found converting a stock positive earth Triumph electrical system
to negative earth to be surprisingly easy. This conversion allowed
me to connect a radio to my electrical system.
Only three items on a stock positive earth TR3 electrical system
care what the polarity of the system is, the ammeter, coil and
First I disconnected my battery cables and checked them carefully
for wear. I cleaned the terminals and the cable connectors. Next
I turned the battery around so that the cables would reach the
proper terminals. Besides checking the battery cables and cleaning
their connections at both ends, I also checked the cable between
the engine and frame. This cable provides a good ground for the
starter motor and the spark plugs.
The steps I took to do the conversion:
- Disconnected and removed the battery. This was a good time
to clean out and repaint the battery tray.
- Switched the leads on the ammeter. The ammeter has two connecting
clips. I Just moved the wires from one side to the other.
- Switched the low voltage leads on the coil. I disconnected
the leads, loosened the clamp on the coil holder, rotated the
coil 180 degrees and reconnect the wires. That preserved the
- Disconnected the small wire on the generator. The connection
post is labeled F or field.
- Placed the battery back into the battery tray in the opposite
direction as it was sitting. Reattached the hold down.
- Connected the clean ground connector to the negative terminal
of the battery. Note: The terminals are different sizes.
You may have to replace the connectors or you may be able to
open one up and close the other enough to fit.
- Disconnect the wire at terminal "F". Take a length
of insulated wire and connect one end to the battery's positive
terminal. Touch the other end of the wire to the field (F) terminal
of the generator a couple of times. This generally produces
a spark. Remove the wire from the battery. This operation repolarizes
the generator. Note: The "F" may be hard to
see on the generator so you can do these steps on the wire at
the voltage regulator "F" terminal.
- Reconnected the wire I previously disconnected from the field
(F) of the generator
- Attached the battery cable leading to the starter solenoid
to the positive terminal of the battery.
I was done
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