four headlight truck?????low/high beams

[yevgenievich]

89-91 headlights are wired using smaller wiring and splits. But I had a case where I was using 89-91 harness on an 85 truck with regular set of 4 headlights and it became with low beam off when high beam is selected. Did not get a chance to ever install relays.

 

[charlesg]

Yours seem to be split and not set up for four lights to be on. What year is it? The best way would probably to install relays to trigger from headlight switch and wire the lights to be on with high beam. But on regular 88 and earlier four headlight set up there is a green wire and brown wire connecting to low beam light. It lights up differently with high vs low

My truck is a 91

 

[yevgenievich]

My truck is a 91

Then it is correct factory operation. If you want low to stay on then need to run relays for the headlights and use a diode to feed the low beam relay from the high beam control wire.

 

[hawk630]

I really like your headlight schematic. Do you have any more of the wiring.

1985 truck with 91 electric doors

Rick near Seattle

 

[73c20jim]

Go to Reference section. All the wiring diagrams you'll ever need.

 

[charlesg]

question, I got a relay but it has a 87a plug, along with the others, can I still use it??

 

[yevgenievich]

Yes, the terminal is just not used if not needed.

question, I got a relay but it has a 87a plug, along with the others, can I still use it??

 

[charlesg]

Yes, the terminal is just not used if not needed.

Thank you!!!!

 

[Daveo91Burb]

Then it is correct factory operation. If you want low to stay on then need to run relays for the headlights and use a diode to feed the low beam relay from the high beam control wire.

Do you need to use a diode? I've had mine wired for years with just using a relay in between lows and highs - when highs are on, relay is triggered to feed the lows. When just the lows are on, relay acts as just an open switch. It's worked well for a couple of years, no diodes to mess with. I DID use the diode trick years ago on my '89 K5, but it was finicky, probably my lack of care, money and time as a college student was more of a factor, though.....

 

[yevgenievich]

The relay is fine. Diode was just a simple to add option

 

[charlesg]

I did this conversion yesterday, way cool! Thanks for all the help all yall.