Paralell series switch nightmare

[thomastractorsvc]

12volt is the only way to go, make sure that the starter has the right number of teeth on it.

The previous owner of my B had the wrong starter gear drive to start out with and made a few bad spots on the starter ring. I cleaned it up and 85% of the time it catches, usually spins out when I have an audience. I will flip it over one day when I have to pull the transmission or it fails to catch.

[High Binder]

Beatngu, S/P switches are easy to hook up to batteries. You need to 12V batteries, doesn't matter where you locate them. I assume you have a negative ground system. Positive cable from battery #1 goes to starter. Negative cable from #1 goes to negative on S/P switch. Positive cable on battery #2 goes to positive on S/P switch. Negative cable on #2 goes to the starter.

[Maddog13407]

Mack was positive ground way into the early 70's. id still make sure it runs before you wasted time and money on batteries and cable. someone obviously unhooked the series parallel switch for a reason.

[rwood64083]

Lots of good info in this thread.

I assume these trucks will fire if pull started without batteries (?)

[Mike]

2 hours ago, rwood64083 said:

Lots of good info in this thread.

I assume these trucks will fire if pull started without batteries (?)

I hope so as long as Fire & Fuel are still available.

[beatngu]

Indeed there is. I recently bought 2 new truck batteries for it awaiting the big refire in a few weeks. Then I can start digging out the old wires and dink around with the charging system

[6368]

did you fix the series parallel system or take the easy way out?

[beatngu]

I fixed the switch, but if i had the money at the time it would have been a different story. I am trying to keep it original within reason.

[Underdog]

I converted my F over to 12v negative ground and eliminated the S/P switch(it had a broken stud anyway). It cranked the 24v starter OK with 2 group 31 batteries, but when I upgraded the engine I also put in a 12v starter. Simple and reliable.

[beatngu]

No joke that is exactly what I have sitting in my kitchen right now, a pair of group 31s. I had car batteries on it before but when it got cold out they wouldnt budge the starter

[Hobert62]

6 minutes ago, Underdog said:

I converted my F over to 12v negative ground and eliminated the S/P switch(it had a broken stud anyway). It cranked the 24v starter OK with 2 group 31 batteries, but when I upgraded the engine I also put in a 12v starter. Simple and reliable.

After I bought the 12 volt starter for mine a local garage owner told me my 24 volt probably would have been fine.   He was working on a local farm truck one time that was negative ground 12volt and it had a 24 volt starter on it for nobody new how long.     

[41chevy]

1 hour ago, Hobert62 said:

After I bought the 12 volt starter for mine a local garage owner told me my 24 volt probably would have been fine.   He was working on a local farm truck one time that was negative ground 12volt and it had a 24 volt starter on it for nobody new how long.     

  Using a 12 volt or 24 volt starter they will both perform identically, but the 12V motor would draw twice as much current from its 12V supply compared to the 24V motor on a 24V supply. Same as a 6 volt starter has a higher draw than a 12 volt unit.