Glad you had spares to get you home. Had a similar issue with my lights getting blown - like you on my way home. Always had fuses with me but finally figured out it was the dang brake light switch doing it one night.
A thought would be to clean the fuse terminals and put a new 30A fuse in. Turn on everything that you would run through the fuse at night and see what the amp load is. That would give an idea of how hard the fuse is working. If it is close and the wire gauge is adequate then it may tolerate a slightly higher fuse to give a capacity cushion. Given that there are a lot of hours on the car then the odds are that all is good. Drive the car in the daytime with the headlights on to see if the fuse was a one time event or if there is an issue(s). Daytime will be safer.
The story I heard, most glass fuses are made "you know where" now, and the ratings stamped on them are only loosely related to amperage they will blow. Junk. He told me to use good NOS Buss or Littlefuse.
That's true for resistive loads but not inductive ones. As to the addressed problem, I won't bring up the whole 'which circuits should be fused and which shouldn't' as I've flogged that elsewhere and it seems to fall on deaf ears, but I will make two comments... One, the fuse size is too small. To prevent nuisance tripping, fuses should be sized at 125% of the connected load, or to reverse that, the load should only be 80% of the fuse size. This is standard practice. So in reality, a 20 amp fuse should only have 16 amps connected. Remember, a 20 amp fuse is supposed to blow at 20 amps. As these have a +/- tolerance, the actual trip number will be 'about' 20 amps. Just his lighting and fuel pump get him close to 16, add in ignition, OD solenoid and brake lights and he's probably been lucky. Two, I WOULD NOT install a self-resetting circuit breaker the way the wiring is currently configured. As any Hot Rod hoodlum worth his salt knows, the easiest way to produce a sharp backfire and/or remove all the packing from your muffler on a non-efi vehicle is to simply turn the key off for a few moments without letting off the gas first, then turn it back on...Ka-BOOM! Do you really want a device installed that can do that automatically and without warning? Would you get enough of a backfire to lift the blower? I wouldn't want to find out....
A few years ago dealt with a similar issue on a original 63Chevy II The problem was at main Harness Plug (Engine side ) on the Chevy II were they meets at the firewall & fuse panel on the inside.
I had a similar episode 40+ years ago with a '69 Ford on the way home from an interstate race event. Because we were travelling on poorly illuminated country roads I fitted extra spot lights for this trip and ignorantly didn't upgrade the circuit. Sure enough at ~2am in the middle of nowhere everything went out just like Squirrel's did. I didn't have any spare fuses so we were stranded there for while and then out of the blue the lights came back on. Fortunately Fords have a 30 amp bimetal overload in the circuit that cooled and reset itself, no more spot lights for the rest of that trip and a relay circuit fitted when we got home.
Hello, As old or as new as our teenage/20 something hot rods and station wagons were at the time, similar episodes of the electrical system just quitting was prevalent. Who knew that our pristine cars would somehow give up and make us pull over to the side of the road, wondering, what the $#%@. But, after the first time, a replacement fuse was put in place and then from that point on, we all carried a small sliding metal fuse boxes with the main fuse and a box of general fuses for everything else. It was not a nice thing to be stuck on the side of a road, in the dark. One time it was next to a cemetery in East Long Beach and it was not a nice place to get stuck. Especially after we made a wonderful run down the straight-a-way, just before it happened. Jnaki At the time, all worries about blowing the motor, a bent something just stopped the motor. But, as cooler minds did some thinking and testing, the good old fuse envelope was the answer. Afterwards, the little sliding metal fuse box was a mainstay in the glove box of every vehicle. It was hectic and puzzling at the time and thoughts went to a step by step search for the culprit. The excitement and a little anger was not always the best thing for cooler heads. Then after the incident, the whole thing became a laughing matter and chuckles among friends were vocalized: “It was payback for disturbing the quiet zone on Cherry Avenue.” “The place is cursed…” (only if you lose) etc.
It makes a very loud noise in the exhaust. I learned that on my 55 (it had this blower on it before I built this car). The ignition switch got loose, and a few times it lost contact for a second or two....engine cut out...then BOOM. Good point, thanks.
