Triumph Repair: spitfire tail lights

Question
QUESTION: Everytime I turn on the headlights, the fuse to the tail lights blows out but the head lights stay on. Even when I unplug the tail lights and then turn the switch on the for the lights it still blows out the fuse for the tail lights. Does that make sense?  How do I correct this problem?

ANSWER: Hi Bob,

It sounds like something is wired wrong. Tell me what year Spitfire it is and I will see if I have a diagram to look at and maybe unscramble the problem.

Howard

---------- FOLLOW-UP ----------

QUESTION: Howard,
My Spitfire is a 1979.  Also the pull out knob and bulb on the emergency flasher is missing.  Could that also be part of the problem?  Thanks for your help!
Bob

Answer
Hi Bob,

The 79 Spitfire has only one fuse for all of the parking, front and rear and license lights and side marker lights and all of the interior lights. (Every light powered by a red wire)
There is no separate fuse for the tail lights.

Look on the fuse panel and you should see a lot of plain red wires on one fuse. All parking and running lights and all interior lights are on that one fuse which has just about all the plain red wires on the car.

If that is the fuse that is blowing, you need to get a circuit beaker of about 35 amp and make a test lead out of it. Remove all of the outgoing wires (red wires) off of the fuse. Attach the circuit breaker across the two terminals that connected to the fuse. Now just touch each red wire one at a time to the out going connection. Each will light a light somewhere so each time you connect a single red wire to the terminal walk around the car and look at your instrument lights to see what that red wire connects to. Either put a piece of tape on that wire to ID it or if it did light a light up ok you can attach it to the fuse trminal and leave it there.

Soon while testing each red wire you will find out that one of them pops the circuit breaker and that is the shorted circuit. Put a piece of tape on it and place it out of the way and connect all the other red wires up to the fuse terminal. Now walk around the car and see what lights are not lit up, don't forget to check the instrument lights and interior lights.

Which ever lights are not lit up is the shorted circuit. Now you need a wiring diagram to see where that red wire goes. I usually start at the bulb sockets and that light wire connection.
Here you will need either a powered test light or an ohm meter to start testing the wiring to each of the lights that don't work. This is a 100% fix rate procedure and if you follow what I outlined you can not fail to find the short.

Most all auto parts stores have the circuit breakers and wire and clips to make your tester. They also may have a powered test light or an ohm meter. If they don't have the powered test light or an ohm meter you can get one at Radio Shack. None of this test equipment is expensive and can be used the same way on every brand and model car in the world.

The most difficult short to locate will be a short in the wiring harness. But that is the more rare one too. Most are at a light socket or the connection to the light socket.

look in your owners manual for a wiring diagram or let me know and I will post one on my web site for you to copy.

Let me know what you find.

Howard