12V conversion

[dgrinnan]

I have done a 12v conversion before but not on a vehicle with a positive ground system.  Do you need to do anything different?  Can you convert to 12v and stay positive ground?   I know about all the other stuff that is needed.  Light bulbs, ballast resistor, gauges.

Edited August 15, 2022 by dgrinnan

[Young Ed]

You could but you'd be defeating most of the point in converting because all the 12v electronics are neg ground 

[dgrinnan]

So nothing special has to be done (other than the normal conversion stuff)?  I can just reverse polarity when I do the conversion and go to negative ground? 

[kencombs]

If you retain the ammeter,, you'll need to reverse the connections in order for it to show charge correctly.  Other than that the normal 6to12 stuff.

[dgrinnan]

Thanks for the feedback.

[LMBoise]

I just made the conversion on my ‘48 Pilothouse. This link to a previous forum post provides a great electrical diagram. It is from a later model, but same approach. 
 

https://p15-d24.com/uploads/monthly_2017_05/590a5990132b5_12voltwiringdiagram.jpg.0b959fe5a0dcc3ec6fe96b25c7c6dc92.jpg

 

 

[Sniper]

Most commonly available 12v alternators are negative ground, which can't be changed.  I suppose there might be some 12v positive ground ones out there, but they aren't cheap.

[dgrinnan]

I am not against switching to negative ground.  I just didn't know if it required anything special.  I appreciate every ones help. Switching the altimeter polarity is easy.

[ggdad1951]

4 hours ago, dgrinnan said:

I am not against switching to negative ground.  I just didn't know if it required anything special.  I appreciate every ones help. Switching the altimeter polarity is easy.

ALTIMETER?  Now THAT is a fancy truck!  ?

 

(assuming autocorrect error)

[Mike Fix]

No, that wasn't autocorrect. That is the new marketing term for an ammeter on a vehicle with an alternator. "Why just have an old tired generator ammeter when you can have the new, high-powered alternator Altimeter! Soar to new heights without ever leaving the ground!" ?

[Mike Fix]

"Coming soon to a dealer near you."

[dgrinnan]

[Los_Control]

Sounds like you have it all under control. About the only issue with switching from positive to negative ground would be a radio.

You would not be able to use a stock +ground radio with a -ground system.  ..... Betting your truck does not have one, is possible though.

 

The starter does not care.

Heater motor wont care but will spin really fast on 12v.  You can reduce it down to 6v or replace the motor for $10-$15.

Wipers? good chance you have vacuum?

 

I have the exact replacement tank & fuel sender sold for your 1947.

I told the lady over the phone that my truck was still 6V +ground. Wanting to be sure I got the right parts.

She told me that the sending unit & gauge did not care about the voltage or ground.

 

So I'm going on what the supplier told me when ordering parts for my 1949.

[lostviking]

Me thinks she would be wrong. The gas gauge cares.

 

Tim

[Veemoney]

My 47 WC has the stock thermostatic gauge, I am running 6v negative ground in my truck with a 6v alternator. My fuel gauge has a terminal for power from the ignition switch and terminals 1 and 2 that connect to their respective terminals 1 and 2 on the sending unit. It is working as it should. There is another style fuel gauge that came out around 47-48 that is different from the thermostatic type made by Moto Meter.  I cannot speak to how it would work switching the polarity.  

[Adam H P15 D30]

On 8/31/2022 at 12:23 PM, lostviking said:

Me thinks she would be wrong. The gas gauge cares.

 

Tim

A Runtz resistor can be added to the fuel gauge circuit, it does not care about polarity.

I used a 60s Dart heater blower motor, it was a direct bolt in.

My clock doesn't care.  Been running on 12v for years.

[lostviking]

I did some searching because I didn't know if the gauge was measuring voltage or current. I found an excellent thread with a great explanation of how the gas gauge works.

 

https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/100645/6-12-volt-fuel-guage-sender-theory.html

Edited September 4, 2022 by lostviking