In hooking up my universal wiring harness, I realized my headlamp power circuit has no fuse on it. Is designed for the GM style switch that comes with the kit, it has a 26amp internal breaker. So I'm thinking I need to add a fuse.

But looking at the mazda wiring diagram there is no fuse on the headlight circuit feed. There is a fusable link. The running lights feed has a fuse after a fusable link.

Anyone know if our headlight switch has a circuit breaker? Haynes manual or factory electrical manual are no help.

 

I am pretty sure the only fuse on the headlights is the fusible link. I haven't seen any self resetting circuit breakers on the schematics. Ok, I just double checked the 85 FSM and as you state there is a 10A fuse on all the other driving lights but only the fusible link on the headlights themselves. There is no circuit breaker. This could be different on earlier model years but it seems unlikely. So you can add a 30A fuse if you want to but if you are using the fusible link it should be adequate. Actually for safety I would fuse each bulb independently. That way a short would only drop one headlight.

 

The fusible link is the only protection for the headlights.

 

Seriously? What is that, like 20 fuses?

I think I'll just fuse it either way, cant hurt anything. Just seemed odd that the parking lights have a fuse and the headlights do not.

 

headlights have a FUSEable link.

 

Sorry, not every bulb. Just the headlamp bulbs. I should have been specific. Those are the ones you don't want to have both go out at the same time. Who cares about the others, as long as you can still see. A pair of 15A fuses should be adequate. Of course what you are really protecting against is a fire so if there is a common wiring to both headlamps you can only have one fuse.

 

Indeed you are correct, and all the headlight circuits I have worked on at work are wired this way. there is usually a main headlamp fuse and relay, and then seperate left and right fuses after. For exactly the reason you stated; headlamps are very important. Better just one goes out then both.

 

ok so i have a problem like this on my s4 na gxl '87. i had one light out but both work when the brights are on, i pulled the 15a fuse, and now, its reversed, the other one only works but when the brights are one they both work. i believe there is a short. please and thank you i don't want a ticket.

 

this all happened when my battery drained overnight when i left the key on

 

You might be better served asking this on the FC specific section. It does sound like a short though. It could even be in the bulb. You might swap the bulbs from left to right and see if the issue moves. That is reasonably easy to do and you can look at the harness and see if you can see something near the bulb. That is where the wires bend when the headlights go up and down and would be the most likely place for a break/short to occur. I did have an 87 GXL but I traded it in 89 or 90 so I never had one of these as an older car and don't know what kinds of things go wrong with them over time. I have some level of surprise that the SA's and FB's dont seem to have any overt issues with the headlight wiring harness.

Best Wishes.