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Guys and Gals

1) install 2 new headlights
2) few days later passenger side low beam burns out. hi works. driver side all works
3) install 2 new headlights again
4) both sides work low beam upon install
5) 5 min later passenger low beam passenger side burns out. hi beam works. driver side works fine.

comments please.

Ken

Are the filaments actually burning out or just not lighting? The light circuit is very simple on those years compared to earlier so I'd first wonder about the condition of grounds, connections and wires. Of course, if the bulbs are actually burning out I'd really wonder about the voltage present or quality of the bulbs.

Essentially, turning on the headlight switch feeds a single wire with 6v directly to the dimmer switch. The dimmer switch selects one of two terminals and feeds the voltage on out to the terminal strip on L side of fender. It picks up one headlight bulb directly and from the terminal strip also supplies the crossover cable to the terminal strip on R fender for that bulb. Since the bulb filaments are in parallel, if one lights and one doesn't it would seem to be a ground or the wiring connecting the two lamps.

I think the first thing to do would be to check that you have 6.3 volts sitting and no more than 7.4 volts when the generator is charging. If good, just as good housekeeping measure I would suggest you remove the connections from the dimmer switch and terminal strips and clean the terminals. Oxidation is a big problem on some of the metal terminals. If all that checks out then lastly the condition of the bulb sockets and finally, the bubs themselves.

You can also check the crossover cable between the two terminal strips and make sure it's in good condition. IIRC, it crosses over in front of the radiator on those cars and is held by a couple of clips. The old rubber can fall off in chunks if disturbed but not likely an issue unless the breaker is tripping.

The dimmer switches are a known source of trouble but a problem there would not result in one side lighting and one not. Typically a dimmer switch failure would be both sides not lighting a particular filament or else a direct short and the circuit breaker tripping.

Did a previous owner "improve" the car by installing an 8V battery? Look at the battery, count the number of caps and multiply by 2.

Check where the bulb plugs into the plastic harness. I had the same problem with my driver's side light. The terminals on the ends of those wires were loose on the prongs of the headlight, causing the low beams to not work at certain points or at all. I popped the wires out of the plastic harness and pinched the connections with pliers so they would be tighter on the headlamp prongs. Success! Just something else to look out for if you're still having problems.


-Garrett

Does the burned out bulb work if pluoed into the driver's side socket?

Overcharging Generator? But I would imaging other lights would be affected as well.

Make sure all the grounds are clean. Dirty ground, higher resistance....

update:

finally got some time, voltmeter shows 6 or so volts at same time (hi and lo) on fender wall block. so it appears that both hi and lo were on when hi beam engaged. removed hi beam wires from block on fender wall cleaned reinstalled. then meter again and voltage as it should one at a time. hope problem solved


Ken