Case IH Steiger 715 Quadtrac unstable voltage

[pecanpie]

I got a Case IH 715 Quadtrac and the voltage has been unstable. it's confusing, sometimes goes down to 12v but then it can go back to around 14v.
I checked, when the display and also battery post are testing 12v the alternator says 14v, so I guess the alternator is okay. I've cleaned all the grounds and main strap ground from the engine to frame, but it's still the same.
Also when the voltage is reading low, like 12v when I turn all the lights on, it drops to around 11volts but it only drops .2voltage when the display is 14volts or more
Has anyone had the same issue before? can someone give me advice to fix this? thanks

 

[redm4chineguy]

Had a similar issue once, my alternator was working just fine but I was experiencing a voltage drop in the cab feed. Be sure to check the connectors and harness grounds, they can corrode in ways you might not see.

 

[Cranb3rry]

@pecanpie have you checked the battery? usually this kind of issue is because of a bad battery or loose electrical connections
Inspect all battery and alternator connections for tightness and corrosion
then, with the engine running, test the charging system, check if the voltage rises above the battery's static voltage