Technical 1950 Ford f1 30 amp fuse keeps blowing

Hello all,

I have a 1950 Ford f1 that was converted to a 12 volt system and uses an 8 circuit kwik wiring harness. A couple weeks ago, dash and gauges would get power with key on but wouldn’t start. Took out starter, had it tested, it was bad, got a new one, installed, started truck, it was fine. Couple days later went to start, nothing, no power at gauges. Replaced ground wires from battery to frame, engine to frame and frame to cab. Nothing, no start, no power to gauges. Checked fuses and 30 amp fuse for “gauges” (according to kwik website) was blown. Replaced 30 amp fuse, truck started. Wired up a tack to key switch to calibrate idle speed on new carb, noticed either my alternator or power steering pump belt was whining. Removed alternator belt to see if it was that one, ran off battery for a little till battery died and determined it was alternator belt. Reinstalled and tightened alternator belt, went to start truck and same issue, 30 amp gauges fuse was blown again.

Thoughts on what keeps blowing that fuse? Bad, new, alternator? Bad ignition switch? Wire issue, how to test it?

 

Do you have the alternator wired to the ammeter gauge (or gen light) through the fuse? With most wiring kits I've seen, the gauge fuse is just for the gauges and is usually about 10 amps. Go back and look at the wiring schematic that came with the kit.

 

The alternator appears to be wired from the fuse box/wiring harness bundle of cables (it’s hard to trace exactly where it goes but it doesn’t go to starter or battery). And there is also a gauge on my dash for the alternator. Does that answer your question?

 

Also backstory: everything was fine for years before I couldn’t start it one day, replaced the starter and started my journey of electrical fun…

additional information: alternator and starter are both receiving voltage from battery when 30amp fuse is blown but key ignition switch and gauges are not receiving voltage.

 

is this an ammeter or a volt meter? How about a picture, or a description of the numbers? ammeters have a range like -60 0 +60 while a volt meter will have a range like 8 to 18

 

Sorry, miss understood the question. Correct it is voltage and I have been using a multimeter but only checking voltage at wires and terminals. Here is a photo of the gauges when it has power (key to on and fuse replaced). I’ll test and see if I can tell which step blows the fuse (key on or ignition turn or running)

 

My guess is that the thing is just not wired correctly.

I would expect the GAUGE fuse to provide power that comes from the IGN circuit on the ignition switch, to the gauges. It should not be providing power to the ignition switch!

 

If the truck wouldn't start with that fuse blown, there is more than the gauges being powered by that 30 amp fuse.

 

Yeah I’ll have to track down what all is powered by that fuse. I replaced it and it started up and ran for about 2 minutes before it died and now won’t start. Gauges have power and that 30amp fuse hasn’t blown but when I turn the key, nothing. No crank from the starter. Hooked up a trickle charger and battery is fully charged.

 

When trouble shooting an electrical problem, we like to go to the simplest possibilities and then rule out those first. It sure sounds like there is something that has loosened and makes at times. Then it doesn't. You changed the starter and possibly cause some wiring to loose its connection? When it is intermittent and not constant, that is where I would look first.

 

Ok I checked the wires at the starter and they look good but I did notice a fusible link on the S terminal that leads to my ignition. I wonder if that’s one of the issues with the intermediate starting and blowing fuses? If I replace the fusible link, what gauge wire should I use?

 

When you replaced the starter and then cables, did you clean all the connection points? Just putting a new ground cable on won't help if it's attached to a rusty frame. Sand all corrosion off these points, then use dielectric grease on the terminals and studs to keep them from corroding again.

 

30A is too big for a gauge circuit. Such an amperage fuse would require a 10 AWG (minimum) wire behind it; anything smaller won't be properly protected by the fuse.

Fusible links are generally sized to be 2 wire gauges smaller than the wire they're protecting. For example a 12 AWG wire would use a 16 AWG fusible link.

I suspect something isn't wired properly.

 

So I removed the tachometer I had wired up to see and adjust my idle mixture and speed screws with my new carburetor. Then I replaced the positive cable from the battery to my starter. It was going about 3ft to the cab for a kill switch then back to the starter. I wasn’t sure if that was shorting under load or just not provide enough power so I just bypassed it and got a new cable and ran it from battery to alternator. I also tightened up the alternator belt so it runs constant now, was slipping before and not provide constant voltage.

started up and no blown fuse. Yet… I plan to start it a couple times a day and turn on and off lights and stuff and see if anything trips anything.

maybe it was the kill switch and old battery cables shorting and blowing the fuse or alternator fluctuating with slipping pulley?

