MTFCA Forum

Yup, this is a debate started by yours truly. All opinions and experiences offered should be considered.

After having my car almost burn to the ground due to a short in the electrical system, I proffer here that it's more advantageous to have an inline fuse located at the battery in your T than not. I'm shipping an in-line 20A in-line fuse to be installed with my voltage regulators I sell, but this applies to everyone, voltage regulator or not.

I submit the following picture of the burned up Model T wiring harness from MY Model T into evidence as exhibit A:
. Known and undeniable facts:

• ALL modern cars have multiple fuses to protect cars from electrical fires
  Shorts in any electrical system can cause fires. I can start a fire with a tiny 9v battery and have many times. Just ask my poor mother...
  Wires rubbing on metal eventually wear the insulation away.
  Mechanical Cutouts fail
  Diode Cutouts fail
  Voltage Regulators fail
  Model T generators can self destruct if there is no load attached
  A rebuilt generator costs about as much as your T when it was brand new, but is much less than an entire burned up car today

Now, with all those facts stated, I suggest installing a 20A fuse at the battery in ALL cars. Sure if it blows and your generator isn't adjusted properly, or even if it is, given long enough, there is a chance that the generator will burn up. But blowing a 20A fuse means something just shorted out in your electrical system. Why? Putting tin foil over the fuse might let you start the car, but why did it blow in the first place? A sure fire way to burn your car to the ground is to have a persistent short in your car's electrical system and not have a fuse to prevent that. See Exhibit A for details.

It's also recommended that you disconnect the battery when storing the car for long periods of time, like winter.
I know, you guys with magnetos AND batteries will have a unique and valid point of view.

But that's why debates were invented, so let the debate begin!
Again, all opinions are valuable. I've just stated mine.

Jeff

I agree, a fuse is essential. I recommend placing it at the starter switch on the 12 ga wire for those with starters. I had a fire too. I also keep a 1/2 inch open end wrench on a magnet inside the trunk on the quarter panel, always know where it is.

I'm in the process of installing a master disconnect switch under the front seat for the battery. Even before it gets to the starter switch. I put a fuse in the system at the starter switch power years ago and will continue. My question is; ....will there be any generator damage if the fuse blows?

Moxie26 wrote: ↑

Tue Sep 05, 2023 10:49 am

I'm in the process of installing a master disconnect switch under the front seat for the battery. Even before it gets to the starter switch. I put a fuse in the system at the starter switch power years ago and will continue. My question is; ....will there be any generator damage if the fuse blows?

Yes, maybe. If you accidentally shut off the master battery switch whall running, your generator is also @ risk.
If you monitor the ammeter you can possibly catch it in time & ground it out before it burns itself up.
I Have a grounding switch & idiot light on one T. If the light comes on, I can flip the switch to ground out the generator.
That same T is dizzy powered. If a fuse blew, The motor would stop running anyway. As would any T running on battery.
When running on mag, you are most vulnerable to a generator loss.

I dont have a fuse on any of my T's so far, but, maybe I will be persuaded.
Open minded but, not a hole in my head.

A fuse for prevention is worth a pound of cash! different Franklyn

Have also 'smoked' a wire on my Ts, twice! Once was the short ammeter to bat terminal yellow/black wire on the backside of the dash switch, it was fray I guess from age, but smoke poured from under the dash running down the road! Yikes.

Second time I had just installed an accessory dash lamp, the clip on type for 26-27 panel. Fed the wire between the dash and switch, thought there was gap, but no, shorted and found smoke in the garage coming from the '26 pickup! Bad by me, but saved by going back in the garage at luck time to find the smoking T, had there been a fuse, no scare, but that made me sure to add a fuse to all my T's and any friends that I do fix up on theirs too.


BTW, Ford originally put a FUSE in the first electric start systems installed in 1919, but then deleted it. Think that was short-sighted! (Pun intended)


For a safe Ford and a safe garage!

Thank you, Dan

Regarding the short wire on the back side of the switch, the last two harnesses I’ve gotten have had that jumper made from a smaller gauge wire than originally intended. If no fuse is installed, that is then the weak link in the charging circuit, which in my opinion isn’t ideal. I’ve been making a new jumper from 12 ga. wire.

Here's what my inline fuse looks like. 5 minute install. If your power for the car comes off of the starter foot switch, install it there instead.
I'm providing one with every Voltage Regulator I sell. Cheap insurance!

Thanks Jeff. !!!

Adding fail safe protection to your Model T electrical system is sound advice advocated by John Regan cira 2008 and still holds today. The recommended fuse value is 25A to protect a 20A system (12 AWG wire) or 1.25% rated operating current. Here is a link to the original post along with some related discussion. It's the first modification to my 1927 Touring. Thanks John! and thanks Jeff for reminding folks here.

http://www.mtfca.com/discus/messages/50 ... #POST98951

Ha! Even John Regan recommended it back in 2008...

"Some have argued that a fuse is a bad idea since if it blows - the generator may get toasted along with the lights but think about it - HOW COULD YOU POSSIBLY BE BETTER OFF if a fuse rated at 25 amps needed to blow because there was more than 25 amps through it!! NOPE - I vote strongly that you install a 25 amp fuse"

I couldn't have said it any better 15 years later!

Jeff

I put a 25 amp fuse at the starter switch to protect my car from a stray short, and from mistakes made by the nut between the steering wheel and the seat.

I have never used a fuse in any factory starter type T I've owned. I've also never had a problem. I have all my wiring made locally by a company that specializes in wiring looms for any car. They even weave the Ford tags into the harnesses! Use a fuse if you wish. I like my cars the way Ford built them.

Hmmm. I wonder if the owners and builders of the Hindenburg had any second thoughts?? I imagine safety features have been added to everything from house wiring to fuel delivery systems every decade for the past 12.

Well, the decade of the starter/generator Model T did provide for safe electric products, note this fuse for Ford.


And a fuse will prevent this:
(photo from a forum poster)


Here is my 'quick disconnect', fuse on the Yellow Bat wire.

Makes it easy to work on wiring or terminals at the switch or other places, removing the smoke making juice from the battery

Dan

I see your fuse is easy to access. So is mine. Why do so many people state you should put the fuse down by the starter switch? Does it really matter as long as a fuse in installed in the yellow wire? Thank you.

DHort wrote: ↑

Wed Sep 06, 2023 9:54 pm

Dan
I see your fuse is easy to access. So is mine. Why do so many people state you should put the fuse down by the starter switch? Does it really matter as long as a fuse in installed in the yellow wire? Thank you.

Some folks simply don't want to see it. This is why I recommend installing it on the starter switch or the battery - wherever power for the car is tapped. The fact is, the closer to the battery you can get it, the better you can prevent the next Hindenburg Disaster! wires leaving the point of origin will always be susceptible to wear and shorts next week or 100 years from now.

Jeff

DanTreace wrote: ↑

Wed Sep 06, 2023 4:44 pm

Well, the decade of the starter/generator Model T did provide for safe electric products, note this fuse for Ford.

THAT is super interesting. I always wondered when the glass fuse era started. They havent changed much and they are still in use in some applications even today.

Dan. I was looking for a photo I posted of my yellow fuse holder next to my starter when I found a 2012 post, posted by you with a similar picture. Here is an attachment you posted in 2012 along with the photo of the installed fuse next to the starter you have posted on this thread. It shows how to install fuses at the block. Jim Patrick