12 volt positive earth 46 coupe

Brendan1959

Brendan1959

Member
Hi
looking for some advice, I thought my recently purchased 46 coupe was still 6 volt and running as a total loss system on a 12 volt battery. I bought a alternator, bracket coil and a electric wiper kit. someone had installed some sort of voltage dropping unit to supply the instruments. I was planning on a rewire as it all looked a bit dodgy. I had checked the volts at the battery with the motor running, no charge. I was just about to start ripping in to it when I thought I would test the battery voltage again, started it up put the meter on the battery no charge, upped the revs a bit and up came the volts. Good news I thought I can stay with the generator. There is no vacuum unit for the wipers hence the vintique wipers conversion. Has anyone used one of these with positive earth?.

Brendan
 

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Must motors will run on + or - gnd. They just run backwards. Don't see any problem with a wiper motor. Also a lot of stock gauges don't operate on 12V so they installed a 12-6V reducer
 
Most motors will run positive or negative ground, with no problem. Very rare for one to run backwards when you swap polarity.
Ask vintique, incase there's something electronic in the wipers that's polarity sensitive. If there is you'd have to isolate the wipers from ground, might be tricky, I'd be surprised if there was.
Martin.
 
Hi Brendan, I have a 46 business coupe. It was originally a New Zealand car. I bought it last November.

I am running 6 volt positive earth. I bought one of the electric wiper kits but haven't fitted it yet.

I'm pulling the motor at the moment. Once I get that back in I'll install the wiper kit. I'll let you know how it goes.

Are you going to Dubbo?
 
Thanks all
I bench ran it positive and negative ground and it seems to be ok. I did email the manufacturer a week or so ago but got no reply.
Brendan
 
scooder said:
Most motors will run positive or negative ground, with no problem. Very rare for one to run backwards when you swap polarity.
Ask vintique, incase there's something electronic in the wipers that's polarity sensitive. If there is you'd have to isolate the wipers from ground, might be tricky, I'd be surprised if there was.
Martin.
Click to expand...
"very rare for one to run backwards"- Really?
 
Yeah really. I've never had a motor run backwards after a polarity change on a car. Wether it be wiper motor or fan motor or starter or whatever. Not saying it can't happen on any electric motor, just that it's rare on an automotive motor.
If my brain is working correctly, a permanent magnet motor will reverse if you swap the polarity. But the type found in autos is almost exclusively Not Perminant magnet type.
The heater motor used in some of the 40's era Ford's have a reversing function, but I never played with one. I believe the motor is built specifically for this function, not just a polarity swap at the switch. Maybe some one who has played with one could tell us how that motor is wired.
Martin.
 
fordor41 said:
Must motors will run on + or - gnd. They just run backwards. Don't see any problem with a wiper motor. Also a lot of stock gauges don't operate on 12V so they installed a 12-6V reducer
Click to expand...

When your backing your car up you have to stop and change the batt cables around so you can go forward. The devil made me do it. Walt
 
As it's 12V you might as well make it negative ground, Then you can use a lighter socket for things like sat nav, usb and phone charger etc. The alternator will be configured for negative earth too.

Mart.
 
Mart
I am still running what I think is the original 6 volt generator with what I think is a 12v regulator, so I dont think negative ground is possible with this setup?
Brendan
 
Dude, you said you had an alternator at first, Mart is bang on with his negative ground suggestion. I missed the alternator bit earlier, had I seen it I would have said the same, just go negative ground.
Now you say generator? What have you actually got? With this info you'll get the right answers.
For the record, any generator can be polarised (simple no tools) to work negative or positive ground.
Martin
 
Martin
I bought an alternator and bracket but hope not to fit it, so you say I can make the generator negative ground, how is it done?
Brendan
 
There are a lot of threads on the subject. Turn the battery round. Connect the battery cables. You might need to change the terminals as they are different sizes. Then you need to polarise the generator. Google it, I don't want to give duff info. (It involves flashing a wire across some terminals on the regulator - I think - google it).

You might need to reverse the terminals on your coil. not sure.

That's all that is involved. I don't think using a 6V generator on 12V is a good way to do it - again, google it, it can work, but you don't get the output you would with a proper 12V converted generator.

I have converted generators using a mix and match of old and later generator parts - it's all well documented - google is your friend.

Make sure all the bulbs have been switched over to 12V alternatives. You can use reducers or modern voltage regulators (electronic parts that cost pennys) to power the gauges.

Most importantly, do some research. Lots of info out there. If you can't find a specific answer to a question, just ask, but it is better to search for the info yourself than to just expect it to be handed on a plate for you.

Mart.
 
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Well stated Mart. I've been suggesting using Google for years. Lots of great info on the web & faster to get the info you desire.
 
scooder said:
Yeah really. I've never had a motor run backwards after a polarity change on a car. Wether it be wiper motor or fan motor or starter or whatever. Not saying it can't happen on any electric motor, just that it's rare on an automotive motor.
If my brain is working correctly, a permanent magnet motor will reverse if you swap the polarity. But the type found in autos is almost exclusively Not Perminant magnet type.
The heater motor used in some of the 40's era Ford's have a reversing function, but I never played with one. I believe the motor is built specifically for this function, not just a polarity swap at the switch. Maybe some one who has played with one could tell us how that motor is wired.
Martin.
Click to expand...

Yup. On a perm magnet motor the field windings are replaced by magnets so changing the polarity of the armature will change the rotation of the motor because the magnets haven't moved. Heater,starter and wiper motors have field windings so if polarity is reversed both the field and armature get reversed so rotation is the same. Speed control can be done by lowering the voltage to the fields.
 
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