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Technical The Main Fuse

Discussion in 'The Hokey Ass Message Board' started by squirrel, Jun 13, 2021.

  1. Truck64
    Joined: Oct 18, 2015
    Posts: 4,626

    Truck64
    Member
    from Ioway

    Headlights themselves aren't fused for this reason, are they? Factory OEM?

    A resetting circuit breaker is incorporated into the headlight switch itself. They can get wonky or intermittent due to age and high resistance, but they won't leave you searching for spare fuses, in the dark.

    If the resistance goes up, the current might go down, but the heat goes up, doesn't it? That's what resistors do, they get hot. Where did the current go?

    Halogen lamps draw more current than tungsten, but if you pencil it out it is well within normal specs for the wiring.

    If headlight switches are smoking or the breaker is tripping there are other problems. Like .. high resistance! I run a 12 volt generator and script halogens and the headlights work well even without relays.
     
    1Nimrod likes this.
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 48,682

    squirrel
    Member

    That's the plan, right now.

    The fuse holder is clean, but the fuse itself is an old one that was a bit dirty and corroded.

    Also...I forgot the fuel pump is also part of the continuous load. I think it draws a few amps.

    Thanks for the comments, lots to think about.
     
  3. Wrench97
    Joined: Jan 29, 2020
    Posts: 419

    Wrench97

    If you go with a breaker use a type 2 or type 3 the autoreset type 1 can cause a lot of damage while constantly resetting itself.
     
  4. AHotRod
    Joined: Jul 27, 2001
    Posts: 11,358

    AHotRod
    Member

    Glad your OK Jim, spooky adventure.
     
    1Nimrod likes this.
  5. David Gersic
    Joined: Feb 15, 2015
    Posts: 2,383

    David Gersic
    Member
    from DeKalb, IL

    Fuses are heat devices. Your fuse got hot. That can be from a short or overload, but a new fuse would pop as well if overload was the cause. A solid short would also pop it immediately. Intermittent short may not, and can be a bitch to find.

    More likely it came from poor contact between the fuse body and clips. If the clips are clean and shiney, put a new fuse in and be happy.
     
    pprather and 41 GMC K-18 like this.
  6. impala4speed
    Joined: Jan 31, 2010
    Posts: 250

    impala4speed
    Member

    Same thing happened to me on my old Yamaha 650. Nice ride on a bright sunny afternoon out on a country road somewhere. Bike just died. When riding a 40 year old motorcycle around you carry extra parts, not the least of which are spare fuses. Put a new one in and good to go. Never blew again. Glad it worked out for you Squirrel, especially being at night.
     
    1Nimrod likes this.
  7. As already said a poor connection between the fuse and the clips would cause a high resistance which will reduce current flow, fuses blow do to excessive current flow.

    Jim, everything goes through that fuse to the car? Am I understanding that correctly?
     
    oldengine likes this.
  8. MCjim
    Joined: Jun 4, 2006
    Posts: 215

    MCjim
    Member
    from soCal

    What I use. IMG_5254.JPG Same as main breaker on Electric start Harley...30 amp
     
  9. landseaandair
    Joined: Feb 23, 2009
    Posts: 4,436

    landseaandair
    Member
    from phoenix

    Is this an original Chevy II fuse block? I've never seen a "main" fuse before. Just labels like - stereo, radio, heater air cond, back-up brake al, wiper motor, tail lps, instr lps. Think I only had a couple '62 or 63s so maybe their an oddball and I didn't notice.
     
  10. 1ton
    Joined: Dec 3, 2010
    Posts: 537

    1ton
    Member

    I'm also going to go with the old dirty connection between the clips and the fuse. It seems that the fuse in question has not been touched in years. Replace it with a 25 amp and I'll betcha 10 bucks it'll never happen again. Although it would be nice to find an actual short or something so you know that there was an actual problem and not an invisible gremlin fucking with you.
     
