The Ford Barn

Woodie1 · 11-12-2021, 01:23 PM

We have a 39 Deluxe that is new to us. I noticed the battery has a negative ground. Should I change it? If so, what else would have to be dealt with & how? Thanks.

JSeery · 11-12-2021, 01:54 PM

Need to check out a few things first. Is it 6v or 12v? If 12v it is probably neg grounded. If 6v, it will take a little more checking. What type of coil does it have, as in attached to the distributor or a "can" coil? What type of generator does it have?

Woodie1 · 11-12-2021, 02:45 PM

The battery is a 6 volt. It has the original coil mounted on top of the distributor & the generator is the original style. It has a voltage regulator on the firewall.

J Franklin · 11-12-2021, 04:29 PM

If the polarity was reversed properly for what ever reason, you won't need to worry about it. what does the previous owner have to say?

cas3 · 11-12-2021, 04:50 PM

turn on the headlights, and see which way the ammeter goes. charge? or discharge ?

Woodie1 · 11-12-2021, 06:38 PM

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The charging is proper right now. I had read that the electrical system doesn't function as well with the negative ground. I haven't said anything to the previous owner. They put a new battery in the car in June & I'm guessing they didn't know it was reversed or maybe it was when their dad was still able to drive it.

cas3 · 11-12-2021, 07:05 PM

If the ammeter does not read backwards, the car has been "fixed" to negative ground

paul2748 · 11-12-2021, 10:22 PM

Nothing wrong running a negative ground 6 volt

supereal · 11-13-2021, 04:52 PM

As the stock ground is positive, there was either a mistake made by a previous owner, or the installation of an accessory, such as an electric fuel pump, which is sensitive to the polarity. We see it where aftermarket radios are installed, etc.

Woodie1 · 11-13-2021, 08:49 PM

I was curious about the radio too. It hums & looks very nice but the dial will not turn. I didn't know if polarity would mess the original radio up or not.

rotorwrench · 11-14-2021, 11:25 AM

The old radio sets with the electro-mechanical vibrators are not polarity sensitive. The ignition coil is polarity sensitive. The leads to the primary should have been switched to get full high tension energy output from it. They are generally marked "DIS & SW" for distributor and switch. A person can check the output with one of the Nu-Rex testers or carefully with a lead pencil. If marked + & - then it can be connected per normal 12-volt system standards. Negative side to distributor and positive to ignition switch. A negative ground system would have negative connected to the ignition switch and positive to the distributor. I'd still check the polarity though.

If a person wanted to put it back to OEM, the coil would have to be checked for polarity and the generator would have to be polarized for positive ground by flashing the field. Some of these old models had a volt meter instead of an ammeter. If it has an ammeter then it depend on whether it is a shunt type meter or an induction type meter as to what a person has to do to get the correct indication from the meter. Shunt types have two terminals on the back and induction types have a metal loop that the wire travels through to give an indication. Terminal can be swapped or the wire can be changed from one end of the loop to go through the other end depending on type.

Someone may have converted or someone just connected it wrong. The battery terminal clamps are different sizes so that should be apparent unless someone put new 12-volt type cables on the car recently.

11-12-2021, 01:23 PM	#1
Woodie1 Senior Member Join Date: Mar 2011 Location: W. Mich. Posts: 471	Battery polarity We have a 39 Deluxe that is new to us. I noticed the battery has a negative ground. Should I change it? If so, what else would have to be dealt with & how? Thanks.

11-12-2021, 01:54 PM	#2
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: Battery polarity Need to check out a few things first. Is it 6v or 12v? If 12v it is probably neg grounded. If 6v, it will take a little more checking. What type of coil does it have, as in attached to the distributor or a "can" coil? What type of generator does it have?

11-12-2021, 02:45 PM	#3
Woodie1 Senior Member Join Date: Mar 2011 Location: W. Mich. Posts: 471	Re: Battery polarity The battery is a 6 volt. It has the original coil mounted on top of the distributor & the generator is the original style. It has a voltage regulator on the firewall.

11-12-2021, 04:29 PM	#4
J Franklin Senior Member Join Date: May 2010 Location: Oregon Posts: 5,961	Re: Battery polarity If the polarity was reversed properly for what ever reason, you won't need to worry about it. what does the previous owner have to say?

11-12-2021, 04:50 PM	#5
cas3 Senior Member Join Date: Jan 2011 Location: sw minnesota Posts: 4,571	Re: Battery polarity turn on the headlights, and see which way the ammeter goes. charge? or discharge ?

11-12-2021, 06:38 PM	#6
Woodie1 Senior Member Join Date: Mar 2011 Location: W. Mich. Posts: 471	Re: Battery polarity Sponsored Links (Register now to hide all advertisements) The charging is proper right now. I had read that the electrical system doesn't function as well with the negative ground. I haven't said anything to the previous owner. They put a new battery in the car in June & I'm guessing they didn't know it was reversed or maybe it was when their dad was still able to drive it.

11-12-2021, 07:05 PM	#7
cas3 Senior Member Join Date: Jan 2011 Location: sw minnesota Posts: 4,571	Re: Battery polarity If the ammeter does not read backwards, the car has been "fixed" to negative ground

11-12-2021, 10:22 PM	#8
paul2748 Senior Member Join Date: May 2010 Location: Midland Park, NJ Posts: 3,981	Re: Battery polarity Nothing wrong running a negative ground 6 volt __________________ 48 Ford Conv 56 Tbird 54 Ford Victoria

11-13-2021, 04:52 PM	#9
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: Battery polarity As the stock ground is positive, there was either a mistake made by a previous owner, or the installation of an accessory, such as an electric fuel pump, which is sensitive to the polarity. We see it where aftermarket radios are installed, etc.

11-13-2021, 08:49 PM	#10
Woodie1 Senior Member Join Date: Mar 2011 Location: W. Mich. Posts: 471	Re: Battery polarity I was curious about the radio too. It hums & looks very nice but the dial will not turn. I didn't know if polarity would mess the original radio up or not.

11-14-2021, 11:25 AM	#11
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,426	Re: Battery polarity The old radio sets with the electro-mechanical vibrators are not polarity sensitive. The ignition coil is polarity sensitive. The leads to the primary should have been switched to get full high tension energy output from it. They are generally marked "DIS & SW" for distributor and switch. A person can check the output with one of the Nu-Rex testers or carefully with a lead pencil. If marked + & - then it can be connected per normal 12-volt system standards. Negative side to distributor and positive to ignition switch. A negative ground system would have negative connected to the ignition switch and positive to the distributor. I'd still check the polarity though. If a person wanted to put it back to OEM, the coil would have to be checked for polarity and the generator would have to be polarized for positive ground by flashing the field. Some of these old models had a volt meter instead of an ammeter. If it has an ammeter then it depend on whether it is a shunt type meter or an induction type meter as to what a person has to do to get the correct indication from the meter. Shunt types have two terminals on the back and induction types have a metal loop that the wire travels through to give an indication. Terminal can be swapped or the wire can be changed from one end of the loop to go through the other end depending on type. Someone may have converted or someone just connected it wrong. The battery terminal clamps are different sizes so that should be apparent unless someone put new 12-volt type cables on the car recently. Last edited by rotorwrench; 11-14-2021 at 11:57 AM.