Updated: Dec 27, 2019
Dome Light Wiring and Testing
There are a few more details to finish out on the 1955 Ford Fairlane, and most of them are tedious at best, being very demanding of time and talent! (both of which I have very little of these days) If you know anything about electrical wiring, then you also know that many DIY wrench-turners are easily befuddled by repairs or diagnosis when it comes to automobile electricity. One piece of the Ford puzzle I did not look forward to was the repair/restoration of the wiring on the car. Thus far things have gone reasonably well, but most of that success can be attributed to Rebelwire and their wiring harness, helpful FoMoCo wiring diagrams, and some fellow enthusiasts. Most of the original wiring of the 55 Ford had been discarded a few years back when I started this process, but even back then I knew that one day I would have to deal with the dome light and its wiring. Hindsight is always 20-20 and if I ever had this to do all over again, I would certainly wire the car as I went along with each project. Completing the car the way I did is not the recommended route. Limited space, a move in the middle of the process that necessitated the car having to move under its own power at any one given time, etc, has made challenges on this Ford I did not expect back when I began. Hopefully all of you that are reading this blog will be able take away some advice and be more efficient when you tackle a project of this magnitude.
Before I re-installed the headliner I did have the presence of mind to check the condition and continuity of the harness that led from the driver's door jamb to the dome light housing. All was well. However, the dome light switch did not work even back then. Now, it was time to tackle the issues, beginning at square one. I purchased a new bulb and installed it into the housing to perform a bench test. Nope, nothing responded.
I muttered to myself, "Good ground, good wiring, good switch... wait a sec, I'll bet this small switch is bad!"
When I first examined the switch, it looked to be something that had to be replaced... a throwaway item. Back in the mid 50's that was probably true. I checked on the pricing... most dealers had these switches at $40 each, and all the ones I located were NOS. I could not find a reproduction part. As I sat at the kitchen table and looked at the switch a little more closely, I decided to take it apart and see what made it tick.
"Who knows? Maybe I could repair it?" I said to myself.
You can see the pieces above - the whole assembly is quite simply put together. Only two screws held the switch to the housing, and the switch itself was made of a metal frame, two terminal ends held by Bakelite, a sliding contact, a spring to keep tension on the contact, and the Bakelite slider. I cleaned up the contact and the two small divets where the sliding contact completes the circuit. Wouldn't you know it? It worked!
Everything was re-assembled and the housing was installed in the ceiling of the car.
Next up was to test again the power and ground to the switch so that we could make sure it would work once the wiring was installed. I used a power lead from the engine compartment to supply 12 volts at the driver's door jamb and once the switch at the housing was turned on the bulb lit up.
What happened next was a series of tests on both door jamb switches, the power lead from the headlight switch, and new wiring and terminals I was installing as we finished each part of the process. The picture above of the small brown box is a 12 volt source to test leads just like these. I do have a multi-meter to test ohms and continuity, but there is nothing quite as satisfying to see a light shine brightly as wiring is being tested. The video below gives more detail as to what all went into the test run and what steps I followed. In the end, I am very satisfied with the results. Maybe one of these days I can install map lights on both sides of the dash so that a light will shine on the floorboard as well.