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TR4/4A TR4a positive earth to negative cut over?

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There is a TSB titled "NEGATIVE GROUND VEHICLE SYSTEM/TR-4A NEGATIVE GROUND", dated April 15, 1965. It stops short of saying that all TR4A were negative ground, but does give the implication.
 
Geo Hahn said:
My Piggot book simply says 4s were + earth, 4As were - earth.
Click to expand...
Mine has a comment that a few 4As may have been positive ground. ISTR someone saying his car had been delivered with positive ground, tho that doesn't prove whether it was built that way or converted (perhaps accidentally) by the dealer.
 
I don't know... my 66 had positive ground when I got it in 1980. I doubt that anybody had switched it over.

Dan B
 
My 67 4A which I've owned for 5 months is +ve ground. pretty sure it's always been that way. I want to convert it so that I can install a modern stereo.
 
The conversion is really easy, assuming no electronic devices have been added.

Disconnect the battery, swap the connections at the ammeter and coil, reconnect the battery with the opposite polarity, and polarize the generator. That's all.

Probably the easiest way to polarize the generator is to pull the wire off the 'F' terminal at the control box, and touch it to the 'A' or 'A1' terminal momentarily. Some small sparks are normal. Then connect it back to the 'F' terminal and you should be good to go.
 
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