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TR2/3/3A TR3Positive ground conversion

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Jedi Knight
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I just read the VTR page about converting to + ground.
Straight forward enough,but I think I am also going to reverse leads on Windshieeld Wiper motor and heater fan so they dont run backwards.The motor leads,I think ,are isolated from frames.
isnt the starter motor also an issue?
Any thoughts appreciated.
Thanks
Tom
 
You don't need to do that. The motors won't run backwards if you change earth polarity.

An electric motor will reverse direction of rotation if you reverse the current flow through EITHER the armature or the field. When you reverse the earth polarity, you will change the direction of flow through BOTH the field and armature, so you're back where you started.
 
If you have the self-parking wiper motor, then it does ground through the frame as well as the lead to the switch on the panel. Trying to reverse the leads will cause a short.

Later wiper & heater motors used permanent magnets for the field, and so will run backwards if the polarity is reversed. But the wiper, heater, and starter motors on the TR3 all used wound fields, meaning they run the same way regardless of polarity (just as John describes).
 
You also want to be aware that if you have a Pertronix dissy (or other) it will need to be replaced with a negative ground version. No way around that one that I know of.
 
gecoughenour said:
Do the "modern" gear-reduction starters also have wound fields so they are also "bi-polar"?
Click to expand...

It depends, some do, some don't. The Denso unit in my TR3 has permanent magnets.
 
I was thinking you could easily check if the field was a permanent magnet by seeing if the case is magnetic when the battery is disconnected. Is that right?
 
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