reverse polarity on starter motor

[mklotz70]

This came up in Fisch's '59 thread...I didn't want to hijack or trample on his thread, so I started this one.

 

This is in regards to whether or not the starter motor (and wiper, fan, etc) would turn backwards if you switched the battery connections from neg ground to pos ground......or in Scott's case, pos grd to neg grd. I stated that they would spin the same direction. I would hope so or my NL has been running backwards for the last 2 years :) Anyway....this comment was brought into question. I'm not that bright....so off to the shop to prove it one way or the other. In my pj's no less :)

 

 

[Charlie69]

I chuckled when I read what Six Shooter wrote "I work with automotive electronics, this includes automotive electric motors.

 

Connect a starter, electric fan, or any other automotive or for that matter non-automotive DC motor in a "reversed polarity" and it will indeed run in the opposite direction than it would wired in "forward polarity".

 

It is only (most) AC motors that do not care about polarity.

 

BTW, those "hobby motors" you speak of also use windings, open one up sometime.":lol::lol::lol:

 

Mike you got a good one here.

[thisismatt]

You can't argue with some people...can't see the forest for the trees.

[bonvo]

lmfao owned

 

he was right about electric fans though

[DanielC]

Some electric motors will reverse rotation, and some motors will run in the normal direction, with a polarity switch.

Many modern starters use magnets for the field, and will reverse rotation if the polarity is switched

Older starters used field coils, and may not reverse rotation.

I have an old Ford 8N tractor. It started out life as a 6 volt positive ground electrical system. I converted it to 12 volts, using an internal regulated GM alternator. The electrical system is now negative ground. The starter did not have to be changed or modified.

[mklotz70]

I'm not trying to pick on the guy...I'm sure he has a reason for making his statements. I wanted to show what I was talking about. I'm pretty sure I made a similar comment several years ago and got "corrected". I then went and did a bunch of research on the subject. All mine was limited to older stuff. Mainly regarding conversions from pos ground to neg ground......which is what the subject was on Fisch's thread. The guys that have been on here as long as me, know that I make mistakes....so this was to prove it to myself as much as anything else. I just want to make sure that the info that goes out is correct.

 

As DanielC said(good to see you again...been awhile :) ) ...he's probably referring to newer stuff. Magnet technology has come a long ways. I was referring to the heater fan motor, but cooling fans probably do have permanent magnets. I have felt a couple that had the "detent" feel to them when spun.

 

SixShooter didn't say if he works on new or old stuff....I'm gonna guess newer stuff. Heck...I can troubleshoot the older wiring easy enough.....but Cadillac started putting small computers through out they're cars about 10 years ago. There's like 26 of them?! My meter and I won't get very far with that!!

[Charlie69]

Good point Mike & DanielC about new and old electrical systems. I was laughing about this because I have converted dozens of positive ground vehicles and equipment to negative ground and never had a problem but then it was all old stuff. I am not aware of any new stuff that is positive ground, although I am sure there probably is some out there. All my experience has been with stuff that is older than me which would make it manufactured before 1957. I am sure that the newer electrical systems are way to advanced for my skills. I pretty sure that there is very little 6 volt to 12 volt conversions done now.