charging system

[Hahndol]

Hi, I have a custom sand rail and the charging wire from the alternator is getting very hot and eventually blows the inline fuse. I've replaced the the neg and positive battery cables. Bypassed to fuse block. Replaced the ignition switch and push button starter. The alternator is new. The starter is new as well. The battery voltage will the motor is idling is around 13.8 vdc. Its not over charging. It seems like there is a short but I don't know where else to check. Any ideas?

[Dale M.]

[Hahndol]

The voltage after I disconnect the alternator goes up to 14.5 vdc to 14.8 vdc at the alternator post.

The battery doesn't charge after I disconnect the wire. It starts to discharge.

The old alternator was charging but not great I thought that there could have been a problem with the voltage regulator. I was running out of options. So, I decided to replace the alternator.

The wire is 12 gauge with a 30amp inline fuse.

[Dale M.]

Umm... #12 gauge wire is kind of small, should be more like a #8 or #10.... And a 30 amp fuse is kind of small if it is really a alternator. Most alternators are capable of about 55 amp outputs...

You mentioned a "regulator" you sure you have alternator (there was only 1 year that used alternator with external regulator), all later alternators only have B+ lead to battery for charging and D+ to ALT/GEN light...
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[Hahndol]

I'll switch the wire and fuse block to 10 gauge. I've never had a problem before.

Yes, this is an alternator. It has has an internal voltage regulator. Its a 75 amp out put.

The only draw on the alternator/battery is the ignition system. I've taken the lights and all of the gauges out of the system. There should be very little amp draw but the charging wire is getting hot to the touch.

[Dale M.]

[Hahndol]

The battery is brand new. I'm leaning towards a short in the electrical system. But, I've gone through everything. Running out of ideas.

[Wulfthang]

Electrical problems can be difficult to diagnose because you can't "see" the problem like a hole in a piston or a bent rod. First, fix the problems you know about and then test for the ones you don't know about.

Pull the alternator and battery and have them both tested. "New" can still be defective.

The alternator sounds like a "one wire" unit. Did the car have that kind of alternator to start with or is it a conversion? Sometimes, that kind of conversion requires a kit to make it work. I had to get a plug in regulator conversion to make mine work. (Ford 135 amp)

Absolutely replace the 12 gauge feed wire for the alternator. A 12 gauge wire is rated 20 amps max. It may be ok if the battery is fully charged and there's no drain like headlights, etc. but a couple of starts and stop and go traffic will discharge the battery. Then the alternator will charge at a higher rate and the 12 gauge wire will overheat and melt. It should be 6 gauge minimum. 4 gauge is better. You can get 100 amp fuse blocks on Fleabay for under 10 bucks.

If you had a short in the system, it would have to be only a partial short. A true short circuit would burn the wiring and/or blow the fuses. Feel the fuse block and wiring harness. Any hot spots? No hot spots then probably no partial short.

Honestly, what you're describing....."charging wire from the alternator is getting very hot and eventually blows the inline fuse"....... combined with .........."The wire is 12 gauge with a 30amp inline fuse"......sounds like it's under-wired and under-fused. Replace it with a larger wire and fuse.

[liquidrush]

Can you post some pics of your setup? Might be helpful. On mine I ran the charge wire to the B+ on the starter and that cable goes to the battery + terminal. It's 10ga wire too and all of my wire ends are soldered, no crimps. Make sure those connections are clean and tight meaning disconnect them, clean the terminals and reassemble them and if any of your wires are crimped check them carefully and I'd solder them. Make sure you have a solid ground from the battery to the block and again, take them apart, clean and reassemble. I also got rid of every incandescent bulb on it and replaced them with LEDs, much less current draw.Trust nothing, verify everything.

[Aerindel]

[stevebaz]

check the battery connections and the wire up to the starter. everything want to connect at the starter. if the wires and connection then power is going to draw from someplace else. I am surprised you could draw everything through a 12 gauge wire at the alternator. grounds are just as important as positive wiring.