I was thankful to finally arrive at a very brightly lit intersection.
Headlight Problem
Over the summer I have been driving the 1955 Ford Fairlane several times a week and multiple times a day. The excursions have included various times of daylight and evening hours. For the most part, things have been just fine; however, one night a few weeks ago I experienced an electrical problem that I have never encountered. After ten minutes of driving at night on these dark roads in the desert, the Ford's headlights mysteriously went dark. The dash lights were fine, the tail lights were bright, and all of the other lights, including the parking lights, were operational.
I jiggled the knob and pushed it in and pulled it back out. That did not seem to do much. The headlights would both come on and go off at random intervals, sometimes staying lit for 2 or 3 seconds and at other times only for a brief flash. Thankfully, I do have good fog lights, and my tail lights and my brake lights were all working just fine. Within a few minutes I pulled up to a brightly lit intersection not too far from home and was glad when I finally pulled the car into the garage!
The headlights were flickering on and off intermittently after glowing steady for 10 minutes.
Solution
To me, this problem was a head scratcher. Since the installation of the Rebelwire wiring harness several years ago I have had no trouble. The harness was not that difficult to install, all of my leads and terminals were good, and over the past few years the circuits I have added have worked flawlessly.
"Has to be a ground somewhere that is corroded..." I muttered to myself.
I attached a 12 volt charger to the battery and set the charger's switch for 2 amps. This was to be sure that I did not run the battery down during my tests of the headlights and all the time I thought it would take to troubleshoot. I removed the headlight hoods and checked on the ground wire for each headlight. After turning on the headlights and waiting roughly 10 minutes for them to start flickering, I ran a direct ground wire from each headlight to the battery post itself.
That was not the problem.
I doublechecked the fuses under the dash; no problem there either. Consulting the fuse panel diagram from Rebelwire I expected to see a headlight relay. The only relay I saw was the horn relay. Then it dawned on me. I had never installed relays for the headlights! For whatever reason back when I ran all of the wiring to the lights I did not set up relays. Over the past several years I have run relays for fog lamps, carburetor choke, and even my own custom relay harness for the overdrive solenoid. The back up electric fuel pump runs on a relay circuit as well. Looking back, I guess that since the new headlight switch I had installed operated the headlights just fine I assumed there was no problem.
My attention turned towards that reproduction headlight switch. Believing that the internal circuit breaker in the switch was being overloaded (cooling and resetting itself causing the flickering of the lights) I dug out a couple of Bosch-style relays from my electric tool cart and started prepping terminals.
I installed two relays right beside the horn relay since I had a power stud on the air deflector.
If you have never wired up a relay, let me tell you they are a wonderful thing. Essentially, a relay allows the full power of the battery to be wired to your accessory (or in this case, a headlight) without the full amperage draw running through the switch. Therefore, the switch acts as a trigger for the relay ensuring that the very minimal amperage flows through the switch, protecting its life and internals.
Headlight wiring diagrams are extremely helpful. (image creator unknown)
The diagram above is close to what I ended up using in the 1955 Ford. I did use 12 gauge wire and a 30 amp fuse to power the relays. Thankfully the Rebelwire harness is easy to trace with wiring leads that are stamped with their intended use (horn, oil pressure, headlight low beam, headlight high beam, etc). Splicing into the two leads for the headlight low and high beams was actually quite easy to do. As the photo above shows, I connected all the terminals and tested the new relays before taping everything up.
Installation of the relays made the lights burn steady with no issues!
This brief post ends with a video that shows the trouble I was having with the flickering headlights, the way I tackled the problem, and the end results. Needless to say, I am very happy with how it solved the problem and now, I am ready to drive again at night!
The Hot Rod Reverend
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