Question about fuses

[29Cabriolet]

I am replacing much of the wiring from the battery through the terminal box and out to the instrument panel/distributor/coil, etc. The installation diagram for one of the harnesses having two wires, Yellow/Black and Yellow (Part no A14406 - Cut out to terminal wire) is as follows: Yellow/Black: Generator cut out to Terminal box; and Yellow: starting switch to terminal box.

I have a single fuse on the fire wall wired between the starting switch and the terminal box. Since Les Andrews makes no mention of any fuses anywhere in his handbook, I can only conclude fuses were not part of Henry's original design.

Further, I would assume that most if not all restorers include fuse protection "add on" or "upgrade" for all the reasons fuses are used. Interested in any comments on this.

Thanks

 

[Patrick L.]

Your right about Ford not installing any fuses. Many folks do add a fuse, many don't.

 

[Kurt in NJ]

A fuse failure in the wiring between the battery and generator can cause the generator to burn up --and any light bulbs that are on t0 burn out

I feel a better place for a fuse is at the generator for the light system feed, and if you have a dome light a low amperage fuse to protect the wiring going through the very easy to burn upholstry (cotton wadding doesn't take much of a spark to burn)

When choosing fuses you have to decide if you are fusing to protect the wire, or the componets--and to protect wiring it has to be sized to protect the smallest gauge wire in the circuit

When there is a fuse connection failure in the commonly used "fuse at the starter" the generator gets disconnected from the battery, the car can continue to run, the charging voltage can get over 40 volts --this will test any weak insulation, soon the generator overheats and smoke is let out of wires.

I am a no fuse person at this time, the first time driving the newly restored car had a fuse holder failure that caused smoking generator, burnd out bulbs,stuck dead in the road, towed home, got rid of the fuse holder ---no more generator problems in the last 40 years, always drive home.

 

[Barry B./ Ma.]

I had the same problem with the starter mounted fuse Kurt as the clip started to fracture and the circuit opened. I removed the fuse and holder and put an in line 20 amp from the generator in the light and horn circuit. What prompted that was a short in the light circuit and the fuse on the starter location made it almost impossible to find the short location as that fuse blew repeatedly causing burned out bulbs even in the tailights. The fuse in the light horn circuit narrows down the troubleshoot area and doesn't affect the ignition.

 

[steve s]

If the common starter-mounted fuse fails AND you're running an alternator,

1. will the alternator keep the ignition running so you don't have to worry about the motor dying, and

2. will the alternator's voltage regulator keep it from burning up?

 

[SkipShift]

I have a short somewhere with the headlights that I'm working on. My fuse is on top of the starter. The fuse blows when I turn on the headlight brights and the motor dies. I'll repost when I find the problem. I've been thinking about replacing the starter mount fuse holder with a water proof blade type.

 

[Tom Wesenberg]

If the common starter-mounted fuse fails AND you're running an alternator,

1. will the alternator keep the ignition running so you don't have to worry about the motor dying, and

2. will the alternator's voltage regulator keep it from burning up?

I haven't tried it, but I believe the answer is yes to both questions.

Though it isn't recommended to run an alternator disconnected from the battery, I've seen it done many times in the junk yard.

 

[Tom Wesenberg]

I have a short somewhere with the headlights that I'm working on. My fuse is on top of the starter. The fuse blows when I turn on the headlight brights and the motor dies. I'll repost when I find the problem. I've been thinking about replacing the starter mount fuse holder with a water proof blade type.

I clip a light or buzzer in place of the fuse, then when you find the short the light goes out or the buzzer stops. Many light shorts are found in repro headlamp socket terminals, where the contacts are a bit too large and touch ground, or in the repro brake switch.

 

[CarlG]

... I've been thinking about replacing the starter mount fuse holder with a water proof blade type.

This isn't "waterproof", but it does have a cover and works quite well. I mounted this to the firewall with Velcro, therefore no holes.

 

[mngreen]

I haven't tried it, but I believe the answer is yes to both questions.

Though it isn't recommended to run an alternator disconnected from the battery, I've seen it done many times in the junk yard.

Here's a follow-on question:

With the fuse on the starter with an alternator/VR setup, will the fuse even blow on a dead short (let's say on the brake light at the rear of the vehicle) when the vehicle is running?

 

[BILL WILLIAMSON]

29Cabriolet,
I run a 30 Amp G.M. blade type circuit breaker, with the provided pig tail holder on the main power lead at the starter. On the power leads to the horn & headligts, close to the HOT terminal on the cut out, I run a 20 Amp breaker, on each one.
My thought is that IF you have a SHORT, one of the 20 Amp breakers will open BEFORE the 30 Amp one will, & WON'T screw up the charging system & burn up the generator, & ignition system, and the car will keep running.
The breakers are 12 volt, BUT will work O.K, on 6 Volt, as they depend on AMPERAGE to open, NOT VOLTAGE!
Vermin is ALL stock & is on 6 Volt.----Bill W.

 

[Tom Wesenberg]

Here's a follow-on question:

With the fuse on the starter with an alternator/VR setup, will the fuse even blow on a dead short (let's say on the brake light at the rear of the vehicle) when the vehicle is running?

Yes, it should still blow.
Kurt explained it well and I also don't use a fuse, but if I did, I'd connect it between the cutout and lights/horn terminal. This would fuse all the lights and horn, which is where most people have problems with shorts.

 

[rons49]

IMO, if the fuse blows while driving above the "cut in speed" the generator is powering the car. Indeed the voltage will be unregulated, and depending on the RPMs voltage will rise. OK, that will cause bulbs to POP. but a fire will be avoided from wires catching fire . Bulbs are cheap. That is if the cut in speed (engine rpm) stays above idle. At idle the engine will shut down and not restart. Usually idle ( or when parked) is when a fire starts from a short , other then when turning on lights or pressing the horn. I glance at the amp gauge often. Also a fused car will not burn when put away, if an issue arises , let's say in the garage. The only thing not protected by the "starter mounted" fuse is the starter motor... and the kill switch takes care of that.

 

[Tom Wesenberg]

That's another advantage of using an electronic voltage regulator in the generator. Even if I remove my battery cable with the engine running at high RPM the output voltage is regulated to a safe maximum and won't blow lights or burn itself up.

 

[CarlG]

Do the lights/horn wires have to be connected to the cutout (albeit thru a fuse if desired) or can they be connected to "any" hot lead (such as directly to the battery)?

 

[Tom Wesenberg]

Do the lights/horn wires have to be connected to the cutout (albeit thru a fuse if desired) or can they be connected to "any" hot lead (such as directly to the battery)?

If you want them to read through the ammeter then they should remain connect at the cutout as original. Otherwise any hot connection will work if you want to run extra wire.

 

[Willie Krash]

In the for what's it worth dept we took a self exciting Delco 10si alt out of the box and ran it at 14v and took it to open circuit. It went to 29V it secondary regulation point as expected.

We use stator fired VRs with no diode trio and I don't know if they would go to secondary or just shut down. Most are NOT stator fired, it is our preference and is more costly. That is to say they are atypical.