Triumph Repair: Spitfire 1500 Electrical failure, bright sun light, fuse box

Question
QUESTION: I have a 1980 Spitfire 1500 which keeps suffering from electrical failure, I can be driving along & all the electrics will fail for e.g.Brake lights, indicators, fuel guage, temp guage & rev counter. This will happen intermittently throughout driving the car. Any ideas????Thanks

ANSWER: Hi Ashton,
Since you didn't say that the engine cut off you need to just clean all the contacts in the fuse box. And be sure all the fuses are tight in each holder.
Howard

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QUESTION: Thanks for the reply but I did this. If it was the fuses why would all electrics fail at once and come back on when switching the ignition on and off. This is a very frustrating and unsafe fault so any help would be greatly appreciated.

Answer
I learned a long time ago to forget symptoms when trying to correct an electrical problem. Testing is the only method to be sure what is wrong.

Pick ONLY one of the circuits that is failing (preferably a simple one) Take your wiring diagram and look at that circuit and determine where the power is originating from. Fuse box is a good place to start. Since your problem is intermittent and not totally failed you need to SEE where the failure is at the time of failure (It is no use testing a circuit when it is working).

Here is how to catch it. Take a 12v test light and connect it to the power source of the circuit that fails and run extra wire out from under the hood and place the light where you can see it. (I usually put it under a wiper arm with a piece of cardboard taped over it to shield it from the sun so I can see it even in the bright sun light. In your case where several circuits are failing you need to tap into the wire that feeds the power to the fuse that all the items are failing on. The method most mechanics do this is to run a straight pin into that wire close to the fuse box and connect to the pin and tape it up so you don't get a short and burn the car to the ground.

Now you have a visual of power to that fuse. If when it fails you still have power on your light than you know it is the fuse box. If your test light goes out then you know for sure it is the power to that fuse. So you look on the diagram and see where that fuse gets it's power from. If it is the Ignition switch (unlikely because you probably would have lost ignition at the time of failure.

I keep a test light I have made up with clips on each end for this purpose and have to use it often.

Howard