03-25-2024, 06:37 PM | #1 |
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Fuse blowing
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 |
03-25-2024, 07:10 PM | #2 |
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Re: Fuse blowing
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 |
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03-25-2024, 08:04 PM | #3 |
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Re: Fuse blowing
Good info Tom I’ll check things out for sure,
Thanks Daryl |
03-26-2024, 05:54 AM | #4 |
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Re: Fuse blowing
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.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
03-26-2024, 07:42 AM | #5 |
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Re: Fuse blowing
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 |
03-26-2024, 09:09 AM | #6 |
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Re: Fuse blowing
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03-26-2024, 10:43 AM | #7 |
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Re: Fuse blowing
Here is something that may help: https://www.mafca.com/downloads/Semi...ex%20Janke.pdf
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
03-26-2024, 11:30 AM | #8 |
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Re: Fuse blowing
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.
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03-26-2024, 01:38 PM | #9 |
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Re: Fuse blowing
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.
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"It ain't what you know for certain that gets ya in trouble. It's what ya know for certain that just ain't so!" Last edited by Rob Doe; 03-26-2024 at 01:43 PM. |
03-26-2024, 08:48 PM | #10 |
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Re: Fuse blowing
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 |
03-27-2024, 08:59 AM | #11 |
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Re: Fuse blowing
Sounds like the cutout is bad. Is it the old mechanical type or an electronic type?
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
03-28-2024, 07:21 AM | #12 |
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Re: Fuse blowing
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.
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03-28-2024, 09:14 AM | #13 |
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Re: Fuse blowing
Cutout contacts are open until the gen spins up enough to exceed battery voltage. A bad one will show continuity between terminals.
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03-28-2024, 08:22 PM | #14 |
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Re: Fuse blowing
Ok thanks I’ll try another cutout
Good info Thanks |
03-29-2024, 08:41 AM | #15 |
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Re: Fuse blowing
https://fordbarn.com/forum/showthrea...7696&showall=1
Tom Wesenberg (RIP) explains how these old cutouts can be refurbished in this thread. |
03-29-2024, 09:07 AM | #16 | |
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Re: Fuse blowing
Quote:
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03-29-2024, 09:28 AM | #17 |
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Re: Fuse blowing
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 |
03-29-2024, 09:59 AM | #18 |
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Re: Fuse blowing
[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. |
03-29-2024, 02:04 PM | #19 |
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Re: Fuse blowing
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. |
03-31-2024, 03:19 PM | #20 |
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Re: Fuse blowing
Did you also replace the wiring behind the dash?
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04-17-2024, 08:08 AM | #21 |
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Re: Fuse blowing
When i first got my Model A a year and a half ago, I was going nuts with "blown" fuses. Probably a dozen of them. Discovered that the fuses were junk. Two different batches of them. With the fuse holder mounted on the starter, the fuse would get hot enough that the metal end cap would detach from the fusable element and open the circuit. Fuse would visually look fine but have no continuity. In most cases, the metal cap would fall right off the glass. I ultimately mounted a 30A breaker under the dash eliminating the ugly fuse holder and restoring the under-hood wiring to factory appearance. The breaker has never popped once.
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04-17-2024, 09:02 AM | #22 |
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Re: Fuse blowing
There are different types of breakers:
1. The type 1 which must be manually reset after it trips. 2. The type 2 which resets by its self automatically after it cools down. Type # 1 is much safer and less likely to start a fire. With type #2 if a short happens when nobody is around (at night or when buying ice cream) the breaker will reset itself repeatedly as long as short remains. Finally breaker will overheat and fail. 1. If you are lucky it will fail as an open circuit and there will be no fire. 2. Breaker can also fail in a shorted condition which may start a fire. The IBM machines (punch card machines through System 3090 main frame) that I worked on for 30 years ALL had the manual reset breakers or fuses to prevent a fire from being started. I never saw an auto-reset breaker ... never. Fire is the reason why they were never used. Many of the older punch card machines had hundreds of manual reset breakers or fuses. Last edited by Benson; 04-17-2024 at 09:26 AM. |
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04-17-2024, 01:15 PM | #23 |
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Re: Fuse blowing
Ford used auto reset circuit breakers from the 30s clear up into the 50s. Early cars burned up mostly due to no circuit protection at all. Fuses will do the job but a person should carry a spare and find the problem before inserting a new fuse. Short Stop breakers were used in trucks clear up into the modern era due to all the lighting they had to have. I've seen them wear out over time but I've never seen a short circuit happen when a car is setting with everything off. If someone turns on a load and it trips the breaker then it's apparent that there is a short in that circuit. Find the short and repair it before turning the load on again.
A 16 gauge wire needs a lower amp rated fuse. Standard practices calls out a 10-amp fuse. A 15 or a 20 amp fuse would be better than a 30. A 15 amp circuit breaker is acceptable for a 16-gauge wire. Last edited by rotorwrench; 04-17-2024 at 01:24 PM. |
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