It has come time to start to wire the beast. Prior to my purchase of the truck all the wiring and lights had been stripped from it, for what reason I have no clue. The seller did provide me with a non working 24volt generator and regulator. so pretty much I need everything in the wiring and lights section.
I was reading about the older B Model Mack’s that used a Parallel Switch allowing the use of 24 volts for starting and switching to 12 volts for lights gauges etc, also charging batteries during operation. Some how it switches batteries to series then back again. This would allow me to use a universal harness and fuse block I already had for an old project and use a single wire alternator while still using the 24 volt starter. Has anyone done this ? Any Thoughts?
A little about the switch
If you connect two 12v batteries in series 24v to start the tractor then rearrange the battery cables so the batteries are connected in parallel 12v to run lights and charge from a 12v alternator you are manually doing what this switch does instantly
If I were you, I would take your orig. starter to a starter shop, and have it rewound for 12 volts, and rebuilt in the process. Add a 12v coil in the distributor, and there you go, a 12v truck.
If I were you, I would take your orig. starter to a starter shop, and have it rewound for 12 volts, and rebuilt in the process. Add a 12v coil in the distributor, and there you go, a 12v truck.
Brett
I was unaware they could do that. I will look into that. Much easier
Thanks
MVPA #32564
WAC/B&G MVT
Patriot Guard Riders
NRA Life Member
NRA Certified Instructor
GOOD MORNING,
I had a boat with a 12-71 detroit diesel eng; that was 24v start. The rest of the boat was 12v. I used a series/parallel switch. I cruised this boat up and down the east coast over to the Bahamas, and the crib. I lived 8 years on that boat, and the switch never gave me a problem.
Easy to wire and intall, its about the size of a can of dog food.
GOOD LUCK BOB
Greetings Folks,
I just saw this post tonight and thought I'd add a bit from a situation I'm involved with.To get 12V from a two 12V battery 24V system: Run a cable from the positive terminal and a cable from the negative terminal (very important,this "splits" the voltage) of ONE of the batteries and wire them to the component or to a junction or fuse block (preferred) connecting the appropriate wires of the appropriate GAUGE to handle the AMP LOAD, to the component positive/feed and negative terminals.You will have to ground the body of the component if there is no terminal such as at a mounting bolt or screw.With the junction or fuse block,you can power up the bussbar and then pull multiple feeds at 12V from there,making up a harness if appropriate.Mount the junction/fuse block in a box to avoid short circuits from items errantly contacting the live contacts.This is a good setup if you have 12V items like radios or CB's that you want to use in the 24V rig.Good luck and hope this helps,Chris.
ODUSAOK wrote:Greetings Folks,
I just saw this post tonight and thought I'd add a bit from a situation I'm involved with.To get 12V from a two 12V battery 24V system: Run a cable from the positive terminal and a cable from the negative terminal (very important,this "splits" the voltage) of ONE of the batteries and wire them to the component or to a junction or fuse block (preferred) connecting the appropriate wires of the appropriate GAUGE to handle the AMP LOAD, to the component positive/feed and negative terminals.You will have to ground the body of the component if there is no terminal such as at a mounting bolt or screw.With the junction or fuse block,you can power up the bussbar and then pull multiple feeds at 12V from there,making up a harness if appropriate.Mount the junction/fuse block in a box to avoid short circuits from items errantly contacting the live contacts.This is a good setup if you have 12V items like radios or CB's that you want to use in the 24V rig.Good luck and hope this helps,Chris.
I am pretty sure center tapping the series 24v circuit leads to unbalanced battery charging and problems down the road. A better bet would be a 24 to 12 volt transformer for those loads
Short answer here. A series parallel switch will work great, BUT those types of systems are obsolete for years, and the switches of quality are mostly gone. I'm very familiar with that system as I owned B model MACKs back in the grading contractor years. The absolute best thing you can do is go back with the original 24-volt system, more reliable and easy quality parts access. If you must change to 12-volt, best approach is to go all 12. Any way you approach this will cost some $$$ if you acquire quality components, so why not keep it simple to put in place and to maintain; that would be the original 24-volt system.
If I were you, I would take your orig. starter to a starter shop, and have it rewound for 12 volts, and rebuilt in the process. Add a 12v coil in the distributor, and there you go, a 12v truck.
Brett
Call from the starter shop They cant convert my starter to 12 volt they searched for a 12 volt armature and there are none available or ever made for that starter I asked it they could rewind it and they said nobody is doing that anymore plus they couldn’t get the field coils for 12 volt starter anyway. I guess they don’t have ability. I called Steve over VPW and asked about the starter and agreed not do able, also asked about a 12 volt coil that drops in the military distributor and he told me he knows of no such coil. Spoke to Charles over M Series Rebuild LLC in North Carolina he said he has a 12 volt starter available $400.00 and at one time there was a drop in 12 volt coil out there but hasn’t seen one in years. He said I should just bite the bullet and put it back 24 volts.
MVPA #32564
WAC/B&G MVT
Patriot Guard Riders
NRA Life Member
NRA Certified Instructor
Rusty,
At the early stage of my M37 restoration, I was going to go with a 12 volt system. Along the way I bought an NOS distributor, Looks just like the 24 volt model we have, but the tag read 12 volt ignitor. Not5 sure what it was for, but it has the 12 volt coil you are talking about, so, they do exist for some unknown application. I ended up going with 24 volt so didnt end up using it.
Tim
Home 
