Classic/Antique Car Repair: Cadillac Headlight Problem, Headlights wont work after storage

Question
HI:  I have a 1967 Cadillac Calais coupe.  It has been sitting for a few years, and the headlights no longer work on either high or low beams.  I replaced the light switch, but that did not fix the problem.  Since the headlights and the parking lights are on the same circuit, and the parking lights work fine, I am at a loss.  Could it be the dimmer switch on the floor?  I have tried stepping on it repeatedly, to perhaps see if it does anything, but no luck.  Do you have any suggestions?

Answer
I am hoping that your car does not have either of the automatic headlight options (either the "Twilight sentinel" or the Automatic Dimmer).  If it has either of those, they are the first suspects, and the first step is to turn off, disconnect or bypass them to make sure they are not causing the problem.

If it is just the plain normal headlight system, I would have told you to try exercising the dimmer switch, and you've already done that.  Do it about 50 more times with the headlights turned on, often this will rub the oxide off the internal contacts and get it working again.  

The next thing to check is the circuit breaker on the headlight switch.  This powers the headlights separately from the parking lights, so the fact that they are working doesn't tell us anything about the headlights not working.

Check the two wires on the circuit breaker - it is on the back of the headlight switch and can be identified by the thick wire going to it. It looks like a tiny bathtub, about 3/4" by 3/4" by about 1 1/2 inch long, with two terminals on it. It should have 12 volts on both terminals when the headlight switch is turned on.  If it does, then the problem is in the dimmer switch either because the wires to it are not making contact, or because the switch has failed.  This often happens when a car is left to sit for a long time, and that is why exercising it often restores the headlights - so try that some more before you start tearing things apart.  You can check the wires to the dimmer switch - there should be 12 volts on one terminal all the time, and the other 2 terminals should alternate having 12 volts each time you operate the switch.

If you trace it to the circuit breaker, take it off the switch and use it as a sample to show the parts guy at your NAPA parts counter - replace it with a 40 amp circuit breaker, even though the old one was probably smaller - because modern bulbs draw more current.



Dick