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63 b81 how can i tell if its 24v positive ground


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I have a 63 b81 I just got I was told it is 24 volt positive ground

How can I tell.

If it has batteries in the truck look at the positive cable from a battery. If positive ground it will run to the starter motor housing. If it has a generator on the engine chances are it is 12 volt positive ground. There should be a large switch, (series parallel) between the seat under a cover. This converts 12VDC, to 24VDC used in starting. Most alternators are negative ground and I don't think any B model were originally built with an alternator unless a fire apparatus.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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A quick story about positive ground. The fire dept I run with had a 66 American lafrance in the 80s it was in a bad wreck the truck sat around for a year until they decided to rebuild it when it came back from lafrance and had all the equipment put back on it was over the truck gvw and had a positive ground lafrance never told the fire dept about that and as they put the radios and other electronics in they shorted out. They sold the truck in 1991 to a fire dept in the southern states 10 years ago the we got a random phone call asking if we owned this truck and did the pump work because the truck burned up and these people wanted to rebuild it no one ever told the people it was positive ground when they bought it and they started wiring stuff to the truck causing it to burn.

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Sure fire way is to take a meter and measure ohms from either cable to a bare sport on the frame...one will have almost no resistance, the is the "ground" whether positve or negative...

A lot of meters will pop their fuses if you apply voltage when the ohms scale is selected for a short period.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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  • 5 years later...
2 minutes ago, Trevor Flores said:

Got a positive ground Mac truck in today at my job having a tough time figuring how I can make led lights work on newer gooseneck if possible?! Any help anyone?

They make positive ground LED for older British cars and motorcycles.

"OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK"  Thomas Edison

 “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’

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