Headlight Problems

[1972GMCsierra4x4]

So my headlights have been slowly going out one by one. I started out not having any lights on my dim circuit with all four lights coming on when I switched to brights. Then a few days later, only the punter two lights worked and as of yesterday I have only one headlight, my drivers side outer. My mechanic said I need four new bulbs, but installed all four of the ones I have now about a year or year and a half ago. What could be causing this out of the blue. I have replaced my dimmer switch and that didn't help. Any ideas?





72 GMC Sierra K-2500, 350 with 600 cfm edelbrock and edelbrock performer intake. D44 front and D60 rear

[Don Quixote]

The harnesses that plug into the headlight go bad over time and if the ones on the driver's side go bad, the whole thing gets screwed since they are wired in series. Replace the connectors that plug into the headlights. You don't even need the actual harnesses as long as you use the plastic wrapped blade connectors.

I have had all these problems and I spent years jerry-rigging the harnesses until one day I got fed up and replaced the blade connectors altogether. I've never had a problem since.

[swamp rat]

Check all the connections to be sure they are clean, check the grounds to be sure they are clean. , unhook one light and see if you have good voltage to the connector, then plug it into the light and check the voltage at the opposite connector. If you have bad voltage at the first connector trace it back to the light switch it may be going bad, all the voltage going to the lights in a stock system passes thru the light switch.

You may want to consider installing a light relay system, they feed direct battery voltage to the lights and use the voltage from the light switch to activate the relays, the lights are brighter than a stock system

[VetteVet]

Get yourself a piece of 12 gauge wire about 5 feet long and connect it to the positive battery terminal. Then pull the left outer headlight plug off and touch the wire end to the tan wire in the plug. Your right outer headlight should come on. Then touch the light green wire and the two bright lights and the left outer light should come on. If the light grounds are good and the bulbs are good then your problem is low voltage from the headlight switch. The blue wire to the dimmer swiitch is the power wire so you can also jump between it and the tan or green wire in the connector and your lights should all come on. The outers with the tan wire and all four with the green wire.

[Wrenchbender Ret]

Check the charging voltage. If it is too high it can burn out bulbs or shorten their life. It should be 14 to 14.5 volts.