Alternator Not Charging

[Fri Guy]

Was working on my car today. Alternator seemed fine. Disconnected the battery while doing some stuff on it. When I reconnected it the negative post arched pretty good but car started and moved it out the garage. When it was time to move it back into the garage I noticed the battery light blinking. Battery is relocated to the rear. I checked the voltage with car running and it wasn’t charging.

I’m running a 4 gauge cable with a little fuse mega 200A from the starter solenoid to the alternator. I checked the 4 gauge post on the back of the alternator with key off and not getting power. I’m getting power at the solenoid. Checked one terminal on the mega fuse and had power. Checked the other side of terminal an no power.

Should I be getting power on both terminals of the mega fuse? This is all with a fully charged battery and key off.

 

[Noobz347]

A couple of things come to mind:

The arch when you went to reconnect the battery: A small arch is OK. A healthy one usually indicates that the diode in the alternator is bad. By hooking the terminal back up, you're essentially, trying to 'motor' the alternator. So, I would have that looked at.

If the above is true, then you could very well have blown the fuse.

With the battery disconnected and the engine off, you can test continuity of the fuse.

 

[Fri Guy]

I tested the fuse and it was bad. Bought a new one and tested it prior to installing and tested good. Installed it and reconnected the battery and I got the same arching when attaching the negative cable. Looks like it blew the fuse again. Removed the fuse to test it and it’s bad. Battery voltage when disconnected is 12.4 volts. Not sure why it would be arching and blowing the fuse. Any advice?

 

[Noobz347]

I tested the fuse and it was bad. Bought a new one and tested it prior to installing and tested good. Installed it and reconnected the battery and I got the same arching when attaching the negative cable. Looks like it blew the fuse again. Removed the fuse to test it and it’s bad. Battery voltage when disconnected is 12.4 volts. Not sure why it would be arching and blowing the fuse. Any advice?

Are you familiar with how a multi-meter works and how to use it?

If so, start looking for the [short to ground] that you are now getting that is killing the fuse.

Examine wiring in any areas that you have recently performed maintenance. Do your tests with and without the alternator connected to the harness. When you get to a point where you disconnect the alternator, remove the thing and take it to the parts store to be tested.

If however, the things that I've posted here sound like Greek to you, then you need to get some help.

 

[Fri Guy]

I’m not that great with a meter. The only thing I did yesterday was add some refrigerant to see if my compressor would turn on. I also siphoned out the fluid from the power steering pump and added new type F. I did spill a little on a ground cable that attaches from the frame to engine block. But don’t think that would cause anything.

 

[AeroCoupe]

If you have a DVM set it to the continuity setting.

Touch the red and back leads together and you should get a tone.

I am assuming you have the fuse between the battery and the starter solenoid that is mounted on the driver side inner fender. Disconnect that wire from the starter solenoid. Put the black lead of the DVM on a good ground and the red lead on the end of the wire from the battery. If you get a tone then you have a dead short to ground on that wire.

Rinse and repeat for any other wires (starter and alternator).

 

[Fri Guy]

I ended up removing the alternator to have it tested. It tested good at two different locations. So with the alternator off the car I put a new fuse in and connected the battery. No big arching. Fuse did not blow. With the alternator still not attached to the car I connected the 4 gauge power wire and reconnected the battery and no arching.

One thing I did notice prior to removing the alternator off the car was with the front of the car jacked up and the tires off the ground, the front sway bar was touching the insulation of the ring terminal on the 4 gauge power wire. That insulation looked like it had a little missing spot on it. Sway bar might have been touching the alternator case as well. But I’m assuming with the car on the ground and the tires tucked back up that the seat bar isn’t near the alternator. I placed a jack under the tire and jacked it up to confirm that.

Alternator is relocated to the bottom due to the Vortech supercharger. I wrapped some electrical tape over the terminal insulation and reinstalled everything. This time I mounted the power wire in a different position than before. Got the car back on the ground and gave it a try. Everything functioned as normal. No blown fuse and alternator charging as normal.

So I honestly don’t have any real idea what happened. I checked over the rest of the wiring and all looked good.

 

[AeroCoupe]

You know what happened. The sway bar was grounding out on the lug. If you can get a mirror down there when its on the ground and the suspension loaded my bet is it was barely touching and over time it wore a hole in it.