Headlight Problem with my 74

Both headlights quit simultaneously. Bulbs both check out. Parking lights, tail lights, turn signals all work. All of the painted labels on my fuse block are worn off. Does anyone know whether the headlights were fused separately from the other exterior lights on a 74? I couldn't see any blown fuses with a flashlight and my bad eyes. Any ideas appreciated.

 

check fuses with ohm meter, but before that make sure the connection is good at switch and ground is still intact

 

The power to the light switch comes from a battery hot wire from the alternator to a fusible link then runs on to the head light switch. The dash/park etc is powered from a separate source from the fuse block. So you will not have a fuse for the headlights but will have a fusible link wire.

 

The headlamp switch is a GM type with built in circuit breaker.
Typically, you'll see overheating issues with the plug and/or wiring where they connect on the switch.
It could also be a switch/wiring problem with the floor mounted dimmer switch.

 

had dimmer switch failure across many vehicles that would be my first spot to look

 

JMO - forget trying to figure it out in advance. Get your meter and start tracing the circuit back from the headlights to the battery. You have to be systematic with electrical. Find where the power stops, and that's your failed component.

You might get lucky and go right to the failed part, but it could be something unusual like a bad connector or chafed wire. You will only find problems like this by being systematic and measuring the circuit. Measure, measure, measure.

There is a wiring diagram in the '74 TSM at http://oljeep.com/gw/74_tsm/22-7-CJWiringDiagram.pdf

 

A '74 does not have a fuse block from the factory. Inline fuses only. 1975 is the first year for a fuse panel in a CJ-5.

 

In general, headlights were not fused. A relay, often on the back of the switch, will interupt them momentarily.

I always assumed this was a safety feature - so as not to leave a driver blind while at speed.

If the relay is good, I'd look for a break in the wiring or a bad dimmer.

 

If you find that you may have to repair some wiring anyway, this may be a good opportunity to re-wire the headlights through a relay. This will allow the headlights to see full voltage and eliminate the need for the headlight switch to support the electrical load, as it will merely serve as a trigger for the relay. There are kits out there from IPF, or Howard Stern Lighting. Not necessarily cheap, but a good option. I've got this setup on my TJ, and have the parts for both of my CJ's. Big difference.....

 

This can be done for way less using relays and plugs from the flaps. It is also possible to wire them so the high and low beams are both lit on high using three relays.

 

I'd be wary of this possibly over overheating the sealed beams and their pigtail connections. Has anyone experienced such results?

 

Not yet have been running the boys like that for a few months now. Have seen kits that did the same on a newer truck and they have plastic lamps and hot bulbs.

 

I am genuinely curious. I tried it many years ago, but a burned-out sealed beam made me back off. Possibly coincidental.

On my Harley I have upped the wattage in the H4, and the pigtail partially melted. I believe "hi-temp" connectors are available for such reasons.

 

Yes, you can buy ceramic headlight sockets for such a purpose.

I think the cheapest source of relays and sockets is Parts Express - "12 VDC Waterproof 5-Pin Bosch Style Relay SPDT 30/40A with Metal Bracket" from www.parts-express.com!

Lots of articles on the 'net about how to do this.

IMO, rather than running the low and high beams simultaneously, I'd suggest you buy some halogen lamps and run them the usual way. The Autopal lights on eBay get generally good reviews. 7" H6024 6014 H4 EURO CONVERSION HEADLIGHTS KIT Euro style is not DOT approved, but the light pattern on low beam is superior.

 

I had problem with the oem swith before, getting too hot or something like that, so ended up using a remote toggle swith for headlight.

The footswitch could be the problem too , i would check it

 

25 years ago my fuseable link melted down in wire harness then repaired. Latley i found the connection of headlights wires and ammeter wires all connected while looking for backfeed into the headlight switch.. I put a master switch continious duty solenoid in so i could control the interior electric feed. The ammeter will be tossed. I connected the wires backagain finding corrosion in the factory splice. I respliced. ,now i can turn off all power with a master switch which is safer. Reason tellin you is a factory splice can be faulty.

 

I recently went through headlight issues getting my 74 lights working . The headlight switch plug was partially melted and the dimmer switch was toast. The dimmer is an easy test. Power comes in, and exits either one of two outbound wires depending on switch position. I had no power on either outbound wires. I replaced the dimmer and headlight switches, Headlights work awesome now.

 

It seems the factory splice had something to do with the headlight switch overheating on my 74 too. Last night was studying the wire diagram wire 12a and the wire to output terminal of altenator all splice at the factory splice. Somehow it was causing the headlight switch to get hot (excessive resistance) and the dimmer bakelite ceramic was super hot. Maybe this explains why it was going thru light switches.

 

A four year old thread, and the OP hasn't been seen on the site since August 2019. I'd guess he solved his problem!

 

I had the same issues with my 73. I had to replace the floor dimmer and the headlight switch/breaker. I also run the halogen lamps they are a direct swap for the old yellowing sealed beams. Don't need to run both filaments.