Our 1976 Cutlass Salon sometimes loses its low-beam headlamps, though the high-beams continue to work. When this happens, the blue high-beam indicator in the cluster remains lit . . . even in the "low-bean" position, though the low-beams have stopped working.

This car has the column-mounted dimmer switch as I believe all '76Salons did. I replaced the original switch with an original GM unit five years ago, so I don't really think that the problem is the switch itself. I replaced it because the under-engineered hi-lo-beam connector at the bottom of the column had overheated and melted-down. I replaced it with beefier Packard 56-type connectors so I doubt it is the same problem; I can smell nothing burning.

Jeff

 

First, I assume you are aware that the low beam bulbs have TWO independent filaments, one that is powered on the low beam setting and a separate one that is powered on the high beam setting, right?

Just so we're all clear, are you saying that the low beam bulbs are sometimes illuminated when on the high beam setting, or do they always go out? Troubleshooting will be different depending on which is happening.

There is just one wire from the dimmer switch to the low beam filaments, and one wire to the high beam filaments. If ANY bulbs are illuminated on the low and high beam settings, the switch and the wire up to the core support is fine. If the low beam bulbs are off every time the high beams are on, the problem is likely to be burned out high beam filaments in both low beam bulbs. If the problem is intermittent, the cause is likely the factory splices in the harness. The high beam wire from the dimmer switch runs to the connector on the LH low beam bulb. At that connector there are three wires spliced into the terminal, the wire from the dimmer, the wire that runs to the LH high beam bulb, and the wire that runs across the core support to the RH low beam bulb. If that crimp is loose or corroded, you can get intermittent problems like this.

 

Joe,

The low-beam headlights will often go out ENTIRELY when I switch from high-beam to low; when this happens, the little blue high-beam indicator in the instrument cluster STAYS ON, even though no headlights are burning. When high-beams are on, the low-beams will always come on with them. I hope this clarifies the situation.

Jeff

 

Thanks for the clarification. In that case, it sounds like a switch or intermittent dash wiring problem. The high beam telltale in the dash is powered directly from the dimmer switch. If it stays on in the low beam position, there's a switch or wiring problem. When this happens (telltale stays on) are all the lights off?

 

Yes. It happens when I switch form high-beam to low-beam; all of the headlights go out, but the blue indicator stays lit.

Jeff