SN95 Alternator Wiring Harness Upgrade?

90lxwhite

I'm kind of a She-Man
5 Year Member
Aug 25, 2011
3,311
374
134
Between the Red and Rio
Noobster question here: So recently my alternator wiring harness(the 3 wires)shot its wad and I replaced it w a stock piece. My question is now that I'm running an msd box do I need one w thicker wire? The one that was fried was the original w over 300k mi on it so I guess it was due but does the msd box have any ill affects on it or can the stock 3G wire harness handle things just fine? Is there even a product out there? Ie plug and play harness w thicker wire.
 
Last edited:
  • Sponsors (?)


what alternator are you running. Hopefully not a 3g off off the stock 2g power wires. Any 3g/6g needs a minimum dedicated 4 gauge power directly to the starter solenoid with an inline 125 amp fuse. You can reuse the stock stator wire off the 2g harness but that's it. Also, an additional 4 gauge ground wire from the 2ndary ground point behind the battery and chassis is needed.

If you are still running the stock 2g alternator with the stock wiring, I would recommend swapping to a 3g. You have already witnessed why it is a fire hazard.
 
what alternator are you running. Hopefully not a 3g off off the stock 2g power wires. Any 3g/6g needs a minimum dedicated 4 gauge power directly to the starter solenoid with an inline 125 amp fuse. You can reuse the stock stator wire off the 2g harness but that's it. Also, an additional 4 gauge ground wire from the 2ndary ground point behind the battery and chassis is needed.

If you are still running the stock 2g alternator with the stock wiring, I would recommend swapping to a 3g. You have already witnessed why it is a fire hazard.
Nah man, this is a '95 that came stock w a 3G, this isn't an upgrade deal, y'all are upgrading to my chit.;) I was just wondering if I needed a wiring upgrade from there.
 
For piece of mind if you want to replace the wiring I'm sure you could. Fresh positive and beefier negative cable with an inline fuse. In all honesty I would have to wonder why your plug crapped out. You went through two alts in a very short amount of time. Maybe one kicked out more juice than it was supposed to abd the result was a toasted plug.
 
  • Like
Reactions: 1 user
For piece of mind if you want to replace the wiring I'm sure you could. Fresh positive and beefier negative cable with an inline fuse. In all honesty I would have to wonder why your plug crapped out. You went through two alts in a very short amount of time. Maybe one kicked out more juice than it was supposed to abd the result was a toasted plug.
Yeah man chicken or egg situation I guess. I'm not sure if the wires killed the alt or the alt killed the wires. The 1st alternator was the orinal with somewhere around 380k mi and the harness was original too. I replaced the former w a rebuilt motorcraft and reused the oem harness. Two days later the "new" one was bad. Finally figure out a direction to go in when just so happened to touch the alternator and it was hot and the car hadn't ran in like a day. I replaced alt and pig tail(i noticed the pig tail wires were all brittle.) and now it runs. When you say fresh + and bigger - are you referring to the battery cables? Just so I can learn something new today why a larger negative vs positive?
 
For piece of mind if you want to replace the wiring I'm sure you could. Fresh positive and beefier negative cable with an inline fuse. In all honesty I would have to wonder why your plug crapped out. You went through two alts in a very short amount of time. Maybe one kicked out more juice than it was supposed to abd the result was a toasted plug.

All it take to overheat the wiring and connections is some extra resistance and a high current draw. The connection or wire with the higher than stock resistance creates heat, which creates more resistance, on and on, it's a vicious circle. What happens then is that the wire or connection finally fails, sometimes in fire or if you are lucky, it just quits working.

A voltmeter is handy if you are familiar with how to use it to find bad connections. Measure the voltage drop across a connection while trying to start the car: more than .1 volts across a connection indicates a problem. The voltage drop tests need to be done while maximum load is on the circuit under test. It's the current flowing through a connection or wire that causes the voltage drop.

See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .

attachment.php


Voltage drops should not exceed the following:
200 mV Wire or cable
300 mV Switch or solenoid
100 mV Ground
0.0V Connections
A voltage drop lower that spec is always acceptable.
 
All it take to overheat the wiring and connections is some extra resistance and a high current draw. The connection or wire with the higher than stock resistance creates heat, which creates more resistance, on and on, it's a vicious circle. What happens then is that the wire or connection finally fails, sometimes in fire or if you are lucky, it just quits working.

A voltmeter is handy if you are familiar with how to use it to find bad connections. Measure the voltage drop across a connection while trying to start the car: more than .1 volts across a connection indicates a problem. The voltage drop tests need to be done while maximum load is on the circuit under test. It's the current flowing through a connection or wire that causes the voltage drop.

See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .

attachment.php


Voltage drops should not exceed the following:
200 mV Wire or cable
300 mV Switch or solenoid
100 mV Ground
0.0V Connections
A voltage drop lower that spec is always acceptable.
Fn electricity man..