Using Coil Box Posts as a Junction Box

[ryanf1023]

My T is being built as a black era car, although I'm not super strict on any particular year or wiring configuration. I have the coil box with the front mounted switch, with the separate posts on the rear for each of battery and magneto.

My thought is to use these posts as a junction box for all electrical units on my car, although the magneto and battery systems will be entirely isolated from each other. For example, the leads for both my magneto horn and magneto lights will come off the magneto post on the coil box, being served from the magneto pickup. The leads for my battery lights, brake lights, spotlight, and battery horn will come off of the battery post on the coil box, being served from my battery. The coil box will function as usual with the BAT - OFF - MAG positions. All units of course will have their own switches.

I'm not seeing any issues with this, although my ears are open for more experienced T-ers to chime in. My thoughts are, my magneto system and battery system are entirely isolated; there is no risk of running current to my magneto.

There are a few reasons why I want to do this. One, it's a fairly simple setup. I've had frustrations with my Model A wiring using a funny splice of the original system and a Pentronix distributor that I inherited (the electrical system, not the car), which is not very easy to work on. Second, much like some are stimulated and excited by eeking out as much power as possible in these little Model Ts through special heads, cranks, etcetera, I love the fascination with early automotive electrical systems and have a desire to experiment and try something like this. Third, it leaves the option open to add or take away any other electrical system on the car with incredible ease, and not really having to touch anything else.

FWIW, my car will begin its life as a non-starter and non-generator car.

Has anyone tried something like this?

[RVA23T]

You can mount a terminal block on the inside of the cab under the dash using the existing mounting holes in the metal firewall. I have my extra lighting wired off a 2nd terminal block inside/under my dash, it just required 2 longer screws. I can post a picture tomorrow afternoon if it will help.

[ryanf1023]

That’s an option too. Thanks for sharing. I would be interested in seeing a photo.

[Humblej]

Ford used a junction block on the firewall from about 1919 to the end of production. It makes the wiring clean and organized. The block is located above the steering column on the engine side of the firewall.

[TWrenn]

Ford used a junction block on the firewall from about 1919 to the end of production. It makes the wiring clean and organized. The block is located above the steering column on the engine side of the firewall.
20230305_113621[6604].jpg

Just do it this way as Jeff shows. It's not rocket science either and as he says keeps things organized.

[ryanf1023]

Thank you all for the replies.

[Norman Kling]

Seems to be very strange the way you want to do things. The coil box on most of the black cars didn't have a switch mounted on it but the switch was on a dash panel with an ammeter for the battery system. The original switch had connections for battery and for magneto and the switch turned either way so they did not get connected together if wired correctly. The engine was made to run on coils. Usually a distributor was placed because the magneto didn't work. Why not use the original wiring loom with 6 volt electric lights and a 6 volt generator with 6 volt starter. When you get old you will thank yourself that you have a starter and not have to crank. Of course, you can crank with a starter if you want to experience cranking. You need to decide what year you want and what body, because some parts are different from year to year. Then if you want to add such items as turn signals etc you can also get 6 volt versions of them. Anyway, a Model T is a Model T. Some modifications make it into a model M The M stands for monstrosity
Norm

[RajoRacer]

Norm - non starter cars had the switch on the coilbox.

[Oldav8tor]

My 1917 has a coil box mounted switch. I'm running 12 volts and I do have a lead from the terminal strip (+) feed to the coil box battery post. I also have a tap off that post to my light switch.

You mention magneto bulbs..... that's what my 17 originally had and they gave me all sorts of problems. Obviously the brightness varied with engine rpm and it was possible to "blow" them. Since they were wired in series, lose one, you lose them both. If you have a decent battery, it might be time to re-wire the lights in parallel and install LED's.

Also, since my '17 lacks a generator I use a Regan "Hot Shot" to charge the battery from the magneto. It has worked well for me.

[TRDxB2]

My T is being built as a black era car, although I'm not super strict on any particular year or wiring configuration. I have the coil box with the front mounted switch, with the separate posts on the rear for each of battery and magneto.

My thought is to use these posts as a junction box for all electrical units on my car, although the magneto and battery systems will be entirely isolated from each other. For example, the leads for both my magneto horn and magneto lights will come off the magneto post on the coil box, being served from the magneto pickup. The leads for my battery lights, brake lights, spotlight, and battery horn will come off of the battery post on the coil box, being served from my battery. The coil box will function as usual with the BAT - OFF - MAG positions. All units of course will have their own switches.

I'm not seeing any issues with this, although my ears are open for more experienced T-ers to chime in. My thoughts are, my magneto system and battery system are entirely isolated; there is no risk of running current to my magneto.

There are a few reasons why I want to do this. One, it's a fairly simple setup. I've had frustrations with my Model A wiring using a funny splice of the original system and a Pentronix distributor that I inherited (the electrical system, not the car), which is not very easy to work on. Second, much like some are stimulated and excited by eeking out as much power as possible in these little Model Ts through special heads, cranks, etcetera, I love the fascination with early automotive electrical systems and have a desire to experiment and try something like this. Third, it leaves the option open to add or take away any other electrical system on the car with incredible ease, and not really having to touch anything else.

FWIW, my car will begin its life as a non-starter and non-generator car.

Has anyone tried something like this?

I created a wiring diagram as a starter as you described and how it could be updated later. Input from others welcome
Best to get the wiring harnesses for the later diagram.
diagram shows the optional horn wiring
Just because there is a post on the back of the box for BAT doesn't mean its wired up.

[ryanf1023]

I appreciate you drawing that out. It looks like I don’t have to modify it as much as I first thought.

[TRDxB2]

I appreciate you drawing that out. It looks like I don’t have to modify it as much as I first thought.

Keeping the wiring pr the diagram will take a lot of guess work out of any future changes by you or anyone else. The terminal block eliminates splices and uses standard harnesses. Lots of pros & cons on 12 volt setups. How do you intend to charge your battery via MAG kit or smart trickle charger? These 6v-12v headlight bulbs are now the rage. No need for good reflectors

[aDave]

Frank,
Have you a vendor's name and number for that bulb, please?
Dave

[TRDxB2]

Frank,
Have you a vendor's name and number for that bulb, please?
Dave

They are sold by most supplier's now. $$ vary. They are not cheep but can be justified if need a reflector
6V, 8V, 12V
Positive or Negative Ground (chassis) electrical systems with no wiring changes
Generator or Alternator
Color is ~6500K (Bright White)
Low beams draw 0.8A typ @ 6.3V (versus 3.6A typ for 1110/13007D type incandescent bulb)
High beams draw 1.4A typ @ 6.3V (versus 4.5A typ for 1110/13007D type incandescent bulb)
https://www.modeltford.com/item/6572LED.aspx
https://www.snydersantiqueauto.com/prod ... &cat=41889
https://www.mikes-afordable.com/product ... EDFOC.html

[RVA23T]

Here is my 2nd terminal block, forgot I had 30amp fuse in it, need to change that. Ran a line off the battery to the fuse and then split it 3x for the acessories. I'm still using 6v.

[aDave]

Thank you veery much Frank!

Boy, prices certainly are VARIABLE !

Dave

[RVA23T]

Thank you veery much Frank!

Boy, prices certainly are VARIABLE !

Dave

There is alot of 6v Led options here as well:

www.ledlight.com/6-volt-negative-ground ... spx?Page=1

[Allan]

Finally, an LED bulb with its own reflector!

Allan from down under.