Headlights Relays In Absurd Detail

Addendum about Fusible Links

Earlier I wondered whether the fusible link might be a better option to the circuit breaker I used for this project. I've thought about this a little more, and decided that would be a bad idea.

When you splice in to the existing wiring to power the relays, you connect the headlight wiring from the fender to the lights to the relays. These are the 14 ga gray with trace and 16 ga gray wires going across the fenders. One cannot protect a 14 ga or 16 ga wire with the 14 ga fusible link that would protect the big red 10 ga wire.

When one has a circuit with mixed wire sizes like this, one must protect all the wires, not just the largest wire. Now, 10 amps at 13 v through that 14 or 16 ga wire is fine, and protecting that wire with a 30A or 50A circuit breaker or fuse would work fine. The fusible link would not protect that smaller wire. Not a good idea.

 

I did edit the point where the topic is first discussed with something like that.

 

Dang. I guess I'll have to go back to my invoices and check to see what headlight upgrade I did. I definantly was not aware of the additional wiring and relays needed to run a safe upgrade. So my rig being a '74 might have the light switch w/ fuse? I just remembered I bouaght a replacement but hav'nt swaped it out yet. Will I need to make additional changes similar to this when I add driving/fog/spot lights and a winch? This is first rate Tim. Thanks again for sharing. Superb detail as well. CC

 

Thanks for the kind words.

The lights sold as "direct replacement" should work fine with your existing wiring, at least for a good while. No question the relays will make the switches last longer, though that may be say 100 years instead of 10 years. Certainly the more-direct wiring will make your lights very noticeably brighter.

A '74 does indeed have the "old" style wiring harness, with inline fuses and (I'm told) a circuit breaker in the light switch. There are post earlier in the thread that discuss this. Jeep switched to the bulkhead connector and fuse panel design (and a voltmeter) for 1975. Of course, 1976 changes again, with the addition of the GM steering column.