73 500 After about 3 minutes on bright the headlights flash on and off. Troubleshooting found the contact for the brights in the through firewall connector (nomenclature?) showed signs of overheating. I cleaned up the contact and reassembled with dielectric grease. Didn't fix the problem. When I was setting up the car I replaced all four lights with new units. Did that increase the amperage? The low beams are fine. Any ideas?
Did you use stock headlights or aftermarket hi-output versions? It could be aftermarkets have a higher current draw.
So I am not sure. but probably upgrades. They use more current, yes? I will pull one out and find out. Just two on low beams doesn't create a any problem apparently.
I'm not sure that headlights are fused. But I do know that many hi-output lights use a relay to reduce current draw.
'72-'79 light switch has a circuit breaker. Babe had this problem back about a year and a half ago, with no low or high beams after about a minute, so I cleaned the contacts in the switch pigtail and at all four bulbs. The low beams then stayed on, but the highs cut out after a couple minutes. So I replaced the switch itself, along with the dimmer switch as both showed signs of corrosion (Babe hadn't moved for a couple years and got moist inside). Now, good operation, but I will either invest in LED lighting, or I'll make a relay harness for these halogens to prevent any problems down the road.
So as part of the troubleshooting I had already replaced the dimmer and light switches. Didn't have any sign of corrosion or charring. I am about to brighten up both grounds. Will advise.
You should double check and clean all the grounds also. If the light switch is the cause you should be able to hear it "click". I had a similar problem when I hooked up a trailer. At night everything was fine until I stepped on the brakes. Then everything went dark for almost a minute. Seemed like forever at night though. I went through several light switches until I got a good one. I ended up getting one from Ford that worked best. Ones from NAPA and Autozone just didn't handle the currant draw. Lastly I would also suggest you run the power to the headlights though a relay. The wiring on these cars is not getting any younger and if you drive at night the longer the power is on the more chances you will be taking.
No doubt the bulbs pull much more current with the brights on also. Worth mentioning that the circuit inside the dimmer switch makes it suspect also. Just to add to the post above me, '68 - '71 also have a circuit breaker, mounted inside the switch body. Don't know about other years. FWIW, on a '71 with brights on it is pulling more than 2x the current that low-beams-only draw. Might be time to replace the switch or convert to driving the headlights through a relay.
Circuit breakers can age to where they will open at a lower current than specified. Also the contact points on the breaker could be dirty or corroded.
You can get headlight relay wire harness from Amazon/fleabay.130 amp alternator is a good upgrade as well.
That is probably my ultimate solution. Just finished cleaning both front grounds, removed all four lights and cleaned contacts with solvent.. Still, after a couple of minutes with fingers on the wire at the firewall connector it is heating up. This tells me the problem is from there forward. I did replace all four bulbs five years ago when I started on it: they are all listed 55/60W, made in India. Low beams work fine, only two bulbs on a different circuit. Do they make retrofit H4 LED bulbs that would be lower wattage and an upgrade together? I found a relay harness, thanks LS.
OK, answered my own question about availability of LEDs, as low as 26W draw and $18 a pair. Has anybody done this and can recommend a product? Are they too wicked bright?
I put new lenses and LED bulbs in a 94 Lincoln Town Car a few years ago. It didn't take but one drive to decide that those lights were going to get me shot at. They had excellent cutoffs and proper aim but I doubt anyone meeting my car could see the road for a few moments after passing by me. Stock bulbs went in and were plenty bright with the new lenses. I ended up modifying the headlight lenses on a JohnDeere tractor I use for mowing so the LED's would fit in them. Mowing at night is now like doing it in daylight thanks to how bright those LED bulbs are compared to regular headlights.
Final report, acquired a solenoid harness per LSC (only $15 with free shipping) and installed in 90 minutes. Works like a charm and the lights are brighter and steadier. Forum comes through again.
