Relay to supply alternative power to load

Apparently, as wiring harnesses age they develop inherent resistance which can result in less voltage at the end of a run. One of the ways to address aging wiring harnesses with regard to lighting in older vehicles is to feed the headlights off of a relay triggered by the factory harness to bring back some of the lost light.

My problem is that in the event of a relay failure the lights go out. Not so good. So I figured that if I could power the headlights with the factory wiring and subsidize the power to the headlights with a relay I would have the best of both worlds.

However, by adding a jumper between 86 and 87 (30 Pos, 85 Grnd), I end up with half a latching relay, turns on, not off.

Any ideas of how to add redundancy to this circuit and keep it fairly simple in the process? Maybe add a diode, if I could find one large enough?

Curious....

I would just put in a relay... and besides... it would be easier to replace then to re-wire..
Relays coils are around 80 to 90 Ohm... so not much current is needed to pull them in...
So.. this aging wire should have enough current capability to drive this small relay... IMO

lml

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xyzzy

I was thinking of this, but hoping for a simpler system than 4 relays (for redundancy). I guess I could do two relays (one for hi and one for low). Still hoping to have the original power lead supply backup power. I know this works. I think I will check and see how much difference a relay will make.

I wouldn't bee too concerned with reliability of the relays. If one fails, use the other beam until you can fix it. I have a 2 relay system in my DD pick up with 90/130 W H4 bulbs. The install is now 14 years old with not a glitch ever. I drive it every day, and night too. 14 years at 14 amps and the relays are the original installation. Seems reliable to me.