The Stovebolt Site Forums The Shop Area The Electrical Bay New Harness almost on fire! SCARY!

My 59 went out of the garage today for a shakedown run after getting it all done. New wiring harness for the restoration. 6 cylinder with stock gauges and foot stomp starter. The truck has been running off and on in the driveway for about a week while I got things sorted out but today was the first trip down the back road.
Came home, turned the key off and parked but did not disconnect the battery as I usually do when it is going to sit. About 2 hous later, I saw smoke in the cab and under the hood!! I quickly pulled the battery cable and let the smoke out and took a look.
The wire that runs from the footstomp terminal direct to the ammeter gauge was RED HOT and no insulation left. The tape had melted and the ammeter gauge was black from the melting of the terminals on the back. Discolored the metal on the back of the gauge it got so hot. Some melted insulation (minor)on the outside of a couple other dash wires where they were touching the ammeter/foot stomp wire. The wire that leaves the ammeter going out under the hood was NOT heated so it shorted dead at the gauge from the foot stomp terminal.
I was VERY LUCKY the truck did not burn up as it was really shorted good. Now as I try and determine what could have happened I am looking for some ideas.
Seems that short was either at the footstomp terminal or the back of the gauge but I am guesing that since it took a couple hours to get fired, I may have been heating up for a while. When I came home, I restarted the truck once when it stalled and pushed the footstomp accidently right after it started but only momentarily? I would not think that would cause such a delay reaction. The ammeter was working prior to the meltdown. I wonder if they can go bad enough to short dead like it did. Power wire to the ignition switch was good and also unaffected.
What a mess. Melted tape and insulation and my brand new harness now is in need of some serious inspection and repair. Pretty scary and I sure do not want to see that smoke again. By the way the truck ran perfectly for the short run. I guess I just live right.....

had to have a ground right at the meter for that wire to fry, not at the starter - excess current was running there, where there should have been no ground possible with the key off .... did you have the heavy paper insulator under the terminals of the gauge? may have been happening for some time but never long enuff to notice cuz of disconnecting the battery

helpful hint - after doing electrical work [like a new harness] as discussed in another thread, connect the ground first, then touch the pos cable to the battery post and watch for any spark ... if seen, find the problem without letting the smoke out

Bill

Bill,
The heavy paper was on the gauge. It was a reproduction piece from one of the vendors. I suspect I either did something wrong in the installation of the new harness or perhaps I grounded that wire near the back of the gauge panel.

With the key off on the foot stomp type setup the only wire that burned was the direct line from the starter terminal to the ammeter gauge. Somehow , as you said, the power was still getting to the gauge. I m now rethinking the installation of the new harness. I used the detailed and fairly simple directions that matched the numbered wires to the specific application, but obviously something was either wrong or bad.

When I look at the wiring diagram for the 58/59 6 cylinder foot stomp, I see the current goes through the ammeter from the terminal on the foot stomp on one side, and from the ignition switch on the other. Is the feed to the ammeter (blackwire that fried) only hot when the key is on feeding the other terminal (red wire from ignition)? Or is the black wire hot up to the gauge all the time?

If I improperly wired the ignition switch allowing current to the gauge whenever the battery is connected (even with key off) I wonder if tht would cause failure after the truck was off a while?

The fact that the short was from the black wire side of the ammeter only, all the way back to the stomp starter indicates somehow I dead short grounded that wire right at the gauge? Should I be able to see power on the black wire from the stomp to the ammeter WITHOUT the key on? Does the feed go through the key to the ammeter and continue on the black wire over to the stomp switch or the other way around?

One other item I need to look at close is the METAL speedo cable at the back of the gauges. It was not hooked up yet and I justhooked it up to the gearbox after locating the right gear drive. Maybe it was spinning against the gauge terminal or wire? But it seems that the key off 2 hr later smoke and meltdown indicates power was present cuz man was that big copper wire glowing red hot when I jerked the hood open and pulled the power cable from the battery. Lots of melting tape insulation and smoke! Ralph

Ralph,

Too bad about your problem. The battery feeds the starter and the large wire that connects to the ammeter. When the battery is connected, there is constant, un-fused power running from the battery, through the ammeter all the way to the voltage regulator and to the powered side of the key switch.

Because your damage was limited to the wire from starter to + terminal on the ammeter, and not through the ammeter to any wire on the - side, it tells you, as you observed, that the short was only in the wire from starter switch to ammeter +.

You said the ammeter case itself is burned and black. To me, this would indicate the source of the short to ground. The wire melted because it was passing more current than it was designed for, and the source of ground for the rush of current sounds like it was the ammeter case itself.

