while driving my 54 3100, with 235 engine in the dark. Lights went off. a few seconds they came back on. this happened until i got home. reading the manual it says there is an interupter in the head light switch that would cause this if there is a short which caused a current draw over 42 amps. I replaced the switch while working on the truck. This was the first time i have driven it at night. Does anyone have any suggestions for finding the short. i drove the truck in the daylight with my bright lights on and saw the interruption in the bright light indicator light on the dash. Alny help would be appreciated. it started after driving for a few miles with the lights on. Thanks
A light switch has a bimetal strip that acts as a self-resetting circuit breaker so you don't lose the lights entirely like would happen with a blown fuse. The dimmer switch is a good place to start looking for a problem. It lives in a very bad environment- - - -lots of road splash, salt, etc. It can develop a short that will cause the breaker to cycle. Try disconnecting the wires at the headlights one at a time to see if the problem goes away. If not, keep backing up along the wiring, from headlights, to the dimmer switch, to the headlight switch, disconnecting wires until the circuit breaker stops cycling the circuit on and off.
Did you happen to install brighter headlights recently, like halogens or LED's? Some of those types of lights draw enough current to need relays in the circuit to prevent overloading the breaker in the headlight switch. Jerry
The murder victim was drowned in a bathtub full of Rice Krispies and milk. The coroner blamed the crime on a cereal killer!
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Another suggestion is that it could be a dirty connection causing resistance at the bimetallic strip that Hotrod Lincoln references. This happened to me and there was no short, just needed to clean the points at the connection. What happens is that the dirty connection gets hot with a normal current draw, as you would have with the headlights on, and the heat causes the bimetallic strip to open the circuit. After 5 minutes, things cool down, lights come back on, only to repeat every few minutes. Kent
First thing I would do is a thorough inspection of the wiring. Follow the wires from the headlights back to the switch. Look for places where the wires could be grounded by chafing against metal. Look for areas where wires could have had the insulation burnt off by hot parts such as the exhaust. Look for wires spliced together and wrapped up in tape (possibly highlight pigtails); a good place for short circuits.
Reread Hotrod Lincoln's post about disconnecting the wires at the headlights and working back to the switch.
Does anyone know if the new headlight switches have the thermalcircuit breaker in them? The supplier who i bought it from acted like he never heard of it. I had seen it discussed in the 1954 Chevrolet Shop manual, page 12-37. my problem sounded like exactly what would happen. I'm not sure how long it takes for the breaker to cool so light would come back on. mine were only a few seconds to a minute. Scarry driving when it was a minute. Thanks for all the suggestions.
This one does (attached pic). It's from Classic Parts.
99% out of a 100% of the time, the problem is in the dimmer switch.
If you truly have a short, your are risking a fire or frying your wiring. You need to nail this problem ASAP.
1. Remove both head lamp sealed beam bulbs 2. Remove dome light bulb 3. Remove fuses (firewall box) for tail and stop lights. 4. Connect voltmeter across battery 5. Engine not running or cranking
You are looking for a significant voltage drop when you pull the knob on the headlight switch. Watch your dash ammeter gauge for a significant deflection. If your current or voltage has a significant change then you may have a problem somewhere else. Report what you see.