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Posted

Don, if the polarity is reversed, the motor's, including the starter will not run correctly unless the polarity connections inside the starter have been swapped over.

A 12 volt negative change would also include coil & globe changes & there will be issues with the fuel gauge.

 

You are correct in thinking there has been some changes made & without seeing the truck we are purely speculating.

Posted (edited)

Don, if the polarity is reversed, the motor's, including the starter will not run correctly unless the polarity connections inside the starter have been swapped over.

A 12 volt negative change would also include coil & globe changes & there will be issues with the fuel gauge.

You are correct in thinking there has been some changes made & without seeing the truck we are purely speculating.

 

 

 

 

will spin correctly as the DC motors in question are not permanent magnet..they are electromagnet fields

Edited by Plymouthy Adams
Posted

I have added some notes & arrows to the wiring diagram from my workshop manual.post-6688-0-92793500-1392609805_thumb.jpg

Posted (edited)

   It was me. Its my fault. I had the gauges refinished last year and wired it up wrong. I just haven't noticed it until I started having this problem. I'm the big dummy.

Edited by tom'sB2B
Posted

All good, Tom!

Best I go & start learning about my Dodge now as it needs a complete re-wire.

 

All my previous cars (with the exception of our 68 Barracuda) have been 12volt negative earth Holden's. (Aussie GM)

Posted

Don, if the polarity is reversed, the motor's, including the starter will not run correctly unless the polarity connections inside the starter have been swapped over.

A 12 volt negative change would also include coil & globe changes & there will be issues with the fuel gauge.

 

You are correct in thinking there has been some changes made & without seeing the truck we are purely speculating.

You might want to double check your suggestions as they are not correct.

Posted

I like this guys videos because he cuts to the chase. He's talking mostly about MG's but is working with a 6 volt system. 

Dig through his channel....he has a lot of good videos on basic stuff.

 

http://www.youtube.com/watch?v=PPUfQtVEJGg

 

http://www.youtube.com/watch?v=NV8FFgia7uU

 

48D

Posted

Don, if the polarity is reversed, the motor's, including the starter will not run correctly unless the polarity connections inside the starter have been swapped over.  . .

Sounds like you are not familiar with the design and construction of the generator and/or starter motor: Since the field is provided by a field coil, changing polarity of the input voltage will result in reversal of both the armature magnetic field and the field coil's magnetic field. Since both are changed the starter motor will rotate the same way as before the polarity reversal. Same holds true for the generator.

 

A modern DC motor with permanent magnet fields will be different and will reverse direction when you change the polarity of the power.

  • Like 1
Posted

Very well explained Todd!

  • 3 weeks later...
Posted

I might add that your initial test of the generator's health by removing one battery cable while the engine is running, can be a good but crude test of the generator circuit, with some exceptions.

 

First, generators (normally) don't produce enough voltage at idle to run the car. At idle, the battery is still being used to supply sufficient voltage to power the ignition circuit. 

 

If you rev the motor to around 1,000 rpm the generator should indeed be powering the ignition system, and if at that speed you remove the ground cable and the engine quits, you have a problem in the generator circuit. It may be the generator at fault, or it could be the regulator, or faulty wiring connections.

 

One reason for the move to using an alternator is that alternators provide more voltage at lower rpms than generators, therby recharging the battery during times when the engine is only turning at idle speed.

 

The movement on your ammeter when you introduce a load such as headlights, is controlled by the voltage regulator. Making sure this is the correct regulator for your generator and the intended usage (lights on all the time, never, sometimes, radio always on, no radio, heater motor, electric vs vacuum wipers, etc.) is one key to having a healthy electrical system.

 

Too many people install 12 volt systems thinking they are 'better' when they never had a properly operating 6 volt system in the first place.

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