The Stovebolt Site Forums The Shop Area The Electrical Bay Starter to ammeter meltdown. Fuse? 59 3100 6 Cyl

After my meltdown of the wire going from my stomp style starter to the ammeter I wrote another thread about, I have decided to fuse that line. I hate the smell of that burning insulation!

The brand new original style replacement wiring harness of course does not use any fuse, but I am going to put one in. What AMP in line fuse would you recommend for that wire between the starter and running under the dash to the ammeter? Tha is the one that dead shorted at the ammeter somehow and seems like a good idea to fuse.

I am hopeful that it was a fluke thing where the new connection popped off and/or grounded out at the ammeter as that is where the meltdown was the worse. I bought a new ammeter and will install that along with the new in line fuse, probably under the dash but want to get the amp rating right. Thoughts? Thanks Ralph

I wouldn't put a fuse in there, and the engineers at GM obviously agreed. If anything were to go wrong with that fuse, you could be heading down the highway with no power, and no lights!

I don't know why your main lead to the ammeter got hot, maybe a defective ammeter or not installed right (?) but I'd venture to say that 99% of the trucks around here are wired as factory, right to the ammeter. Just use extreme care with that lead, it should go through a rubber grommet to get inside the cab, then I'd use a soldered connection and make sure it's clean and tight.

Waldo53,
I agreed with you when I put the new harness in and the new ammeter and I used the correct connection. But one thing is certain, that ammeter (and of course the new one is an exact replacement as they are all from one place) grounded out and caused quite a meltdown of surrounding insulation and other wires touching it as it is a pretty heavy wire.

I am sure it would have cause a fire as the wire was red hot and started to cook thru the firewall pad etc when I saw the smoke in the driveway. I want to think it was my fault as opposed to the "new" ammeter failing but it happened after the truck was off for over 30 minutes. I did not have the speedo cable hooked up on the back of the instument panel and want to think the metal cable must of made contact with the post on the ammeter but it sure does not look like it.

I have double checked the harness and everything else looks correct. I just hate the thought that I have a slow cook going on that wire due to something I have fouled up and not have it fused. I also am not convinced that this replacement ammeter is of the same quality that a GM engineer had in mind. My guess is this comes from ASIA like a lot of the parts we can afford to get and will not be produced here.

If I knew what I was doing, I would leave the new gauge in for original appearance and hook in a quality small volt/amp type gauge. The fuse seems like a safe way to at least see if I have a repeat smoke check.

Thanks Ralph

why wire an ammeter at all.
keep the real high amperage stuff OUT of the cab altogether. use relays were you can and a volt meter.
stock is stock but a safer way IS better.
my .02 it's your truck.
' Amperage is a measure of current flow, and ALL of the current used to the vehicle as well as recharge the battery was routed through this one gauge–which caused the gauge to display the battery charge rate. Both the alternator and the battery were mounted up front passenger side, oppisite, under the floor. And the AMP gauge was at the dash. It was an arrangement resulting with a very long wire circuit charging the battery.
http://www.madelectrical.com/electricaltech/amp-gauges.shtml

You note that your speedo drive was unhooked behind the dash. It is entirely possible that the speedo cable, while spinning, took off the insulation to your wiring and caued a dead short to the transmission or firewall. Ask me how I know. I let the smoke out of the pink wire behind the dash of my '61 in exactly that way. Perhaps a re-look at the proximity of the speedo cable to the affected area on the wire might show this to be possible in your situation. And then you might rule out the gauge and simply rewire again as the factory did. Inline fuse on starter circuit=bad idea

It is not unusual for the amp gauge to ground out after the cheap insulation around it gives way. I've had that happen several times on a tractor, in fact I'll be picking up a replacement tomorrow.

Pretty good article on the madelectrical site, but it was misquoted above. The actual quote is: "amperage is a measure of current flow, and all of the current used to recharge the battery was routed through this guage.....". The main point of the article was the problem of inadequate bulkhead connectors on the early Mopars.

The amp guage merely shows current into, or out of, the battery. Nothing more. (check the wiring diagram in the article)
A common misconception is that ALL the current your rig is using runs through the ammeter. Not true. I can be running with my lights on high beam, heater blasting, wipers cranking, and still show "0" or neutral on the ammeter. The load is being supplied by the alt/gen independent of the ammeter.

Hey, I have no problem with relays, breakers, or whatever if that's what you want to do. All's I'm saying is that the GM engineers of the day designed our old trucks this way, and I've been around them all my life and haven't seen an ammeter or any associated wiring catch on fire yet.

