1970 Lighting Issues

I recently upgraded my exterior lighting to LEDs for everything but headlights. Bought the kit from WC which included the flasher relays and new sequencer. Everything installed and working until last night.

While driving noticed left and right turn signals stopped working.

Got home and started playing with things.

Brake Lights - only Driver side

Taillights - both sides working

Headlights - none

Turn signal - neither side working, no dash indicator lights

Emergency Flasher - only driver side, seq working, both dash indicator lights are working.

Today got to the fuse panel and thought I found 2 blown fuses. Replaced all to be safe, but no changes in behavior.

I am stumped and looking for any ideas. This is a bit out of my wheelhouse but don’t mind working through it. Any help will be greatly appreciated.

It sounds kind of like the turn signal switch had gone south. Use this trouble shooting guide to help you out.

It could be bad grounds too.

The headlights should be totally independent of the turn signals and brake lights. The turn signal and brake light issues sound like the turn signal switch as the most likely item.

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Thank you for the input. Based on some tracing and poking around I think I have 2 issues at the moment.

Turn signal switch
Circuit breaker

Based on testing I 75% believe my grounding is good.

Any tips on getting to the circuit breaker will be appreciated!

Circut breaker built into headlight switch . Will sometimes just flash if a minor overload( high draw halogen bulbs can do this)

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You should take a closer look at the passenger side wiring. Also, checking the function of the front parking lights and side markers may better define where the issue is.

A mystery solved; thanks! I picked up a '70 Cougar in Montana and began the trip to Florida by heading South first to Ft Mohave AZ. First day of driving at nightfall, turned on the headlights and they would stay on for a few seconds, then go off for a few; kept cycling on and off. I opted to not drive at night for the rest of the trip. Once I started working through things I found the halogen headlamp incompatibility and have ordered 4000/4001’s. At least now I know WHY they were doing what they were doing!

Retro1, I had that happen with my 71 XR-7. It had 4000/4001 lights in it. Some times the circuit breaker in the head light switch goes bad. In my case a new switch fixed the problem. This is just a FYI incase the new bulbs don’t fix the problem.
Driving from Montana to Florida sounds like a great adventure. Please make regular posts of this trip.

You could use the halogen bulbs by using rocketmans relay kit

I was able, after the first incident, to drive with the lights on for short periods without a repeat; but I really don’t want to lunch my harness. If it happens again after I get the OEM bulbs in I’ll look into the circuit breaker - presuming I can find it.
The trip was an enthralling exploit, particularly with the errant steering. We went through pieces of 12 states (excluding Florida). At first I was keeping it between 2500 and 2800 rpm while getting comfortable with the car, but with speed limits at 80mph, and everyone doing 90 I eventually fell into the 3000 to 3500rpm groove. Thankfully, it is all history now!

Thanks for that; I had heard there was a relay available, but I’ve also heard that it may compromise some of the other instrumentation lighting. Since I really don’t expect to drive at night, sealed beams will likely be fine.

FYI, The circuit breaker is built in to the headlight switch.

To replace it do you have to replace the switch?

Yes you do.


If you want to stay with the halogen lights, here’s a plug-in kit that supplies relays and a circuit breaker for the higher amp draw.

It worked well for me.

70XR7Tom - Appreciate the link and testimony; thanks!