A while back my truck caught fire, and burnt some wires so I fixed all that I saw was bad but after that when the truck was running I would take the ground cable off and just touch it to the terminal what would result is a bright hot spark but terminals or cables never got hot so I didn't worry about it. Then the other day I noticed the lights getting dimmer and brighter so I thought my alternator was on the blitz. But I'm the kinda person who doesn't fix things untill I have trouble with it. Needless to say the other day my battery ran dead on me so I checked in to it. The cable end on the big wire to the alternator was burnt off from getting so hot. (this is the one that bolts onto the back of the alt.) so I put a new end on it and charged the battery and started my truck without the cable on the alternator. when I touch this cable to the spot where it goes on the alternator it sparks bad and if I hold it on there it gets hot so something is not right somewhere. any ideas? I tried a different alternator right after the fire when the battery terminal would spark but it didn't help with that problem. so I don't know if I switched the alternator if that would help. Another thing I tried switching the harness to the alternator and regulator and solenoid. but the truck I took it off of is different and now I have no power to nothing the differences are that my truck has an extra 4 prong plug and the new harness does not. but the alternator end of the harness is exactly the same. Please help me I needed to use my truck today and now I can't.

 

The is one of the common misconceptions that people have.

Disconnecting a battery cable with the engine running.

Never disconnect a battery cable while the engine is running, on an Alternator Charging System.

This particular practice came about in the 50's & early 60's when on a [size=3=]GENERATOR [/size] charging system they needed to Spike it, to start charging.

 

You probably need another Alternator & Voltage Regulator now.

 

why does this hurt them?

 

Because this SPIKE of current is harmful to the Diodes & Circuitry.

Alternator's work differently than Generator's


Maybe do a search in the electrical forum

 

The spike is called a "load dump transient" and puts voltages as high as 400V+ on your electrical system. This spike can and will blow the diodes in your alternator , destroy your regulator, and even knock out your radio and other devices.

A loose battery cable or poor connection can cause the same thing.