Stuart

Thanks Stuart. Well that makes sense as I actually hoped that the power was feeding through the ammeter BEFORE the key as that would indicate the problem was the short at the ammeter and not (perhaps) my wiring installation.

Now I wonder why the wire/gauge was overloaded. I have a HEI Langdon coil but wired it up as instructed with 10 gauge wire and it was unaffected. If that ammeter failed just passing current with the key off and somehow grounded itself, I sure wont be puttin that back in.

I have to get this figured out so I can make sure I prevent it again. Ralph

The key is on the "other" side of the ammeter.
Like Ralph said, power goes from battery to starter switch to ammeter. Then it goes from the ammeter to the alternator and ignition switch.

You said that only the wire from the starter switch to the ammeter was hot. If the wire from the ammeter to the ignition switch didn't get damaged, it sure sounds like a problem at the ammeter.

I'd suggest putting in a fuse or circuit breaker in that line from the starter switch to the ammeter. I put a 30 amp circuit breaker on my 53 3100. It mounted on the firewall just above the starter. The benefit of the circuit breaker is that it will reset when the short clears. A fuse will have to be replaced.

regards,
Leon

you obviously can't put that ammeter back in, Ralph, it's fried!!

when you get a replacement, and replace the burned wires, put it back together and carefully inspect the lay of the wires to insure nothing metal is touching that wire or the gauge case, then do as I suggested above, hook up the pos cable last and watch for the slightest spark, there will be none unless something is shorted

Bill

I took a great photo of the ammeter gauge in the panel after I took the gauge panel out of the dash. I do not know how to put photos on an outside host yet, so if you are interested in seeing the damage PM me.

I am going to re-examine the layout this morning and try and see if I can determine a cause and effect. As the gauge only passes current, I really can't believe it failed on it's own. I NEVER saw the gauge indicate charging when the truck was running but it dropped down each time I pulled the lights on. Otherwise it stayed right in the middle.

It is very clear to me that the four terminal (two each side of gauge) gauge was grounded on the DISCHARGE side as the badly discolored case and terminal are limited to that side. It is really torched and you can see the other terminl side is still new in appearance.

If that run of black wire was shorted anywhere back towards the footstomp starter, would the damage be so evident right at the gauge or is that damage just indicative of the biggest metal to metal terminal next in the run?

The wire was REALLY cooked at the footstomp and just fell apart there but I have no real discloration of the switch. I have to think that somehow I got grounded in that wire run to the discharge side of the gauge. But I wonder how that terminal reacts if the black wire was grounded, say, half way under the dash or back towards the stomp?? The path of current stuff always makes me scratch my head. Ralph

Wow, I just pulled the gauge itself from the panel and the discharge side of the unit INSIDE the panel is fried as well. I do not know if the hard plastic "boiled" up as a result of the short or if the gauge got so hot it boiled up and then grounded out against the case. It sure looks suspect to me inside. I have a great photo if you want to venture a thought. If I have this right in my limited understnding....... for there to be so much damage INSIDE the gauge and on the OTHER side of the terminal....doesn't that indicate the ground was created there. Otherwise I guess the heat of the short could have boiled that plastic. On the other hand, I can not see where there is any metal to metal contact?

Ralph,

I think if you envision the wire from battery side of ammeter to starter switch in your mind...then imagine cutting the insulation and grounding that wire exactly in the middle of its run.

It would cook and fry and turn black only between the point of grounding and the starter switch. That is the path the current took..the half of the wire from cut insulation to ammeter would be basically untouched as it didn't directly pass any current.

Battery power was traveling from the battery, thought the connection on the starter, up the wire and into the ammeter on its way to ground. It didn't destroy anything upstream of the ammeter because the ammeter is where it found a ground.

If you shorted a wire from your BATT regulator connection or your BATT alternator connection, the wires would have cooked all the way to that point...wherever there was a dead short to ground.

Your barbecue was a freak accident. With a good ammeter wired correctly with that single fat wire to starter switch you should have no issues. This is why the industry went to volt meters..they don't series the entire potential of the electrical system...without a fuse yet!

Stuart

Well if the grounding could not have happened BEFORE the gauge then I am left with the conclusion that the gauge somehow failed. I carefully examined the underdash area where the panel and gauge are and do not see anything that would have caused the grounding.