 

It’s still not wired properly….

 

I agree. I plan to trace all the wires and see what’s connected to what.

So far I’ve traced:
-Hot from battery to starter.
-R on starter to dash then i don’t know. it should go to my distributor? But I’m guessing not directly from starter due to voltage/amps? so it probably goes through a breaker? Distributor does get voltage with key on.
-S on starter to neutral safet switch then dash then I don’t know. Likely back of ignition switch?
-large gauge, maybe 8-10, to dash then I don’t know. I’m thinking that’s the main power line for all dash and accessories?

alternator has power all the time, even with key in off, that seem correct?

 

The large wire should be the main power feed. It should go to the B terminal on the ignition switch.

The R wire should go to from the starter to the positive side of the ignition coil. It might go to the coil side of the ballast resistor.

The S wire should go through the neutral safety switch, then to the S terminal on the ignition switch.

The volt meter should not get power unless the key is on. It should get power from the Gagues fuse. The other gauges should also get power from this fuse. But nothing else should.

If it were mine, I'd disconnect the battery, and take stuff apart far enough that I could trace each wire. And then make a schematic drawing of it.

 

Great thank you. Yeah I’ll try to start testing continuity and make a map.

 

Got a link to a schematic for the wiring kit?

 

https://kwikwire.com/collections/wiring-schematics

https://studylib.net/doc/18599971/kwik-wire-instruction-manual

 

Cool I’ll have to check out that schematic. I know it’s an 8 circuit kwik wire. Here is the link to the product.

https://kwikwire.com/products/8-circuit-budget-wire-harness

I found a general instruction manual on there website I was referencing. My great uncle built the truck about 10 years ago and doesn’t remember exactly the wire colors he used for stuff. It’s a Ford truck with a Chevy engine so I’ve been mainly looking at all the GM diagrams but i don’t know if he kept to the GM colors. The writing is so small on the wires I have a hard time reading them but I’ll see if they match what they are actually connected to.

 

It’s possible the fuse was replaced with a larger one than what it should have been. As said before, 30amp is way too big for gauge fuses. This may have happened because someone spliced in and added something, started blowing the original fuse, so put in a larger one.
Not a good thing
I’d start by looking for splices in the harness, should be easy to spot.
An 8 circuit harness is pretty basic, right? So what has been added, stereo, etc, that may come on when key is in run position, that an old vehicle would not have had?

 

Fuses only blow because there is too much of a load or a short on the load side of the fuse.
Short= Bare wire making contact with metal that is grounded or possibly a defective unit that is in the circuit.
The load in the circuit is too high for the fuse. Example a 10 amp radio fuse blowing because there is an Amp that draws 50 amps wired into the wire to the radio rather than being run to the fuse box and fused by a proper size fuse or breaker.
The power coming out of a battery or alternator will not blow a fuse no matter how much power it puts out. The problem is always on the load side of the fuse not the power side.

 

I agree, 30amps is way to big for the wire sizes. I’m thinking there is a short somewhere, thus the intermediate issues. Here is a photo of the wires coming out of the harness then to a connection relay. Behind the metal are the fuses but at work so I only had this photo on my phone. If I remove the wire hardness and fuses from the cab do the back sides show which wires go to which fuses?

 

1) Does the engine crank but not start, or not even crank, when the fuse is blown?

2) If the 30A fuse lasted two minutes before blowing, what system in the truck could have been pulling more than 30A after the engine started? Battery while charging?

3) If a short-circuit is causing the fuse to blow, replace the 30A fuse with a short and look for smoke.

 

Please disregard the above advice…brilliant….

the ignition switch should not be wired to the same fuse as the gauges regardless of fuse size…


It’s still not wired correctly…

Squirrel already said it, open up the harness and draw us a picture of how it’s wired now, then we can work on making right.

 

There should not be a fusible link on the S terminal at the starter, and hopefully it goes to the S terminal on the Ign switch not the ignition on the engine(coil)

 

Please let us know you are joking...

 

Probably not I've seen guys in the shop use that method for semi trailer lights way too many times.........................

 

Yeah I’ll try to track all the wires and limit starting it till then. It’s 90 with like 100% humidity here in Houston so may take me a while.