Voltage gauge low and CEL but alt tested fine?

[powerstroker66]

Showing about 10v on the gauge in the cab with a CEL on but when i go to the alternator i have 14.4v off the back, at the GP relay, batteries, etc No battery light on and my scanner wont read the code nor will the truck start with the scanner plugged in but fires right up when i unplug it. Also, the alternator gets pretty toasty. Any ideas!? thanks!

 

[Arisley]

Number one, you cannot trust the gauge in the cab. Check the connection on the back of the alternator, that connector can get corroded on the inside of it, under the heat shrink. Check battery connections. Make sure the connections there have no corrosion. Check and make sure grounds are clean and tight.

 

[powerstroker66]

What exactly does the volt meter in the cab pull from? I have an airbag light on too..

 

[mandkole]

When you dealt with that fuel pump issue and the relay box, did the replacement come from the same truck? Since those issues were not reported present before, Id go back and check your work from the earlier repairs.

 

[powerstroker66]

The engine, trans, pcm, and main harness are all from the same truck. Im going to ohm out all grounds and cllean the main lead from the alt going into the fuse block. Weird part is it will not scan and when i tried to scan it, the truck shut off..