smoking wires

Slik

Slik

Member
OK - I thought the electrical on these was pretty basic but ......

Car was running fine, parked it outside in the sun for awhile, couple hours later I started it and backed it into the garage, once started and running the wires started smoking. I immediately disconnected the negative cable (almost had a heart attack as I scrambled to remove the floorboard and mat and get the wrench to disconnect).
Smoke was coming off of the yellow/black wire from cutoff to junction box, yellow wire from starter to junction box and after removing the dash I saw the plastic on the nuts holding the ammeter wires were melted - was a new ammeter. When I pulled the ammeter the needle was blown off the internal stem.
Like I said up to this point the car was running fine. I replaced the dash wiring and the wiring harness from cutout/starter to junction box with new harnesses. I also added a quick disconnect at the negative battery terminal. I was very careful when I was installing the new harnesses and made sure all connections where correctly wired and clean and tight.
I put the needle back in place on the ammeter and reinstalled. Cleaned cutout terminals and made sure they were correct. Made sure ammeter and ignition switch were not shorting out to gas tank (put in rubber padding).
Connected the battery and both harnesses fried again. I never even turned on the ignition switch - just connected the battery.
I'm left to believe it is either the cutout or the ammeter - a repo (which had the needle blown off again). Ideas ? Why would leaving it out in the sun potentially cause this ? Cutoff was not new but up to that point generator was showing a good charge of 10 amps when revved up slightly. Potential other problems ?
 
cutout is probably stuck. sun was probably just a coincidence. a new ammeter cant hurt either.
should really install a fuse, thier invented to protect the wiring in these instances...
 
Will definitely be ordering a fuse (when I order new harnesses - again).
Is there a way to test the cutout ? I have about 5 others that came with the car.

I should mention that the car is stock 6V, positive ground.
 
i would personally ditch the standard cutout and go for the diode version or the best version would be the one with an electronic voltage regulator inside. From the outside noone will ever know as they are physically identical to the stock cutout.
 
Cut outs stick all the time and usually don't cause a dead short. When they stick shut it will cause the battery to drain down overnight. I think your ammeter is shorted to ground internally or the junction box mounting bolts are shorted to the firewall. The ammeter can be taken out of the circuit and connect just the two wires together. The cut out could have been damaged also from the short but that can be checked after you fix things back up. Fix the wiring and leave the yellow wire off the starter as that's the main feed. With the key off and battery connected put a testlight in line from the yellow wire to the starter post. It should not light showing no draw.. An ohm meter is also ur friend on testing circuits. Then touch it to the post and it should not spark if all is good reconnect . Get yourself a new ammeter I think that's where ur problem lies...

Never rehook a fried /// repaired circuit back up without some kind of protection device inline.. Like a temporary circuit breaker or fuse to protect it from refrying till ur sure it's right
 

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Slik said:
Will definitely be ordering a fuse (when I order new harnesses - again).
Is there a way to test the cutout ? I have about 5 others that came with the car.

I should mention that the car is stock 6V, positive ground.
Click to expand...

Use a Multimeter set on Ohms to check each circuit including the cutout for continuity. Should be no continuity when turned off. Cutout should have no continuity until the generator starts charging.
Bill
 
Let's follow mitch's drawing and see what is happening.

We know that the electricity comes from the battery, through the wires and equipment and back to the battery.

Only two wires were burned yellow and black yellow and it's important to note that the engine was not running the second time so the generator was not supplying electricity.

The battery goes to the starter, the yellow wire then goes up to the junction box, to the ammeter, through the ammeter, changes color to black and yellow and goes to the cutout.

Cutout.htm


If the problem was a short in the junction box, back to the battery ground, only the yellow wire from the starter would be burned. If the problem was the ammeter shorted, still only the yellow wire from the starter to the ammeter.

So lets keep going, following the yellow black (YB) wire we end up at the cut out.

My guess is the cutout is shorted internally to ground. Possibly the insulator is worn out.

Take a meter or test light, remove the wires from the cutout. Place the meter/lamp in line with the YB wire and the cut out. Connect the battery and if the light lights or the meter shows anything the cutout is bad.

Replace with new or original from Bert's.
 
The cutout should have a thin insulator on the generator side, and a thicker insulator on the terminal box side with the yellow and black wire connected to it. The horn/lights wire is also connected to it. Make sure the screws on both sides aren't too long and shorting internally. Also make sure the wire terminals aren't touching the cutout case.
 
Have no idea where your short is but YOU SURE DO HAVE ONE!
Rule #1 (from an old retired boat accident investigator)
Power off... and check each circuit with Ohm meter for continuity. Will not take long to find a short to ground and no damage to your harness etc.
My bet is a grounded AMP meter but only a guess.
 
Al, I totally agree.... Just a tip but next time for someone who has a problem like this and doesn't have fuse, just grab a pair of wire clippers and clip the hot yellow hot lead ( small wire, not main cable) and that will pull power from everywhere except starter. You can then go down to your local auto parts and get one of the 30 amp fuse holders and put them in line. I would suggest soldering and heat shrinking the connections. Get the type that has the waterproof flip lid is my preference.

Hopefully he found the short.
Larry
 
larrys40 said:
Al, I totally agree.... Just a tip but next time for someone who has a problem like this and doesn't have fuse, just grab a pair of wire clippers and clip the hot yellow hot lead ( small wire, not main cable) and that will pull power from everywhere except starter. You can then go down to your local auto parts and get one of the 30 amp fuse holders and put them in line. I would suggest soldering and heat shrinking the connections. Get the type that has the waterproof flip lid is my preference.

Hopefully he found the short.
Larry
Click to expand...
GREAT TIP, LARRY!!!! JUST CUT THAT DANGED YELLOW WIRE AT THE STARTER SWITCH, QUICKLY!! That might save a car from burning to the ground!!!
AND, DON'T TRY TO YANK THAT YELLOW WIRE OFF WITH YOUR HAND, IT'LL BURN THE CRAP OUT OF YOU:eek::eek::eek:
Bill W.
 
Pay attention to ALL the clues.

My first thought was exactly the same as Mitch's, until I read where Mike mentioned the wire going to the generator was also burned. Then I started thinking about a missing insulator on the cutout, which would be a direct short to ground.

Now I just went back and reread the first post and realized the engine WAS RUNNING when this happened, so you had power from both ends of the circuit. So that means the short could have been anywhere along the circuit. So now I'm back to thinking Mitch most likely mentioned where the problem lies.:)

If the engine wasn't running, then the short would be at the end of the burned wires, but with power from both ends, it could be anywhere along the circuit.
 
Problem does appear to have been the washers on both sides of the cutoff. One was old and dry rotten and most likely when I started the car after it sat in the sun for some time, the washer literally crumbled apart from the vibration.
Wiring has been replaced (dash and term to gen). New quick disconnect installed and a fuse added. I'll install the new ammeter this weekend and hopefully all will be solved. I've used the down time to also "tweak" some other minor issues too.
Next question - I'm considering changing the cutoff to a diode type. I bought the kit to convert and old cutout (I have several) BUT how do you get the cover off ? I am not seeing any spot welds or any kind of notching to hold the cover on but it doesn't want to budge. Ideas ?
 
Wire brush the bottom of the cover and you should see 2 spot welds on the very edge IF it's an original cutout.
Repro's simply bend a couple dimples to hold the cover on.

I use a very sharp center punch to split the spot welds, then pry against the mounting feet and cover with a large flat screwdriver to lift the cover. Of course the screws for the terminals must be removed FIRST.
 
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