Blinking Headlights

it's a circuit breaker cycling. If you have an ammeter put it inline with the wire between the headlights and the dimmer switch and let us know what you find. It's probably a 15 or 20 amp breaker so if current is less than that everything is normal and you need to replace the breaker. If higher you need to figure out where the short to ground is and fix it.

Can you hear the breaker cycling when the lights go on and off? if so, and you don't have an ammeter, you might also want to try unplugging the headlights, if the problem persists (i.e. you can hear the breaker cycling) even with the headlights unplugged, there's definitely a short that you need to find.

good luck

nate

Had this happen also. different vehicle. Found a wire going to tail light had worn through the insulation and shorted to frame (ground). This keep tripping the circut breaker. WW

I used to see that lots on the old beasts. It happens with halogen bulbs. If you can't find the old style regular GE light bulbs or just want to run the upgrade to halogen, you need to add a relay to the circuit or you will blow that breaker. They used to include wiring kits with halogens back in those days.

You just add a stock bosch relay with direct fused battery power and the headlight switch with the breaker turns into a low amp trigger wire.

If you already have the old standard bulbs, then you likely have a rusty contact that is arcing creating heat. Suspect the harness plug for the headlight switch as having a rotted plug in it. These can be replaced pretty easy and the socket can even be replaced as a 'Help' brand product that I have seen on the auto parts store shelves.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: N>

There's a thermal circuit breaker in there SOMEWHERE that is cycling. It might be a real overload, but not likely since you say it takes 2-3 minutes to start. Its most likely just the fact that thermal circuit breakers get trip-happy when they get old and will start cutting out WAY below their rated current. On most Mopars the breaker is built into the headlamp switch, but you said you already replaced it. It could be that the Trailduster has a separate thermal breaker, or it could be that you have a real problem, or it could be that the breaker in the new switch is weak also. Trace out the feed wiring to the switch and if you find the thermal breaker, replace it. If you don't find it and can't find a short, its a good idea to put the headlamps on relays to take the heavy load off the old switches and wiring anyway. That will prevent the breaker from nuisance-tripping. Install new fuses or breakers on the relay wiring to protect the circuit. Daniel Stern has good relay installation diagrams on his website:

Hi, Porky, I've seen older cars that used fuses almost exclusively develop an intermittent short that would keep blowing fuses. When the troubleshooter could not readily find the inter. short, he'd replace that fuse with a circuit breaker from the likes of AutoZone. Then, when it came time for the fuse to blow, the c/b would open until the heat cooled down enough for the c/b to re-close. Saves having to carry fuses to replace at in-opportune times. If you have such a car with such modifications, it's time to locate that c/b, find the now much-more frequently-occurring short, repair it, & go back using the proper fuse for protection. HTH & good luck, s (You've probably guessed it by now: yes, I did that to my dad's 1976 Luv pickup that was blowing a fuse about once every 6 weeks

Your '79 was originally equipped with low-wattage headlamps; some of the first halogens, 35/35w low beam. Most of the present-production H4656 sealed beam high/low units are 60/50w or thereabouts. Situation is similar with the H4651 high beam units. When the wiring was new, it was (barely) able to handle up to 65/55 high/low plus 60w high. Chrysler has never put very good headlamp wiring on their vehicles. They didn't in '79, they didn't in '69, and they don't now. The blinking is caused by the thermal self-resetting circuit breaker (located inside your headlamp switch) heating up and cutting out.

Fix it this way:

Hey, Dan, one heck of a nice site. Thanks for your help. s

Thanks for the "thanks"!