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I've reworked my headlights a few years ago by upgrading the wiring and installing composite headlamp assy's. They've worked all this time until recently. For some reason, the low beams would be on without the switch being on. I recently had the truck inspected in Texas but i needed to replace the low beam relay to get them to work. Now that i got the truck here in Ga, i drove it to the store and it rained like mad. After being back for about an hour, the lady next door came over to tell me that my lights were on. The running lights were off and when i checked the switch, it was off. I cycled the lights a few times and they went off. I periodicly checked them throughout the evening without any problems. I was showing the truck to a fellow gearhead from work and i noticed that the low beams wouldn't work. I cooked another relay!
Im using the Bosch type, 5 pin relay for my lights. Does anyone know if pins 87 and 87a tie together? Or does power go to one or the other depending if the relay has power to it or not?

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

pin 87a recieves power when the relay is not energized... pin 87 recieves power when the relay is energized... If they are tied together that would explain why your lights stay on....

and just to finish off....

pin 30 is is your main power supply... and pin 85 and 86 are to energize the relay (switched power to one, and ground to another.... or switched ground and constant power depending on what activates the relay)


Hope it helps...
~Aaron

This has me confused... I've been using 87 and 87a as the leads to each light assy. The high beams are the same and they still work correctly. I'm going to change the wiring and see if they hold up.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

I piggy-backed both headlight leads to pin 87 and the lights functioned correctly. I pressed on with other items of the truck and went for a test drive without the hood. It felt great to drive it around! I found myself following behind a work truck and iI heard him get on it. I put my foot to the floor and i found myself having to let off so i wouldn't run up in to him. I was all over his ass! I got back to the house to install the hood so i could drive thru town without bringing any attention to the local law. The little old lady next door noticed that one of my headlights was on. This headlight problem is a Bitch! Somehow im getting power to the passenger side low beam (4 headlights) The relay isn't fried because it will still function correctly. I'm starting to think that my light switch is going bad. I think is feeding power to my lights.
But i wonder if mounting the relay sideways could be the cause. Maybe the coil in the relay isn't releasing fully. Any thoughts?

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

If the inside of the relay is rusty, this could quite possibly be the case.... I've had relays stay stuck on because the weather got to them...

Im not sure....

As far as the headlight switch goes.... Just wire up a temp. switch and try that out for a while... that should tell you if that is the problem....



Good Luck,
~Aaron

In my haste to install new connectors on the relay wires, i made the mistake of crossing 2 of the wires at the relay. So as of now, the relay is new, it's wired correctly with a piggy-back for both headlight leads at pin 87. I'll give it a shot and see if it holds up.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Some relays are not rated for 100% duty cycle. That could be a contributing factor to the problem.

The other thought is if you do have problems again, unplug the connector to the light switch under the dash. If it kills the lights you know where your problem is.

Well...They failed again. I took the headlights apart and checked the connectors and wiring where they feed thru the support structure. I didn't see any chaffed wiring but i opened up the feed thru holes just to play it safe. I did a continuity, voltage check of the wiring and it's all good. I reassembled everything and it works again. I took the old relay in to the house and took it apart to see what actually failed. The relay had water in it!!! Apparently, the way i mounted it to the firewall is the problem. I routed the wiring and the hi beam relay sits straight up with the wiring at the bottom and the low beam sat sideways. During a good rainstorm, water would along the hood seal and drip on to the relay. water would seep in to the relay and cause the problem. This explains why the lights came on with the headlight switch off. I sealed the relay with RTV and located it so it would sit upright on the fire wall. I'm confident that the problem is solved. It was killing me trying to figure out why the 4 light hi beam relay was working while the 2 light low beam was failing.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.