Help Please! High beams blowing fuses.

[bikewhorder]

I blow a fuse if I try to turn on my high beams. It knocks out the headlights and tail lights when it happens. This problem has plagued my car for years now and I'm going though it to try to get it ready for an event and I would love to figure out why this happens. So far all I have done is clean up all the major grounds because a couple people I asked about it said it is probably a bad ground. It did not help the issue. I have the large color coded wiring diagram but I'm pretty inept at solving wiring issues and would be open to any suggestions as to how to trace out this problem. Please help if you can. Thanks -Chris

[Byron510]

Chris, by chance you don't have metal backed lights do you?

The Cibie designs and older H1 lights were this way. If this is the case, you need to wire them into a separate reply, tripped by your stock system that allows ground to chassis.

Maybe this will help.

Byron

[510rob]

http://www.the510realm.com/viewtopic.php?f=32&t=29172

[okayfine]

As Byron indicated, you have some sort of short in your high-beam circuit. You need to inspect the wiring and components to see if there are any obvious signs of wiring damage. If you blow fuses immediately upon flicking the highbeam stalk, the issue should be relatively easy to track down.

[bikewhorder]

Chris, by chance you don't have metal backed lights do you?


Byron

I'm not sure but I can't even remember if I've ever replaced the lights in this car (I've owned it for 16 years) and I know this was not a problem until few years ago. I'm going to go out an investigate some more and I'll let you guys know if I find anything. My diagram shows how to rewire the headlights with relays to bring it up to a more modern standard but I really wanted to find the problem before I go altering it. Thanks for the info so far. -Chris

[RMS]

sometimes the point tower in the early relays can become lose from over load, swivel from the weight of the wire then short. rally cars are more prone to this.
I will assume your car is a 68 or 9 as you state : It knocks out the headlights and tail lights. latter cars had separate fuses for left and right headlamps. a 68 canadian shares the same fuse for all lighting off acc. I am not familiar with the 69 usdm 510 but if its wired like my 68, I would disconnect the relay on the back side of the passenger side strut tower and rule out anything on or under the dash.

do any fuses pop with the light sw pulled out one notch when the high low stock is cycled ?

I have a colour "place mat" diagram for the 68 and its wrong in a number of spots....dang..... I have a stack of books and not one correct diagram for the 68......

[okayfine]

'69s have the more modern electrical system of the later cars. '69 fuse boxes have L and R headlight fuses. '68 was the oddball with the mini fuse block.

[bikewhorder]

Well my car is titled as a '70. This is what the fuse box looks like. I replace the headlight relay a few years ago with the new one that Nissan sells but it made no difference.

[okayfine]

That's not a '69 box, probably a '70 box (depends on how many free wires). '69 boxes have pigtail connectors. If it all worked before, then the fuse box isn't it (as long as it's clean). DQ has an article on fuse boxes if you want to verify what year you have.

[RMS]

is that a velocity stack welded to the cowl ?

with it being a 69+ harness it would have multiple fuses controlling the lighting. how many fuses are blowing ?

on my 69 with a 70s harness 3 fuses control the lighting: markers/ flashers, left head light, right head light.

[Chickenman]

When I worked for New West Datsun, we had an Irish mechanic who was a wizard at finding electrical shorts.

He was particularly good on warranty work. Note: Warranty work is those days didn't pay for diagnostic work. Only for replacing faulty parts or physically repairing a wiring harness. It could take a mechanic couple of hours to trace down a short in a wiring loom or a defective relay, but warranty would only pay for the time to replace the damaged part. That could be as little as 10 to 15 minutes by the Warranty book.

This guy could always find the problem in about ten minutes. And he always had defective parts to return. His secret? He kept a stash of 50 amp AGC fuses in his Tool Box. He'd replace the fuse that kept blowing with the 50 amp one, then sit back and have a Cigarette ( yes it was the 70's ) until the smoke started to come out of the wiring loom and/or component!!! He'd find the problem in a jiffy, order the new part under warranty and everyone was happy. If he was really lucky the whole wiring loom would catch fire and that was about a 10 hour job. Which of course was paid for by warranty, because he had a melted wiring loom to turn in... Brilliant!!

[datzenmike]

Unplug all 4 lamps and see if the fuse blows in the high beam position.

Yes... not the lamps, you have a wire grounded
No... high beams are after market halogen and drawing more power than the wiring and fuses are rated for.

[510rob]

good point Mike!

[bikewhorder]

Thanks guys I'll try the unplugging trick first! And no its not a velocity stack, just a vent tube of some sort that I'd never thought was unusual but I have no idea what its function is.

[bikewhorder]

Ok, so there's a big clue, All 4 headlights disconnected, turn on the high beams and the solder bubbled out of a 20 amp fuse.