24v light system, 12v engine question

[kendelrio]

All-
Was flagged down Sunday by a retired man while tooling around in the M715 by a gentleman who owns a M725 (pictured below). He has the OG 24v generator etc, but has repowered to a 350.

His electrical system setup has me baffled. He has a 12v alternator on the 350 that charges a single battery for the engine, but is also running the OG generator to charge a 24v system and two batteries for his lights.

Simplest question:
How would one go about changing the engine to 24v or would it be easier to change his lights to 12v in order to combine the electrical systems and simplify it.

What issues would he run into in either scenario? I've volunteered to help him get her run and I want to do the best work I can.

 

[Barrman]

You just opened THE big can of worms for M715 modification Ken.

The M113 APC used a Chevy 283 V8. The 24 volt distributor for those vehicles will fit any small block Chevy. I have never seen one of these distributors in person. I have seen them for sale every so often though. This is the most military correct and kind of easiest way to put in a V8 and keep the entire truck 24 volts.

Other people just put a resistor between the 24 volts and the 12 volt ignition coil. Along with an easily available 24 volt starter of course.

While others use a 24-12 volt reducer to do the same thing.

Another option is the CUCV 24/12 volt hybrid system. It works very well and is well documented. You just have to keep track of what is 24 volts and what is 12 volts.

Personally I like the CUCV set up if you want to keep anything 24 volts on the truck. If you understand it, it is really very simple with huge TM support.

The resistor/24 to 12 reducer method is the easiest and cheapest. However, at one of our Texas gatherings 15 or 20 years ago someone with a 24 volt M715 running a Chevy straight 6 engine on 12 volts through a reducer had his engine just turn off. The reducer had failed and his coil burned up. Thankfully he had anticipated this and had a spare reducer and coil on him. 30 minutes of work and all was well again for that weekend.

I don’t like that uncertainty personally and converted my M715 to 12 volts when I put the 396 Big Block in it back in 2005. The solid state blinker works on 12 volts once the bulbs are changed. I could slave any of my other trucks or be slaved though. So when I swapped over to the 6.2 in 2013 I used the CUCV 24/12 system and really like that. It works for me.

Does this answer your question at all?

 

[kendelrio]

It certainl

You just opened THE big can of worms for M715 modification Ken.

The M113 APC used a Chevy 283 V8. The 24 volt distributor for those vehicles will fit any small block Chevy. I have never seen one of these distributors in person. I have seen them for sale every so often though. This is the most military correct and kind of easiest way to put in a V8 and keep the entire truck 24 volts.

Other people just put a resistor between the 24 volts and the 12 volt ignition coil. Along with an easily available 24 volt starter of course.

While others use a 24-12 volt reducer to do the same thing.

Another option is the CUCV 24/12 volt hybrid system. It works very well and is well documented. You just have to keep track of what is 24 volts and what is 12 volts.

Personally I like the CUCV set up if you want to keep anything 24 volts on the truck. If you understand it, it is really very simple with huge TM support.

The resistor/24 to 12 reducer method is the easiest and cheapest. However, at one of our Texas gatherings 15 or 20 years ago someone with a 24 volt M715 running a Chevy straight 6 engine on 12 volts through a reducer had his engine just turn off. The reducer had failed and his coil burned up. Thankfully he had anticipated this and had a spare reducer and coil on him. 30 minutes of work and all was well again for that weekend.

I don’t like that uncertainty personally and converted my M715 to 12 volts when I put the 396 Big Block in it back in 2005. The solid state blinker works on 12 volts once the bulbs are changed. I could slave any of my other trucks or be slaved though. So when I swapped over to the 6.2 in 2013 I used the CUCV 24/12 system and really like that. It works for me.

Does this answer your question at all?

It certainly gives me something to chew on.

I guess I'm just going to convert the truck to 12v as he wants to sell it and I don't think he will be investing any serious money into it. I just want to get it solid electrically. What would be the simplest way to do it? It the engine side is already 12v. Wouldn't it just be a matter of changing bulbs to 12v also?

 

[Barrman]

Yes, making everything 12 volt and him including a bag of 24 volt bulbs with the sale is cheapest and easiest.