1978 headlight problem

[Bill H.]

After a short period of time headlights flash on and off intermittently. Replaced headlight switch - still happening. any suggestions? I checked black ground wire from headlight wire loom - good ground. where are the other grounds? I am thinking bad ground somewhere.

[Terry M.]

Re: 1978 headlight problem

I believe (to be confirmed by others more versed in 1978 than I am) that you have a circuit breaker that feeds power to the headlights. Two things can cause it to "trip." More current draw than the breaker was designed for (perhaps halogen headlamps were installed), or the breaker is failing and tripping at a lower current level than it was designed for. These breakers are designed to reset themselves when they cool down, so the "flashing lights" is the normal failure mode.

I would be guessing if I told you where the breaker is at, but your Owner's Manual should tell you. My guess would be that it is in the fuse panel, but WTFDIK? I am also guessing that your Corvette has a circuit breaker for the headlights, but at some point Chevrolet went to this system on all their vehicles, and 1978 sounds to me like it was time for Chevrolet to "modernize" the electrical system.

[Tom R.]

Re: 1978 headlight problem

I believe (to be confirmed by others more versed in 1978 than I am) that you have a circuit breaker that feeds power to the headlights.

I would be guessing if I told you where the breaker is at, but your Owner's Manual should tell you. My guess would be that it is in the fuse panel, but WTFDIK?

Terry...you did well. Circuit breaker (a self-resetting circuit breaker) is in the light switch and trips when it overheats from overload...such as your example halogen lights.

According to the electrical schematic, the suggestion is to replace both light switch and dimmer switch if lights do not come on.

[Tom R.]

Re: 1978 headlight problem

After a short period of time headlights flash on and off intermittently. Replaced headlight switch - still happening. any suggestions? I checked black ground wire from headlight wire loom - good ground. where are the other grounds? I am thinking bad ground somewhere.

Three circuits are interconnected, headlight switch, dimmer switch and the speedo/tach cluster printed circuit card.

So try the dimmer switch. Do headlights stay on for either setting (dim vs bright)? If neither come on...replace both. You can just leave them dangling in the circuit without assembly for the test. The power from the light switch routes through the dimmer.

Also, if the HIGH BEAM INDICATOR light does not come on when the HEAD LIGHTS are bright, check the speedo/tach cluster ground by observing proper lighting of the TURN SIGNAL lights or the BRAKE LIGHT.

There was published a 1978 Electrical Troubleshooting Manual that is pretty handy that also illustrates locations of components. The link is the headlight circuit...you'll have to flip but should help with diagnosis.

http://www.hunt4cleanair.net/Articles/lightcircuit.pdf