Remember, I drove the truck, came home and parked it for a couple hours before the smoke deployment. If current is present even when the key is off, I wonder if the wire was slowly getting hotter and hotter due to?? and at some point we know the gauge failed enough to meltdown on the starter wire side. It just does not make sense that it took so long if it was a direct grounding........that should have happened within a short time I would think.
I do not know how these ammeter gauges work internally but the INSIDE of the gauge was cooked as well. The hard black plastic surrounding the metal aspect of the unit on the D side really cooked.....almost as though it could have been from the inside out. If Stuart's description of the grounding was on the back side of the gauge it would have had to be heat transfer or failure of the internal guts of the piece to be melted INSIDEof the unit.

Beyond that theory or the continuing heating of the starter wire long after the truck was off I want to make certain somehow I am not "heating up" or creating resistance somewhere it should not be. The wires on the downstream side of that D terminal were cool to the touch as I checked right away, the voltage regulator and ignition switch as well as generator wires were all cool.

I intend to fuse the line as that was too close for comfort, but I hate not understanding what caused this as it makes no sense to rewire and not have a clue. If the gauge failed or it grounded out when it was parked and not running with the key off for some time, it makes me believe I have done something wrong in the wiring installation. All the terminal connections look good, the wiring is a reproduction harness of good quality. I took the resistor out of the equation as the Langdon HEI instructions say to eliminate it. The harness wires and terminal ends for the resistor were not hooked up.

The other wire that is cooked is the temperature sending unit but I believe it was from being in touch with the starter wire near the back of the gauge in the harness behind the panel. I wondered if that wire could transfer enough heat that it melted after the truck stopped (HOT), then melted the starter wire insulation slowly until it grounded out....... Seems like a stretch but I am grasping at cause and effect. I know the temp gauge did not show hot as I was driving it was in the normal to slightly warm range. Thanks Ralph

Ralph,

On the earlier trucks with ammeter, the wiring from charging system including the wires to the key switch and anything else is located on the - or discharge side of the ammeter. The starter and battery on connected to the + or charge side of the ammeter. On these trucks, those connection posts are directly behind the dial notations for - and +.

I don't know about your '58 but I would have thought the wire from common starter lug to ammeter would have been connected to a post behind the 'charge' side of the meter. Even is connected backward it would only result in the ammeter reading backwards and shouldn't have resulted in chaos.

I agree with you, it was a slow short...a high resistance short. I'm not a expert but would think the area that caused the short would be the most black, burnt and fried..just like the weld pool of a MIG or stick welder, it's where the action was.

If the battery is the source of system power then current was flowing from battery, back up the system where it sound a path to ground. This path took it to the ammeter but not through the ammeter.

Stuart

Stuart,
My 59 is the opposite of what you described for the early trucks. The wiring diagram and harness instructions show the starter wire on the - D side and the other stuff going to the + C side of the gauge. I beleive it was working to the extent that it dropped down when I pulled the headlights on, but I never saw it go past the balance point into charge no matter what I did. If I turned off the headlights the gauge would go back into normal.

If the gauge could not handle the current on the starter wire side - D and it finally failed, it did so in spectacular fashion. If I had high resistance, high heat and it caused the failure, then I have to be able to find out why. Does not seem to me that too many things could cause it since it was a single fairly large wire connected only to the stomp starter top terminal and straight to the back of the ammeter. Terminal on the ammeter was good and supplied with the harness.

If the gauge is a non USA part and I bet it is, and it was a defective part, I am guessing someone else will see the same thing eventually.

As I worked on it today I saw that the stomp end of the wire under the battery cable was not affected in the same way. Looked fine and it was quite clear, as you said, that the grounding took place where it is really fried. It heated the copper up going back to the stomp and melted the tape and insulation, but the disaster end of this business was right at the ammeter. Ralph

Ralph,

Was there only one wire connected to the D side of the ammeter? I found a diagram for a '58 and it showed that terminal as a connection point for the power wire to the horn relay too.

I thought you had some horn relay questions earlier this week and wondered if there was a correlation. You have noted that the destruction stopped at the ammeter so this question has probably been answered.

Stuart

Interesting point Stuart as the horn relay was the only addition to the electricl system this week when I put the new wheel and horn push on and hooked up the relay. And the power for the horn relay comes via the voltage regulator from the + side of the ammeter. The ammeter has double spade terminals and on the + side ,one terminal feeds the voltage regulator (and ultimately the horn relay) and the other spade on that side feeds the headlight switch. All of that wiring was fine.

