Fuse blowing

[ezloader]

Hi
Hooked up new wiring,lights and horn worked
properly,fired the old girl up ran for 10 minutes while I checked exhaust leaks etc.suddenly shut off thought maybe no fuel nope lots of fuel.
Noticed the fuse blown,replaced fuse and as soon as I switched the battery on fuse blew.can’t see any issues re shorts etc.
Any ideas? Maybe generator cut out or?
Thanks
DJ

[Tom Endy]

This may help. Also check the terminal block on the firewall. The repose often allows the head of each screw to back off at the back and touch the firewall and short out.

http://www.santaanitaas.org/wp-conte...Quick-easy.pdf

Tom Endy

[ezloader]

Good info Tom I’ll check things out for sure,
Thanks
Daryl

[nkaminar]

There are several possible sources of shorts. The junction box as Tom said but also the sockets for the headlights. Methodically go through the wiring to find the short. Disconnect everything and remove the light switch. Use your ohm meter to check for shorts to ground on all the wiring until you find the short. Then investigate what is causing the short in that circuit.

If it is a socket in the headlights you can extend the wiring into the insides of the buckets and make a connection there using individual pin and socket connections for each wire. Or fix the short in the original socket.

[ezloader]

No luck yet thanks for the info can’t figure out
Why it ran perfect for 10 min then popped the fuse
Thought maybe generator heated up and shorted..
We’ll see

[Kurt in NJ]

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Separate the lights from the rest of the system by unhooking the wire to them at the generator and see if the problem is in the lights

[nkaminar]

Here is something that may help: https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

[rotorwrench]

The lights won't affect the fuse if they are off. The dash light can be an exception depending on type. The wire can rub up against the fuel tank in some situations. The brake light is another one that can have shorts.

[Rob Doe]

EZ, I have read Mr. Endy's article about finding faults in the electrical circuits. His instructions are straight forward and will quickly isolate the fault to a particular circuit.

I'm no expert on Model A electrical, assuming wired stock Model A wiring:

An unintended ground (some call it a short) between the + post of the coil, to and through the switch, to and through the heavy cable, and up through the distributor to the points will not blow the safety fuse on the starter switch. Such grounds are after the load (the primary coil winding). They might ruin the coil, but won't blow the fuse. A steady, not intermittent ground in that area should show on the ammeter if the car has the November 1929 wiring change from page 390 of the service bulletins?

As I recall, removing and separating the 3 wires at the generator, alternator and installing a new fuse will validate all the wires back up through the terminal box and back to the battery post fuse. Luck to ya.

[ezloader]

Thanks everyone for the help and ideas,Did all th checks all look good,I bypassed the generator lights and horn working as they should no blown fuse.cut out has continuity so must be in the generator itself.
That make sense?
DJ

[nkaminar]

Sounds like the cutout is bad. Is it the old mechanical type or an electronic type?

[ezloader]

Took the genny off my other car which I hate to do, but phaeton runs well and no blowing fuses..it’s the old style cutout which had continuity until I dropped the darn thing.

Getting old is no place for sissies.

[Badpuppy]

Cutout contacts are open until the gen spins up enough to exceed battery voltage. A bad one will show continuity between terminals.

[ezloader]

Ok thanks I’ll try another cutout
Good info
Thanks

[Badpuppy]

https://fordbarn.com/forum/showthrea...7696&showall=1

Tom Wesenberg (RIP) explains how these old cutouts can be refurbished in this thread.

[LuisUp]

Originally Posted by ezloader

Hi
Hooked up new wiring,lights and horn worked
properly,fired the old girl up ran for 10 minutes while I checked exhaust leaks etc.suddenly shut off thought maybe no fuel nope lots of fuel.
Noticed the fuse blown,replaced fuse and as soon as I switched the battery on fuse blew.can’t see any issues re shorts etc.
Any ideas? Maybe generator cut out or?
Thanks
DJ

After hooking up new wiring, your vehicle suddenly shut off and blew a fuse, which keeps happening even after replacement; you're seeking help to identify the issue, such as a possible generator cut-out or other problems.

[Diastole]

Fuse vs Circuit Breaker

As I read this thread about all the fuses that blow, what is the prevailing theory on using an automotive DC 30 amp current breaker?

Pulling fuses every night has been cautioned to weaken the clasps holding the fuse in place. Exposed terminals are easy locations to inadvertently short a wrench. And, a breaker with a manual trip could serve as a cut-off switch.

Grainger's Automotive-Circuit-Breaker-30PD07
or Amazon's RedWolf 30amp DC Circuit Breaker

Traditionalists would favor fuses, but Henry did not see fit to install one. So tradition portends no electrical protection and the modern breaker is similar to the modern fuse block of the 1950's.

Also, why not isolate the starter. I recognize that a starter short is exceedingly unlikely and it can pull a heavy initial amp load so a fuse fuse/breaker would trip every start, but if you are going to isolate the electrical for safety, then isolate. Some posters advocate a two fuse setup, i am not sure of the wiring schematic for this arrangement though.

Bottom line, to a new Model A'er, (as I have read all the threads) is ....
1) Protect the vehicle from the numerous possible shorts
2) Install an electrical cutoff switch for safety and security
3) Possibly use two safety devices, one at starter and one at alternator/generator

A) Tie a zip tie to fuse to make it less hard to remove
B) Do not remove fuse too often to weaken prongs
C) Carry extra fuses
D) Do not accidently touch exposed prongs with a wrench
E) If you are going to use a .22 gun cartridge, make sure it has been fired first

It seems to me a breaker like I attached from some of the others that have posted seems to check all the boxes and avoid all the pitfalls.

Why not use a waterproof automotive DC 30 amp breaker instead of a fuse?


Diastole

[PC/SR]

[The lights won't affect the fuse if they are off. The dash light can be an exception depending on type. The wire can rub up against the fuel tank in some situations. The brake light is another one that can have shorts.]


True the lights will not affect the fuse if they are off, but a short in the switch can occur with the lights off. I spent a few hours on a friends car trying to find a short, which did not occur when the lights were disconnected at the generator. Eventually found it in the back of the rotating switch plate. Disconnect the lights and see what happens.

[rotorwrench]

The original cloth covered wire only had a form of resin to hold the cloth insulation. The more modern cloth covered reproduction wire has wire that uses modern insulation prior to the braided cloth installation. There can also be problems with the spade connectors that attach to the switch plate terminals. Some don't fit together well and can come loose. If the modern type reproduction wiring is well made and the use of bitumin covered loom is generous enough then problems with the electrical system are less common. If the wiring is very old and brittle then it's just a matter of time before a problem will occur.

Bad ground paths can also generate excess heat so take good care of all ground connections.

[Wick]

Did you also replace the wiring behind the dash?