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Location for a cutoff switch and starter draw

Posted: Fri Oct 03, 2025 9:50 pm
by Dennis_Brown
The 23 coupe I recently acquired had a cut off switch under the driver's seat that had failed from a load when the plastic base melted, it is also going to be a pain having to lift the seat or reach into the trunk to get to it to operate it .
I have a good quality switch to replace it but was thinking about putting it behind the left splash apron on a bracket attached to the frame. I may have to get on a knee to reach under to get to it, but it would be high enough to be in a fairly dry area.
Any comments appreciated.
I am also putting a 6 volt starter solenoid on it using the foot switch to trip it. Reworking some battery cables as the starter does not turn the engine over very fast. I put a woven strap from the frame to the hogshead and no change.
One question I have on cables and draw. The cable from the battery to the solenoid appears to be a 1-0 size. The cable from the switch to the starter is just over 2 feet long and smaller than 1-0 in size.. could my starter problem be located there. The ground cables are 1-0 in size.

Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 7:09 am
by Humblej
The original 6v Ford starting system works great when everything is in specs. My advice is to yank out all that new stuff and return to original...no cut off switch, no solenoid, no local auto parts battery cables. If your 100 year old starter still turns slow like a tractor with a dead battery your starter needs a rebuild, if your starter has never been rebuilt it needs a rebuild, if your starter was repaired by a previous owner it needs a rebuild, and by rebuild I mean buy one from a reputable model T starter/generator rebuilder.

Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 9:20 am
by TXGOAT2
The ENTIRE starter motor circuit must consist of quality, heavy gauge material, and all ground points must be clean and tight. Any weak link will degrade performance of the entire system. That's true whether the system is original Ford or an improved system.

A cheap or undersized battery is no bargain,, and neither are cheap or undersized cables, switches, et cetera.

Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 9:36 am
by DanTreace
For 6v starting, the battery to switch and switch to starter cables must be OO gauge or known too as 2/O gauge , they are appx 3/4 inch thick. Don’t use premade 12 volt cables you will have problems starting. The ground cable preferably should be a woven strap.

Have tested or new battery, have all cable contact points cleaned to bare metal, esp. all grounds.

Remove the cut-off, it’s just a trouble maker. A solenoid is optional, mounted satisfactorily , (use OO cables ) and frame grounded.

For best safety, add a fuse to the yellow wire from the switch 6v hot terminal, mounted in line near the switch, but mounted in line near the terminal block is easy access, for disconnecting 6v hot to the chassis when working on dash, lamps, or other 6v items on the T. The fuse will save the T from rare but can happen shorts to the wiring, which will smoke wires and start fires.



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Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 10:01 am
by Craig Leach
Hi Dennis,
I put mine on the ground cable @ the frame. Use a good switch like a Cole Hersey that has a positive detent. Yes hard to get to but shuts of
everything.
Craig.

Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 10:21 am
by TXGOAT2
Starter draw should be 200 amps or less. Electric starters typically have a duty cycle of 10 to 15 seconds. Don't grind the starter for more than 10 seconds. Less is better. If the engine won't start in under 10 seconds of cranking, stop cranking and find out why. The starter should rest for a minute or two between consecutive starting attempts. A well charged battery of adequate size is essential to good starter performance and long starter life.

Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 5:22 pm
by JohnH
starter_current.jpg
starter_current.jpg (60.17 KiB) Viewed 121 times

Re: Location for a cutoff switch and starter draw

Posted: Sat Oct 04, 2025 6:07 pm
by TXGOAT2
Not clear what the test consisted of.