Another thing I thought of....when I build this car, I had planned to use it on Drag Week, but not to actually drive it TO Drag Week....or much else. Somehow, it got 23,000 miles on it. I never would have thought....
I think the right answer is a 30 amp fuse and separate fused circuits for headlights/ignition/horn, etc. There have been a couple of comments how poor grounds or a corroded fuse terminal would increase resistance causing the fuse to blow. This is incorrect, and simple to understand why. We all know if you connect an inline fuse between the positive post to a negative post - poof - instantly blown fuse. That is a situation with very low resistance, like a short. A very high resistance or poor ground will make the load (headlights for example) not work or burn very dim due to insufficient voltage, but it will not blow the fuse. In Jim's case you could add up the wattage (power consumption) of the lights, ignition, fuel pump and other power draws and probably find that a 20 amp fuse was really borderline for a single main fuse. Its possible that touching the brakes with everything else on was enough to blow the fuse. The reason this happens is because adding another load (brake lights or turning on the radio) puts another resistive load in *parallel* with the other resistive loads, causing the overall circuit resistance to decrease, causing current draw to increase. Which will cause an overload and blow the single fuse feeding all the loads. Hence separate fused circuits. Adding a resistive load in *series* with an existing load does the opposite, increasing the overall resistance of the circuit and lowering current draw. Its not entirely intuitive, but is consistent with the math
I had the exact same thing happen to me some years ago, but I was on my Harley! Successfully got it to the shoulder, lights came back on. I could never find anything thing wrong. But after that adventure, I added seperate running lights on a complete different circuit , wired directly to the battery! Just my solution! Bones
Just went thru something similar. Finally found it was a wire with the insulation barely pulled back from the terminal in a dash lamp. It would ground out every so often against the metal lamp holder and pop goes the fuse. Looks like you have some metal lamp holders in your setup. The clue was it only happened with the lights on The suggestion to go for a daytime drive with the lights on, is a good one. If it was a Model A, I would say to check the horn circuit as it is hot all the time and the horn button makes the ground Good luck
Don't laugh. @Rocky @sodbuster and @jangleguy and I fixed Chris' sedan with a chewing gum wrapper on a dark road after the 1st KS&P Meet
I really don't think it was a short that caused it to fail....there just doesn't seem to be any evidence to support that idea. And with the fuse size, age, and current load, and it's appearance, the failure is explained without needing a short.
It was funny for me as I had a buddy following me one night - when I hit the brakes the lights went out and I went for the curb. The buddy said - yep I saw you brake and then lights out - we changed the fuse and I disconnected the brake switch. Tested it out the next day...shabang !
My 66 Chevy II was all factory wiring and did that same thing on a winter night (but I had plenty of light) I would replace the fuse and with in a few miles it would pop again and it came down to not having any more fuses in my glove compartment so I started taking them from the fuse block and of course not too many in that. I made it home (I was almost 17 years old back then) and looked for days trying to figure out what was going on with my Deuce finally I took a look inside my voltage regulator and found what was once a small critter frog or who knows what it was when it made it's way into my voltage regulator (it was a used regulator from Marquis Junk Yard, I could not afford new parts back then, it had only one bolt holding the top on and I never looked inside it until that day) and so I found my problem and replaced it with another. I guess for some freaky thing every time I hit a pot hole it would make the critter move and in doing so pop my fuse. But I'm sure Mr.Squirrel's wiring harness is not factory any more. Soo just maybe you have a critter or a small gremlin making it's new home somewhere in your wiring harness or ? It's just a thought! 1Nimrod
I would take a look at the sealed beam headlights themselves. Had a light switch burn out once. Replaced it , drove about a week, everything fine. Once I kicked the high beam, poof, there goes another switch. High beam shorting out in the headlight .
