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1968 Complete Electrical Failure

Mosesatm

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Jan 18, 2005
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Yesterday I was at a stop light, waiting for it to turn green, and the car just died.

I have nothing. No lights, flashers, horn, gauges, starter. Absolutely nothing.

The battery is good because it will turn over the starter when jumped across the solenoid.

I have power to the ignition switch but don't seem to have any to the fuse box.

Is there a master fuse that covers everything electrical?:confused:
 

franklinair

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Mar 1, 2007
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I'm taking my wiring diagrams home tonite so I can decipher your quandry.
There is not a 'master' fuse.
Some circuits are powered thru the ignition switch,
while others are independent of the ign switch
(headlites, brake lites, interior, etc.) ALL power branches out from the solenoid,
thru connectors & splices to their respective functions. We've just gotta locate the point of power loss.

Neil
 

CougarCJ

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Jul 17, 2006
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Arlie, start with the battery, battery cables, and starter solenoid.
 
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Mosesatm

Mosesatm

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Jan 18, 2005
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Just came in from the garage.

Pulled the ignition switch and jumpered from the main power terminal to the accessory terminal. Dead short to ground. Great, that lead only goes to a hundred different items!

With the jumper in place I removed all the fuses and still had a short. I then pulled the 2 yellow wires from the circuit breaker just to the left of the fuse box and a dash light came on, as did the overhead console light. I think I found the short.

Anyone know what that breaker is for? It's to the left of the fuse box and lines up with the bottom fuse. I'm hoping I can install an aftermarket in-line fuse and bypass it.

Thanks!

Edit to Add:

Looks like it's part of the AC system so I'll unhook the leads for now and see if that fixes everything (except the AC) tomorrow.
 
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franklinair

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I believe the relay you see is power for the compressor clutch: power goes from the relay to the thermostat mounted on the evaporator, and then to the compressor clutch. The theory being that when the evaporator sensor is cold enough it opens, disengaging power to the compressor so as not to ice-up the evaporator.

Neil
 
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Mosesatm

Mosesatm

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Ok, that wasn't the problem. I must have moved something or touched something and now everything is dead again, even with that circuit breaker unhooded.

Damn, this is fun!!!

Anyone want to buy a car.......cheap?
 

franklinair

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Arlie; What DOES work? Anything? I'm looking for clues as to what systems are thru the ign. sw. versus systems that are independent such as headlites, brake lites, interior lites, etc.

Neil
 

rvrtrash

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Apr 25, 2003
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Anyone want to buy a car.......cheap?

Arlie, how much? Just kidding! In a situation like this, I would check the main power wire into the fuse block to make sure it isn't loose or corroded, and then work out from there. I would be surprised if it's a dead short to ground that's causing the problem. If it was, and not protected by a fuse or circuit breaker, the fusible links in the terminals at the solenoid would melt and you'd have no power anywhere. I'm back from my rafting trip now and standing by to lend assistance if needed.

Steve
 
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Mosesatm

Mosesatm

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Arlie; What DOES work? Anything? I'm looking for clues as to what systems are thru the ign. sw. versus systems that are independent such as headlites, brake lites, interior lites, etc.

Neil

Nothing works.

The bottom fuse socket is hot and the socket above that one is hot, (I learned that the hard way) but they are not part of the accessory circuit, and since they are hot I figured the flashers would work since one of them is the flasher circuit, but no, they don't even work.



All the other circuits and fuses are dead.
 
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Mosesatm

Mosesatm

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Arlie, how much? Just kidding! In a situation like this, I would check the main power wire into the fuse block to make sure it isn't loose or corroded, and then work out from there. I would be surprised if it's a dead short to ground that's causing the problem. If it was, and not protected by a fuse or circuit breaker, the fusible links in the terminals at the solenoid would melt and you'd have no power anywhere. I'm back from my rafting trip now and standing by to lend assistance if needed.

Steve

Steve, I didn't know there was a main line going to the fuse block. I thought they were individual lines. I'll pull the block tonight. Fun, fun, fun.

Did I say cheap? Tomorrow it may be real cheap!
 

rvrtrash

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Steve, I didn't know there was a main line going to the fuse block. I thought they were individual lines. I'll pull the block tonight. Fun, fun, fun.

Did I say cheap? Tomorrow it may be real cheap!