  11. trollst
    Joined: Jan 27, 2012
    Posts: 2,018

    trollst
    ALLIANCE MEMBER

    I'm with the fuse was tired, old style fuses are like that, they just fail at tyhe worst times. I doubt if you put in another 20 amp, it'll fail soon, but personally, I think 20 amp is not enough to safely power the car, it looks like you're running on the ragged edge of the fuse's capacity, when I wire stuff, I find the headlites alone will warrant a 20 amp fuse. Especially if you run halogens, as I do in my 36. Good luck.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 48,682

    squirrel
    Member

    Some of the wiring is original, but the main power wiring and all the engine stuff is not. It's not an original fuse block, it's an aftermarket fuse holder. The terminals are not corroded, or old. The fuse was a bit corroded, and old.

    wiring07.jpg

    This is the under dash harness, when I was piecing it together.

    wiring06.jpg
     
  13. Truck64
    Joined: Oct 18, 2015
    Posts: 4,626

    Truck64
    Member
    from Ioway

    My point is headlights weren't ordinarily fused, and for the reason you described. Pretty much everything else is to include running lights brake lights, and turn signals, dash, etc. The headlight switch itself will have an internal breaker.

    Even with a thermal headlight breaker, it does tend to get your attention! The advantage is they will sometimes just "blink" momentarily and come back on, instead of "lights out, how's your night vision?" It's a safety issue.

    I don't believe headlights are (rarely?) EVER fused as part of the OEM wiring. Could be wrong, often am.
     
    F-ONE, 1Nimrod and squirrel like this.
  14. landseaandair
    Joined: Feb 23, 2009
    Posts: 4,436

    landseaandair
    Member
    from phoenix

    Can't say I've seen any older cars with protection on the main feed side but think on aftermarket harnesses they go with a 50 amp? Maxi Fuse Or fusible link like a newer car. Maybe it needs an upgrade?
     
  15. Truck64
    Joined: Oct 18, 2015
    Posts: 4,626

    Truck64
    Member
    from Ioway

    Right, so maybe that's a pretty good reason why headlights don't run through fuses, they have their own integral thermal breaker?

    Whatever causes fuses to blow out might be interesting to determine, but headlights shouldn't ever be part of the fun & games.
     
    VANDENPLAS likes this.
  16. landseaandair
    Joined: Feb 23, 2009
    Posts: 4,436

    landseaandair
    Member
    from phoenix

    Did the pitch black thing at speed once. Got an old baja bug for cheap and was going through the desert on a dirt road at about 50 in the middle of the night with two buddies and then no power or lights. Held the wheel straight and slowed down without hitting anything. Got out and used a lighter? to see, no cell phones back then. Had a cheap plastic multi fuse holder and someone had the ign., radio, headlights and KCs all on one circuit that melted down. Moved some leads around and back to chasing rabbits and bouncing through ditches. Traded it for a '74 Nova the next day.
     
    1Nimrod likes this.
  17. oldolds
    Joined: Oct 18, 2010
    Posts: 3,153

    oldolds
    Member

    I would guess you were running right at the edge of the fuse capacity for quite some time. Personally I would not run a main fuse for the whole car. Head lights and fuel pump on dedicated circuit for each one. Relays, on at least the fuel pump. Because of power draw. On headlights usually benefit from a relay as well. Ignition system with a fuse. Relay there could drive you crazy if it gets weak.
     
  18. Those "lonely highway" trips are some of the most mellow drives you can take......
    until they aren't. :eek:

    Not exactly the same thing but..... your story reminds me of the time 3 of us were in the middle of the New Mexico boonies at half-past midnight when we suddenly heard the sound of silence and rolled to a stop.
    I think we had lights but no flashlight or tools to speak of. Fortunately, it turned out that the primary distributor wire had fatigued from being knocked around for years and was easy to diagnose and fix. But it was creepy scary for a moment looking to the horizon in every direction and not seeing even a porch light. :cool:
     
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  19. 1oldtimer
    Joined: Aug 21, 2003
    Posts: 7,999

    1oldtimer
    ALLIANCE MEMBER

    That one looks like it popped pretty hard, usually don't see too much spatter on the glass. I would keep more spares and try a circuit breaker (auto or manual). To me it sounds like it shorted momentarily.

    Also I know you know, but those holders can get hot and the backer material can become compromised.

    Here's what happened to my '41 after I got it back on the road.
    fuse panel-1.jpg
     
    Last edited: Jun 13, 2021
    1Nimrod likes this.
  20. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,560

    Blues4U
    Member
    from So Cal

    The fuse obviously failed due to heat. What caused the heat? Most are focusing on excessive current draw, but a few have mentioned corrosion buildup between the fuse and the holder clips, and that's what I'm going with as well. Heat always develops between the load and the point of resistance. Corrosion of the clips would increase resistance, causing heat in the fuse itself, until the point where it failed. Removing the failed fuse and inserting a new one refreshed the contact and it now it works fine. Until the next time. I'd probably attempt to clean any remaining corrosion on the clips, and I think you're good to go, but keep a fresh fuse in the glove box or tool kit. A circuit breaker would also be fine.
     