I gave that some consideration as it is the "last" thing I worked on before the meltdown but wonder why the other side of the ammeter would fry? The horn relay hooked right up and works fine but perhaps I created high resistance and it lead to failure on the - side?? Seems goofy though as the horn was not being pushed and was working fine. I do suscribe to the idea that the last thing I messed with is suspect but just can not see what I could have done. Ralph

I had a similar problem with my 57 chev. To make a long story short I fried the wire from the front right parking light to the switch. There seem to be no reason for this to happen. I replaced the switch and re wired the lights and preyed they now work with no problems. Why this happened is beyond me so maybe Stuart is right it was a freak thing. One explanation was there was short somewhere and it chose that wire to run all the way to the switch or the switch went bad... my 2 cents here ... Peter

I just read this post/thread. Thank you very much. I had this problem last weekend on my 55 2nd. Smoke under the dash. I pulled the battery wire. Then reached under the dash to find a cooked wire. I have not pulled out the instrument panel but believe it is the wire from the Ammeter to the ignition switch. There is another wire from that same post. I believe it goes from the ignition switch to the light switch for power.

From this thread I realize that the power coming into the ammeter is directly from the starter then runs on to the ignition switch.

This will help me next weekend when I get time to pull all of this apart to see what happened and do damage control.

Thanks again,

Dennis,
I will be interested in what you determine. I have not been able to rule out the ammeter doing the Crazy Ivan on me but it seems strange as it is designed to pass the current. If it wasn't for the fact that it took a couple of hours to happen I would not be so amazed. But the bubbling of the insulation plastic on the INSIDE of the case as well as the heat discolor of the rear of the case sure indicates that the heat from grounding was right at the case. I know I had no direct ground when I hooked the battery up as I always connect the positive last as Bill suggests and no hint of a spark. It must of been more of a steady draw building heat until the meltdown. I ordered another new ammeter and will try again but I am for sure gonna fuse. Ralph

Ralph,
This questioned my electrical ability and the equipment that is in my truck. I am using the original ignition & light switches. I do realize the I wired this truck about 8 years ago with a harness from one of the accepted vendors. I have been waiting for the slowest machine shop on the planet to finish my engine. I do not want to discuss that. Thank you very much.

But the problem was that with the key on - the engine started nicely and purred like a cat. Unfortunately, it would not turn off. I had to put my hand over the carburetor to kill the engine. So, I assumed their was a wiring problem or connection corrosion. I pulled down both switches and checked the wiring. While doing this I cleaned the terminals and put it back together.

After the smoke I think the wire from the ignition switch, and connected to the light switch, pulled out of the plastic protector and grounded on the dash. Somehow the wire from the ammeter to the ignition switch took the damage of frying. Now it is a bare wire with connectors on both ends.

Funny.

I will take the speedometer gauge panel off this coming weekend and see how the wiring is. I will post after I look into that.

Anyways. Before I decided to check the wiring there was no problem with fire, smoke, or anything. Just the engine would not shut off. What is up with that?

Thanks.

I would think that the ignition switch was removed from the circuit. When you turned the key off and the truck kept running, the switch was not doing what it was supposed to do. Then you got grounded out somewhere along that wire between the switch and the ammeter and that lead to the melting of the insulation on that wire as you describe. Perhaps not in that order but if you could not use the key to turn the truck off, it was out of order somehow. Ralph

The "run on" problem has been discussed before.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Board=2&Number=88201&Searchpage=1&Main=13310&Words=%26quot%3Bengine+will+continue+to+run%26quot%3B&topic=0&Search=true#Post88201

Hopefully this will help

It's Friday. That is cool. This weekend I will go back to tackling this electrical thingy.

I have been studying the wiring diagram.

Under the dash it looks like the wire comes into the ammeter then on to the ignition switch. The same post has a wire to the light switch for power. Both are hot all the time.

I also note that there is a post and wire to the distributor. Somehow the regulator and resistor is involved. I will try to follow the diagram with the wires to figure out if the ignition switch or light switch is involved with my problems.

Oh. Another wrench in the mess is the head lights. I got the briliant idea to go halegon. I bought the harness from one of the vendors and have it on the truck. Headlights don't work. I need to check to make sure the switch wires are in the equation for this. Unfortunately, the instructions were written by our Chinese brothers. The are in Chinese and translated in a quick-quick english jargon. Crappy but a start. I seem to think the light switch wires need to be connected to the circuits so that the relay switches get excited and open up to provide that added electricity for the halegon bulbs.

Where is Mr. Horvath when needed? I need to access his site to see if my wiring is good.

Thanks again to all for help and advice.

Oh. Waldo thank you for the link but I stayed with the generator and did not change to an alternator. Probably stupid of me but I will learn.