The Stovebolt Site Forums The Shop Area The Electrical Bay Positive battery cable hot

Hey guys,

I went out to start my truck [57 3100 with a '78 small block] and after finally getting it to start [maybe a minute or so of On and Off on the started button] that the battery disconnect spun off in my hand. The disconnect was so hot the know had melted from the bolt, the bolt was too warm to hold and the cable itself was very warm.

Here is the style of disconnect that is on the truck http://www.summitracing.com/parts/SUM-G1439/

Any ideas what is going on? The truck has a starter button mounted in the dash that engages the starter, and without the key cylinder in On, the truck would only turn over but will not start.

I have been suspecting for some time my alternator is going bad as the truck cranks well the first 5-10 seconds but then always seems to loose power. Maybe this hot wire is the illustration of a different problem?

did you install that thing or was it there when you got the truck?
are you sure it's making 100% good contact when "on"?
it could definitely cause the battery to run down fast and poor connections will heat things up fast, but why does the engine take more than a couple seconds to start? a small block in good tune should start in a couple revolutions, although maybe you don't pump the gas at all before hitting the switch?

of course it could be a bum starter that's drawing too much juice too, but you need to make sure all the wiring is 100% and it's properly tuned - I'd start with scrapping the low tech disconnect, or at least bypassing it for the time being - also get the battery checked for weak cells

Bill

Look at the capacity specification on the disconnect- - - - -"100 continuous amp rating". You're sending a boy to do a man's job. Take that thing off and throw it as far as you can, and get a disconnector that's able to handle enough current. I've seen current flow of 250 amps or more on a hot restart, or when cranking a very cold engine. For a good safety margin, try to find a disconnector with at least a 500 amp rating. All the connections need to be very clean and tight, and you need to find out why it's not starting within 3 to 5 seconds, maximum.

A starter has a maximum run time of about 20 seconds, after which it needs a 20-minute cooldown. after another run time of 20 seconds, there needs to be a 2-hour cooldown. That's Delco factory bulletin information- - - -I've taught their electrical courses for 30+ years. Repeatedly running the starter for long periods overheats the windings, and can do permanent damage to the starter, since it's designed to run in an extreme overload for a few seconds, and have a long cool-down period between uses.

Jerry

Bill- Sorry I should have mentioned that the switch was there when I bought the truck ~ about 10 years ago now. As for the hard starting, that is a result of my rebuilding and tossing on the truck yesterday and runs fine once warm, but obviously needs some adjustment/ tuning for cold starting! Battery is only a year old and was not an issue last year, but again had this quick drain on cold restarts [hence my rebuild where I found melted components from the ethanol.:- ( ]

Jerry- Thanks for the advise. I am not sure why the switch was there to start with unless there was a concern with theft. To be honest I have never left the thing connected so maybe it was a quick fix for a short. It is gone tomorrow and if the battery is dead then I will have some testing to do!

Out of curiosity what gauge cable should be running to the starter?

There is no such thing as a too-big battery cable. A 12 volt system can get by with a #4 cable, but it will have a lot less voltage drop with a big one, #1 or #0. On the race cars, we made our own cables out of #0 welder cable with about a thousand hair-fine strands of wire, and soldered all the connections. They would crank a 12:1 compression engine easily, and I've seen surge current of close to 1,000 amps when a high-torque starter kicked in on a hot restart.
Jerry

You guys were right the switch was the problem. I pulled it off, connected the positive cable directly to the post as was surprised how much 'stronger' or maybe faster and louder it cranked. I am not sure the reason of the switch so I am gonna let it sit for a couple days and see if there is a drain it was intended to stop.

As for the cable, there are no markings, but it is the same O.D. as an orange 16/3 extension cord I have in the garage. Guessing I am on the low end of the acceptable size?

And I hooked the manual choke up and the truck started right up!

yes, that'd be the minimal-sized cable for modern 12V cars - will work as long as everything is 100%, but wouldn't hurt to find a heavier one, especially if the one you've got has the bolt on ends, get one with sealed molded on ends which won't corrode as much

Bill

If it is size on an extension cord I think it may be around #4 or 6 conductor. As Jerry said I would have nothing less than #0 and preferably 2/0.

What I have found works well is welding cable ie type SO - IF you can use lugs to terminate them on battery. Otherwise stuck with premade with connections. Oversize on electrical is a good (cool) thing. Cool is the challenge on electrical keep it cool and all is OK.

You may be able to visit a welding shop or weld equip repair shop and get some scrap pieces of weld cable.

Another option is to check out the farm store tractor department. Don't look in the automotive areas, they only have the standard 4 gauge. But in the tractor parts area, you can find 0 and 00 cables already made up, mainly for Deisel tractor use. Around here, they actually are around the same price as the smaller cables.
Autozone also carries some heavier cables, mainly 2 gauge, mostly for the kiddies with the big stereos. I ran one of these on my S10 when the ground cable went sour.