Charging system problem

[packin45]

Mini max shows 14.5 volts at idle, but while driving that will go up to 16 and I get all sort of messages on the dash, at times it will go as high as 17.5 and everything will shut down completely I assume it's over voltage protected.

I had our shop mechanic hook it up to a scanner and he said he has had 2 trucks with the same codes and same issues and they ended up being a broken control wire from alternator to somewhere over by PCM or the PCM itself. I believe it's the red wire in the 3 wire connection at the alternator. Any help would be greatly appreciated.


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[sootie]

Could also simply be a bad alternator

 

[packin45]

Is there any way I can determine it's the alternator? I hate to throw an alternator at it only it find out a 6' run of wire would have solved the problem.

Also I have started the truck around 50 times since this started. No hiccups starting the truck


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[bfuller83]

You can meter the ohms on the wire with a mulitimeter. Just Go To The CONNECTOR And Find A Place To Break Into The wire.

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[BigRed97]

Overlay the 2 wires (red and yellow if I remember right) from the pcm to the alternator, and drive it, if the problem goes away it's the wiring, if it doesn't it's the alternator

 

[BigRed97]

You can meter the ohms on the wire with a mulitimeter. Just Go To The CONNECTOR And Find A Place To Break Into The wire.

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And don't do that. Do it right with the proper probe

 

[packin45]

Yellow wire checks out. Red wire should be hot and it isn't. Pulling my hair out trying to ding the other end. Wiring diagram says it goes to a fusible link. But those are all large gauge wire. I have yet to find a small red wire. Can I feed that red wire 12v?


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[BigRed97]

It's tied in to the fusible link with another large gauge wire. It's there just need to dig a little
Probably 8 inches down from the stud where the large gauge wire connects

Do not feed any wire straight unprotected voltage

 

[BigRed97]

these might help
in the second picture, the fuse link splices are identified in red(lower left corner)