1951 B3B 1/2 Ton PU - Gauge of wire when converting to 12volt

[Bluesmann9]

He everyone.  I am a new member to the site.

My question is, in your experience, is it okay to use the gauge of wire that is listed in the B3B wiring diagram when converting the electrics to a 12 volt negative ground? 

I am completely restoring the truck and will soon be ready to rewire.  I have the B3B wiring diagram but am wondering what you folks have to say about the wire gauge for this conversion.

Thanks in advance for sharing.  Glad I found this site.

Terrence

[Los_Control]

That will work fine for you, 6 volts actually require a heavier gauge wire then 12 volts.

So you will have a bit of over kill going on using the 6 volt wiring and going 12 volts.

You could save a few pennies and convert the wire sizes for 12 volt ... or just get on with your day and wire it up.

[bkahler]

35 minutes ago, Terrence said:

He everyone.  I am a new member to the site.

My question is, in your experience, is it okay to use the gauge of wire that is listed in the B3B wiring diagram when converting the electrics to a 12 volt negative ground? 

I am completely restoring the truck and will soon be ready to rewire.  I have the B3B wiring diagram but am wondering what you folks have to say about the wire gauge for this conversion.

Thanks in advance for sharing.  Glad I found this site.

Terrence

 

Terrence, welcome!

 

The wire gauge sizes listed in the B3B wiring diagram will be just fine.  Switching to 12 volts you'll find that the current draw is actually less than if you were running a 6 volt system.  I'm making this same conversion to my 51 B3b and followed the diagram for wire sizing.

 

You should post pictures of your truck when you get a chance.  We would all like to see them.

 

Brad

 

I see Los_control beat me to it!

Edited December 25, 2019 by bkahler

[Bluesmann9]

Los-Control and Brad.

Thanks for the reply, the information is really appreciated.

 

I'll have to put some photos together and post them as I progress further with the restoration. Currently, we are just getting ready to set the cab back onto the frame.

Terrence

[minicooper]

Hey Terrence, glad to see you here! This forum has some amazing members. Before you purchase the wiring for your project, you might consider Rhode Island Wiring Services, http://www.riwire.com, for the wiring harness(s). Even though they’re a bit pricey, I’m extremely happy with the period correct wiring, proper gauges, color coding, lengths and a bonus is that all the proper connectors are done. I believe that a forum member (gdad1951) provided the specs to them to make the harnesses.

 

-roland

 

 

 

 

 

 

 

[Bluesmann9]

Minicooper,

Thanks Roland. That's a good lead, I'll check it out.

Terrence

[JBNeal]

Allen Parkhurst's and grey beard's notes on wiring harnesses

additional information - Modified Wiring Diagram with Headlight Relays + Turn Signals

 

if you are dedicated to 12V conversion, might as well size the wiring for the loads...applying Ohm's Law, this doubled voltage increase reduces the current by half; ergo, the wire diameter can be reduced by half...this should give a lighter weight wiring harness, and cost a little bit less $$$.  From one of the wire gauge charts I found online, the 16ga can be replaced with 22ga, but I wouldn't recommend going any smaller than 18ga for durability.  So I reckon the original 6V 16ga, 14ga and 12ga can be replaced with 12V 18ga; the 10ga can be replaced with 16ga, etc.

[1949 Wraith]

I just made up a wiring harness for my '51 using Allan Parkhurt's notes, lots of excellent information. I have a 12 volt conversion and used all the original gauges, plus I added a small fuse panel and some relays.

[Bluesmann9]

JBNeal and 1949  Wraith,

Thanks for the information and insight.

I really appreciate how very helpful all of you fellows have been. I'll be moving forward with the rewire portion of this project soon.

Wishing everyone a good New Year. Stay safe.

Terrence

Edited December 26, 2019 by Terrence

[ggdad1951]

Welcome!  Thicker wires better.  Less resistance!

[B1B Keven]

Great source for your project.

 

https://enginebarn.myshopify.com/

 

[CO54]

Welcome to the forum.  Thicker is better, depending on your wiring skills and desire for original colors, there a plenty of universal wiring kits available with fuse box, relays, etc.  They also have generic wiring diagrams to assist. 

[RobWood]

On 12/25/2019 at 7:04 PM, JBNeal said:

Allen Parkhurst's and grey beard's notes on wiring harnesses

additional information - Modified Wiring Diagram with Headlight Relays + Turn Signals

 

if you are dedicated to 12V conversion, might as well size the wiring for the loads...applying Ohm's Law, this doubled voltage increase reduces the current by half; ergo, the wire diameter can be reduced by half...this should give a lighter weight wiring harness, and cost a little bit less $$$.  From one of the wire gauge charts I found online, the 16ga can be replaced with 22ga, but I wouldn't recommend going any smaller than 18ga for durability.  So I reckon the original 6V 16ga, 14ga and 12ga can be replaced with 12V 18ga; the 10ga can be replaced with 16ga, etc.

Is this all the same wiring for 12v?

[RobWood]

Also has anyone ever done something like this but used a fuse block mounted to the firewall?

[Todd B]

Yes. My semi has a fuse block. The only way my electrician would do it

[bkahler]

9 hours ago, RobWood said:

Is this all the same wiring for 12v?

Rob,

 

I used Allen's and Grey Beard's and built my wiring harness.  Their information was invaluable.  One of these days I need to upload my information to this site.  I opted to kept the wire sizes the same as required for 6 volt even though I'm switching to a 12 volt system.  

 

My logic was if I ever have the desire to switch back to 6 volts then no changes need to be made to the wiring.  Also, it doesn't hurt to oversize the wiring which is the case when you switch to 12 volts.  In this case too large is better than too small

 

Brad

[RobWood]

On 4/1/2020 at 7:29 AM, bkahler said:

Rob,

 

I used Allen's and Grey Beard's and built my wiring harness.  Their information was invaluable.  One of these days I need to upload my information to this site.  I opted to kept the wire sizes the same as required for 6 volt even though I'm switching to a 12 volt system.  

 

My logic was if I ever have the desire to switch back to 6 volts then no changes need to be made to the wiring.  Also, it doesn't hurt to oversize the wiring which is the case when you switch to 12 volts.  In this case too large is better than too small

 

Brad

 

My truck was semi switched to 12v basically a alternator and 12v bulbs and that's it. I have the schematics from Dave Erb and the CAD drawings that have been done but these are for a stock rewire and I would like to add a fuse block to the firewall and wire everything fused.

[bkahler]

On 4/9/2020 at 5:44 PM, RobWood said:

 

My truck was semi switched to 12v basically a alternator and 12v bulbs and that's it. I have the schematics from Dave Erb and the CAD drawings that have been done but these are for a stock rewire and I would like to add a fuse block to the firewall and wire everything fused.

 

I thought about adding fuses when I was building my new harness and couldn't get past the fact that the wiring had lasted 50 years and hadn't shorted out so to keep things simple I just decided to put back what came out.  Also, I think the quality of the wire sheathing is definitely better than it was 50 years ago so I guess I have my fingers crossed

 

Brad

 

[Radarsonwheels]

Mine currently has a modern fuse box on the driver’s kick panel but when I still had the flathead I used two 20 amp breakers like you’d find on a harley. They are great because when they trip you can turn off the power and they reset after a few seconds. 
 

I’ve been far from home at night looking for a gas station that had tube fuses (blade fuses too at different times) and I’d much rather just tape up a short to get home