I have experienced a very strange failure on my 1966 E-Type OTS. For over 2 years, I have had the headlight low-beam filaments fail while driving at night. Here is what happens: I am driving along and for just a second, both low-beam bulbs suddenly get noticeably brighter and then...darkness (no light output from either bulb). I then use the dip switch to change to the high-beam filaments and then have enough light to drive home. When I change the headlight bulbs, everything works as it should. I have replaced at least 4 sets of headlight bulbs to date. Most recently, I replaced the headlight switch on the dash. I am hopeful that someone has the solution to my car's frustrating problem.

 

Sounds like it might be due to a voltage spike from a bad regulator. Do the dash lights brighten too when that happens? I'm not generally a fan of the "spray and pray" school of fixing things but you might try a new voltage regulator.

 

Might be the regulator as mentioned but when it fails the voltage should change slowly. I would be suspicious of a loose connection at the battery. If that disconnects the voltage will spike quickly, especially if the alternator revs are high like when driving at speed. Check both terminals.

 

I have ordered a new "control box" (voltage regulator). When it arrives, it is an easy swap. I gonna cross my fingers for good luck! Thanks!

 

Thanks for the idea. I will first change the voltage regulator ("control box") when it arrives this week. I will also check the terminal connections.