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Triumph Repair/67 TR4-A headlight and directional switch wiring


Howard, I have a 1967 TR4-A build dater is actually 66 shipped to US in 67 and sold as 67. I have recently replaced headlight and directional switches but think I mixed up wiring. The color wire diagram I have is a little different than the wiring in the car. The wires from the headlight switch are red/green stripe, blue/white stripe, blue, brown and brown/blue stripe. At the harness I have red/green stripe, blue/white strip with dbl.connector, blue, and brown/blue stripe with double connector. If I match like wires to each other it leaves the solid brown having to go to either of the 2 possible dbl. connectors but don't know which one. The brown/blue stripe at harness is constant power.
On the new directional switch I have green/brown stripe, green/white stripe and blue/red stripe (which on the original switch was gree/red stripe. At the harness I have green/white st, green/red st, green/brown st and green/brown is ignition switch hot power. Want to confirm wiring so as not to burn out either of the new switches as one took me 2 1/2 months to get from back order. Appreciate any help you can provide.

Hi Bill,

Some replacement switches that come with a short harness often don't match the color code of the car's original colors or diagram. So often I have had to check the function of each wire on a replacement switch to see what it does and then connect it to the car.

For example, the light switch gets it's power from the ignition switch by way of a brown w/blue stripe to the #4 pin on the switch. Power out to the dimmer switch leaves pin #8 and a Blue wire. Power out to the tail lights etc leaves the light switch by pin #7 by a Red w/green stripe wire on to the fuse box on fuse #A-1 position. This is on the rectangle switch but little difference on the later round switch just the pin numbers.

The dimmer switch gets power in by the Blue wire and out to the high beams and the high beam indicator by Blue w/white tracer wires and to the Low beams by Blue w/Red tracer wire.

It is also possible that the car had a harnes change too so that makes it more important to test which wire does what rather then trying to match color coades.

Working in dealerships I was forced to make up a power test lead. I put a inline fuse in my test lead with a jumper around the fuse with a door buzzer and an inline light. This way I could use my test lead as the power source while testing circuits. If I accidently connected to a shorted circuit it would not burn up the harness but just blow my fuse and then my buzzer would go off and the light would come on giving me an audio and visual warning that my test circuit was shorted and I thus protected the car harness whill working on it. This was most usefull working on Italian cars as their wiring never matched their wiring diagrams. The only times I had to use it on British cars is when aftermarket harnesses or switches were installed and nothing matched.

It sounds like that is what you are facing. So you need to make up a fused (or circuit breaker) test lead and take that and a 12v test light and either masking tape or such to mark what each wire does. For example take a fused test lead and connect it to a power source and touch the Blue w/white tracer wire and the high beams should come on. Then label that wire as such and continue on.

As for the turn signals, the flasher unit should receive power from the fuse box via a plain green wire. Flashing power should go on to the turn signal switch via a green w/brown tracer wire and the other wire on the flasher unit should be a light green w/purple wire to the indicator light. leaving the turn signal switch should be a green w/white tracer to one side and a green w/red to the other side. (the Bentley service manual has their diagram wrong on the turn signals)

By checking the function of wires and labling them yourself you can get it corrected no matter what color the wires are.

The color coding of Lucas wiring has been very consistant over the years. It has been the aftermarket switchs and harnesses that have gotten it all messed up.  

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Howard M. Fitzcharles III


Triumph TR-4 up & Spitfire, and Engine theory


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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