  21. flatford39
    Joined: Dec 3, 2006
    Posts: 2,790

    flatford39
    Member

    I tell you as simple as a blown fuse sounds I learned alot here about them. Well worth the time reading. You have to respect the members of the hamb for their opinions.
     
    Shalamo, 1Nimrod, bchctybob and 2 others like this.
  22. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,077

    Mr48chev
    ALLIANCE MEMBER

    First question I have to ask is what did you change electrically since Drag week?

    If the car has Halogens I would put relays on the headlights. Not running the power though the relays through the main fuse if you indeed reuse it.

    Then I'd get another fuse block or one with more circuits and a pair of buss bars that matched the number of circuits with and feed the buss bars with the main power feed with a short lead to each fuse with one bar being hot all the time and one being switched for the switched circuits.
    My main line of thinking is to separate each circuit to it's own fuse.

    I'm with a few others in that the sum total of electrical draw with lights on and everything running is more than the amp rating of that fuse.
     
  23. TrailerTrashToo
    Joined: Jun 20, 2018
    Posts: 950

    TrailerTrashToo
    ALLIANCE MEMBER

    I agree with most of the above. Especially the more fuses part.

    20210613 fuse block.jpg I have a 6 position fuse holder to donate to the cause. Never installed (New-Old-Blister-Pack-Stock), I went to the blade style fuses. I'll also donate all my unused glass fuses.

    RANT: Glass fuses are only better than the European pointed-end cartridge fuses (found in 1960's VW, Volvo, etc...).

    The headlamp switch pictured is out of a 1971 IH pickup - Similar to the 1960-1996 Chevy headlamp switch (Standard Motor Products DS155 or equivalent). Side note: Also used on older Bluebird school buses. If my memory serves me correctly, the headlamp circuit is independent of the parking light circuit, allowing them to be fused separately.

    EDIT #1: I don't have a pull knob to do a pin-out on this switch.

    EDIT #2: No circuit breaker in this generation headlamp switch.

    Russ
     
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  24. Beanscoot
    Joined: May 14, 2008
    Posts: 1,981

    Beanscoot
    Member

    Years ago I drove a crappy Russian car that would randomly blow one fuse. I had to take the dash partly apart for some reason, and found a quarter in there, which would randomly roll around, shorting a couple terminals.
    I made money on that repair!
     
    '51 Norm, Ned Ludd, 1Nimrod and 3 others like this.
  25. Wrench97
    Joined: Jan 29, 2020
    Posts: 419

    Wrench97

    They often are today, but it's one fuse for the left side another for the right side.
     
  26. squirrel
    Joined: Sep 23, 2004
    Posts: 48,682

    squirrel
    Member

    That's why I posted....in the hope that at least one person would think about the wiring in their car, and see if they might want to make a change.

    Nothing, except more time and miles.

    yeah, I don't think there's anything in the original wiring on the60-up GM cars that will interrupt the headlight circuit, aside from switches and connectors failing.
     
    1Nimrod, Paul and flatford39 like this.
  27. Los_Control
    Joined: Oct 7, 2016
    Posts: 737

    Los_Control
    Member
    from TX

    I just have to love @squirrel original post , They told a interesting story, A lot of people are qualified ... but they can not simply explain a issue.

    Squirrel explains a issue & we all know he will correct it. Many people really cant explain a issue.
    Just a bunch of mumbo jumbo.

    Squirrel can profit from a youtube chan, even if not racing this year.
    People care and watch and look for more.
     
  28. lippy
    Joined: Sep 27, 2006
    Posts: 5,533

    lippy
    Member
    from Ks

    I'm thinking that Benjamin Franklin era fuse could have given up the ghost.:D. I'm like Jim, if I can get another month out of something..........
     
  29. Marty Strode
    Joined: Apr 28, 2011
    Posts: 5,788

    Marty Strode
    Member

    Lippy, I like to keep a 22 long rifle shell in my old truck for emergencies, it will handle at least 30 amps.
     
  30. Wrench97
    Joined: Jan 29, 2020
    Posts: 419

    Wrench97

    What's a 22 about 100 amp with audio/visual alert?

    Fuse chart.JPG
     

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