to one of the posts on the high beam, either one will work.
The second post will be the brighter side of the low beam. It will only have one wire on it from your toggle or relay. The 3rd post on the low is the dim side of the low beam and it will also jump top the other unused post on the high beam.

So whats happens when you turn on the low beam side is the brighte side of the low comes on. Then for high beams you throw the second switch and and turn off the low beam switch and the headlights switch to high beam and all four work as planned. The high work as normal and the low are switched to the dim side of the bulb internally.

If you wire it to 2 switches and don't shut off power to the bright side of the low beam then it will probably overheat and shorten the life on those 2 bulbs.

Hope this helps.

Eh? The '77 has the round headlights which have three terminals, period... you must be talking about one of them newfangled later trucks, like maybe with the square headlights?

Or are you talking about quad headlights like for 89-91?

-- A

 

[smalltruckbigcid]

Brain fade on a very bad day. Thats for a four headlight setup. On a single headlight setup its different.

Like I said a very bad day...almost told the boss I quit last nite and was still so pissed this morning I called in sick

 

[mtnman210]

I changed plans a little and ended up using some aftermarket lights and ran into a problem.

I'm using these now. instead of 3 posts there are 3 tiny wires coming out of the light

ok I followed the same installation pattern as when I did the relays for the fan(what posts go to what device). and when I flip the switch I get no head lights then I melted the connector between the wire from the relay to the wire going into the headlight.

The wires that go into the headlight itself are really tiny and thats what melted. Should I try and rebuild the light with heavier gauge wire or are my problems elsewhere? I could also go back to the stock headlights. I just need to find clips big enough for the posts.