I hope it's a spent 22LR cartridge? As you know it might wake you up in a very scary way my friend... 1Nimrod
That's why I like to scrounge in the older junkyard's and find the old USA made BUSS Fuse's. Chances are you can get them FREE or for a few $$ most the time the Counter Person doesn't have a clue what they are and just let's me have them for FREE especially if I buy something else from them. I also get little light bulbs of all kinds the same way. The Good Old USA made part's are always the best and when I find them they go in my part's box for when and if I ever need them. Thank You Squirrel for your many Teachings. 1Nimrod
I have a hard time believing the great minds at GM would have run all that off of only one fuse. Granted the oldest car I ever had was a 62 Cadillac limo it had a boat load of fuses in it. Pull off the fuse box from the fire wall and look at the back side of it. I’ll bet you find the problem. I have never seen a headlight switch that had a fuse for the headlight power. Something is going on. I’d hate to see you let the smoke out and loose the car. When I worked at the Buick dealer I had a 73 LeSabre get towed in from Gary (IN) to me that the guy used a 22lr for a fuse. It did not end well for the fuse box or his leg. He fragged his own leg. I still laugh about it 30 plus years later. I saw a lot of fun stuff!
You should have seen what was under the dash of my Ford, not nearly as sophisticated as an old Chevy II, but really primitive. Fuse holders all over, fuses on the HL switch, what could possibly go wrong?
Funny you say that Marty. Rooftop HVAC commerical package units. The "disconnect" usually has 3 copper ended Bussman fuses. In a pinch .. we have used cut copper pipe. Or maybe we didn't. Sometimes its just an after 5pm on a Friday decision.
When I saw that fuse it reminded me of a 1965 Chevy I bought about thirty years ago and when I looked at the fuse box someone had wrapped the blown fuses in the foil paper that used to come in cigarette packs back in the day to keep them working.
Ahhh, but it is a resistance, and it is a resistance that causes heat, sufficient heat to cause the fuse to fail. If you did the same thing with just a wire, no fuse, the same thing would happen to the wire. Why? Because of resistance. There is a difference in potential between the positive and negative posts, and any connection put between them will cause a current to be drawn in an effort to fill that difference in potential. In the case of a fully charged 12 volt car battery, you pretty much cannot connect any cable of sufficient current handling capacity between the posts to handle the demand without failing, due to resistance. And if you could the battery itself would probably melt down. Resistance causes heat, period. Why does a short cause a wire to fail? Because of resistance in the wire itself. A short circuit places a very high load on the wire, and though you think it's a very low resistance, it is the resistance in the wire that causes the heat the results in it's failing. A device with a bad ground doesn't place a full load on the power supply, so it doesn't cause heat or cause the fuse to blow, that part of your post is correct. But that is a very different situation than a high resistance between the device (load) and the power supply. Different devices place differing amount of load on the system, a small glove box light bulb for instance places very little demand, and a starter places about the greatest demand in an automotive system. Whatever the current demands of the device, if there is resistance between the load and the power supply heat will be generated at the point of resistance. That is a fact. If the resistance is the fuse, and the load is heavy enough, the fuse will fail. If the resistance is the size of the wire, and the load is heavy enough, the wire will fail. If the resistance is a connection between a terminal, and the load is heavy enough, the wire connected to that terminal will fail. In the case of Jim's failure, if the resistance between the fuse and the clips connecting it to the fuse panel is great enough, and the load heavy enough, heat will be generated in the fuse itself; and if the heat generated gets high enough the fuse will fail. And it's all due to resistance.
I've told this story before but it's worth doing again. I bought my 67 c30 flatbed from one pissed off mofo. This truck had an intermittent short that would blow the tail light circuit. Poor guy tried everything to remedy this problem, almost. I figured out that if I did not use the turn signals, I never had a problem. He put a new four flat wire from fuse box to the rear and new tail light assemblies. Me and a twelve pack of Miller Light sat and pondered the issue. I decided to pull the steering wheel in the morning when I was sober. Sure as hell, there it was. The flat steel spring that pops the emergency flasher button back out had come loose and was laying there ready to short out every time I used my turn signals. Put it back in with a little glue on each end and never had a problem since.
This is SO DANGEROUS!! Everybody knows you either run all the fuse heads on the SAME SIDE, or you alternate. Plus, he's got 2 that are ALL THREAD. Dude's gonna have a bad time...
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