Arlie, there should be a main power line that comes in for the stuff that has power if the key is off and another line or lines for stuff that only works when the key is on, plus all the individual outputs. From your original post, I gathered you had absolutely no power. One thing you can do if you think the problem is a short, with the battery disconnected, is take an ohm reading from the outputs of the fuses to ground. That will show you if you have a short on a circuit. With the power appearing and disappearing though, it sounds like a bad connection or broken wire. The places most likely are the wire at the starter solenoid, the connection at the fuse block, or there is a flat, 4 wire plug under the dash that carries the main power wire into the under-dash harness that might be loose or corroded. Good luck, and let us know what you find as you go along.

Steve
 

franklinair

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This may seem overly simplistic, but what about verifying the negative circuit from the battery, starting with the battery terminal, ground cable connection @ the engine block, and a good ground between the block & chassis.
Meanwhile, I'm looking over my diagrams.

Steeeeeve, help!!

Neil
 
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Mosesatm

Mosesatm

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It keeps getting more and more interesting.

I now have power to all the fuses, except the center one for the dash lights. But as soon as I plug in anything I lose all the power to all the fuses.

For example, as soon as I plug in the wiper switch connector I get zero volts to all fuses, but if I unhook that connector full votage returns to all the fuses.

It's the same issue with the other gauge connector. As soon as I connect it I lose all votage to all the fuses. HVAC fan same results.

Steve, since I have full power until I connect something I think the power wires are OK, at least to the switch and the fuse block. In my limited brain it seems to me that it is after the fuse block that it all goes kaflooey.

I think I'll crawl under the car and change out the ground cable(s).

This one has me completely baffled.:confused:
 

rvrtrash

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It could very well be a ground problem. Check all your connections but I'm still leaning toward something in the main power wire. OK, this is going to get deep and sound weird, but bear with me. If you have no load on a power wire (nothing plugged in) you will read full voltage with a digital voltmeter even if there is only one strand of the wire still connected or a break in the wire that is just touching. This is because the digital meter has such high impedance and uses virtually no current to measure with. As soon as you plug something in though, the break in the wire or bad connection acts as a high resistance, and the point you're measuring at, downstream from the break, becomes a virtual ground. As there is no significant current flow past the break or connection, your circuit won't function and you'll read 0 volts. What I would like you to do, after checking the ground connections because that's easy, is stick a thin needle into the power wire at the solenoid, just past the fuseable link and measure the voltage on the needle both with something plugged in and not. If the voltage is the same, the wire is ok at that point. If you have someone that can help you, you can have them reading the meter at the fuse block while you wiggle the wire at the solenoid and see if the meter reading fluctuates as an alternative. Go to the 4 prong plug and measure both sides of it the same way. Measure just before the connection at the fuse block. When you find a place where the voltage changes, you'll know what area your break is in or connection is bad. We'll get there yet.

Steve
 

J.Bart

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Feb 12, 2003
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800
from my experiance with cars and their electrical systems: when things act crazy and don't make sense it seems to always be a grounding issue.
sometimes i'll take a jumper wire direct from the battery negative to one wire of my tester and then see where i have power. sometimes things start making sense and i find the bad ground wire from there.
 
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Mosesatm

Mosesatm

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Success!

I don't know if it's complete success yet but at least it's a start. Who knows what will happen when I put the dash back together.

Steve, I think I did what you recommended but in my own funky way. I ran a wire from the battery directly to the main hot terminal on the ignition switch (replacing the big yellow wire), bypassing all the internal wiring. When I put the switch back together and turned the key the engine turned over! I don't know if anything else works because literally EVERYTHING else is disconnected.

Tomorrow night I'll start reconnecting things one at a time and see if it's fixed.

I guess I'll need to replace that wire with something more permanent because driving with an extension cord from the engine compartment, through the driver's window, and into the dash seems a little uncouth; although I do live in Texas, and it would make a great anti-theft device!
 

CougarCJ

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Good, some progress

Good, some progress, now you get to start doing what I like to call 'Calculatus Eliminatus'.
Which is Latin, meaning 'find out where it's not'.
 

rvrtrash

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Apr 25, 2003
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Believe it or not, I actually started to suggest running a new wire and then erased it, deciding to go the other way instead, because my gut tells me the problem is within a few inches of the fusible link at the solenoid. Try my method before you get to far along on replacing the whole wire, because soldering in a 6" pigtail is a lot easier than replacing the whole thing. I'm glad we're on the right track though.

Steve
 
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