Saturday, November 15, 2014

Headlight Wiring - Plan, Participate, Prevail

So, after perusing the Internet trying to figure out how to implement electrical headlights, I finally knuckled under.  I had seen a few people use full actuators, and others who used some old Mazda Miata or Ford Probe headlight motors.  With the costs of actuators running to $200 a piece for a 4" movement (and needing one for each side), I realized I was too cheap.  I had to do the Probe conversion.

I ran to the closest junk yard, and found a mid-90's Ford Probe.  I pulled the motors and arms attached to the motors and paid about $30.  I ran home and tested them against the battery.  Woohoo! They both worked!

Next, I had to wire them up.  I didn't want to cut into the old harness at all in case I wanted to back this out some day.  So, I grabbed three spade connectors - these would plug into the current 3-prong headlight connector (the one for brights AND regular beam).  I also bought a new 3-prong connector. These would be soldered together with three wires coming off as "taps".  These three wires (one is battery negative, the other two are battery positive when the high beams are on, or the low beams) feed (via two 1 amp diodes to prevent both lights from coming on) into a 12 relay (SPDT, or Single Pole Double Throw, where when on, one is connected, but when off, another terminal is connected).  This is wired to a fuse and to a battery connection.  When the high beams or the low beams are on, it triggers the relay to power one line, and when neither are on, the relay switches back to the other.  These two feed the motor trigger signals.  A second "power" is also run to the motors, and a negative battery connection.  I tested this (test often is vital to make sure it works) via a breadboard first, with LED's to make sure I had things connected right (e.g. when one light was on, the signal light was on, and when the other light was on, the same signal light was on, but one light did not cause the third light to come on).

Once I knew I had the circuit right, I had to implement it. I grabbed a solder "bread board", and soldered everything into place.

Then, I tested it against the real lights and motors.  Success!  I threw on electrical tape to protect things, and applied epoxy to the bread board to seal it in.  When the epoxy had set, I applied more electrical duct tape to ensure it wouldn't cause other problems.

Once it was all wrapped up, I installed it, and tested it once more just to make sure it was good.  Congratulations!  Now I just need the headlight units back from the painter, and I can finish the front end of the car!  Here's my shopping list.

  • 2x Ford Probe headlight motor
  • Brackets (had to make these out of porch 4" post end caps from Home Depot)
  • 3x Spade Connectors
  • 1 3-Prong Headlight Connector
  • 2x 1 Amp Diodes
  • 1 solder board from Radio Shack
  • Wire (red and black)
  • Epoxy

If anyone wants to convert, it's not too difficult!

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