And the "real high amperage stuff" i.e. the starter motor, IS out of the cab.

To get back to the original thought about a fuse, what kind of amps does the ammeter from starter wire carry IF I was going to fuse it. Seems like it is a 12 gauge wire or so. Would a 25 amp fuse be good? Thanks for the input.

Ralph

you'd hafta fuse it to take the full output of your generator/alternator

Bill

How many amps are the original ammeters rated for ?
Art Deco ?
Advance Design ?
Task Force ?

A stock generator puts out 30-35 amps and alternators are higher. The load actually put on your wire feed also depends on your accessories, and total amperage usage. I think the fuse idea is a bad idea. A 12 guage wire isn't anywhere near big enough anyhow. I would use a #8 at a minumum.

Whitedog,
The replacement wire harness has the same size wire as the original GM engineer designed harness for the generator/ammeter setup. Do you think the use of the bigger #8 wire would somehow help? I think it is a 12 ga wire now. Thanks Ralph

no, heavier wire wouldn't help, just take longer to destroy more things if you get a dead short someplace .... wire it right and go with factory, your meltdown wasn't because of the design of the system, nor is it likely to re-occur unless you do something wrong - was it your replacement gauge? something routed wrong and touching something? improper connections? fuseing the main supply will just leave you in the dark at the side of the road someday, everything should have it's own protection

Bill

I had the same problem once; it was the speedometer cable shorting to the ammeter lead. Once I resolved that, no more problems with the original wiring.

After you find the reason for the shorting you could always use a self resetting circuit breaker - about $5 from any FLAPS, Boating outfitter, farm store, etc.

Or you could use fusible link available at any automotive store. It is a lead/tin based wire intended to burn out like a fuse. All Domestic automakers use this on all leads from the power tap to the fuse block on all vehicles from the mid 70's on. It is intended to blow at a higher value than the fuse, however it is intended to prevent fires (and have the service department charge you $2500 for a new harness vs $1 worth of fusible link)

However the original idea of running all the system current thru an ammeter worked well when the total system load was about 10 amps, however with a power plant swap, alternator swap, etc. the original wiring may soon be taxed. I myself am going with a simple volt meter.

For example todays cars 150 amp alternators, defrosters, heated seats, gazillion watt stereos, xenon headlamps, etc. the load center on todays cars is connected to the battery with a 4 gauge wire, sometimes with a 120 amp fuse, or more commonly with a splice and 10-20 circuits of fusible link.

I have had amp meters fail before. They can make a mess of things to say the least. As for me I would put back in an amp meter and not a fuse. If you feel the need to install a fuse you should use a fuse link wire and not a glass or plastic fuse. You will need at least 40 amp wire but I would use a 50. The reason for the fuse link wire is that it is not a quick blow fuse and can take a lot of surge before it will burn into.

I double checked the new harness and installed a brand new reproduction ammeter after running a new starter to ammeter wire. This time I made certain the speedo cable was connected in case that was the culprit. All connections were checked and wire locations were okay.

One difference I noticed right away after the 235 started up is the lack of any movement at all in the ammeter gauge, even when I pull the headlights on or push up the throttle a bit. It sits dead center and does not flicker. The generator supports nothing extra as the heater is not in and there is no radio. As the ammeter only shows current passing through,and it is not showing discharge do you think the lack of any movement is normal? Before the ground out of the other one, I noticed movement when I pulled the headlights on. Does the voltage regulator and generator have a simple test to insure they are up to speed and working correctly?

One of the reasons I love these old trucks is the basic simplicity of the systems. Of course the wiring/electrical intimidates me the most and is the only issue I am having during this restoration of this 59. Thanks for your input

If you turn off the engine and operate the lights and heater does the meter show discharge? If knot then it may not be connected properly. When hooked up properly the only electrical currant not hooked to the amp meter is the big battery cable going to the starter motor. Everything else should pass through the amp meter.

Okay....I was wrong about the connections. I had one of the three ammeter connections on the wrong spade terminal. After looking at the wiring diagram long enough I realized the wire from the voltage regulator to the charge side of the ammeter was on the discharge side; thus no indication of charging. Hooked it all back up and now the ammeter shows discharge when the lights are on. Still can not get the ammeter to show charging so tomorrow I am going to troubleshoot the generator/voltage regulator.

You may not have a problem with charge if your battery is hot. Turn on your headlamps and walk away for 20-30 min., then return and start the truck. Is it charging now? If so its a fix, if not, then you need to test the charging system.