Deere 6620 combine - electrical demand on alternater

On my John Deere 6620 combine I see the electrical gauge drop and drop the more the electrical demand increases. I believe the gauge displays voltage rather than amperage. With no load and the engine running at high idle the needle can be straight up and down in the black zone of the gauge - pretty much the center of the gauge. Probably shows around 12 volts.

Then turn on the fan and air conditioner clutch and the needle drops in to the lower center, below the black, to the lower green, near the orange/red zone. I am also running an Ag Leader yield/moisture monitor. I should also mention that this combine is a sidehill which takes electricity also. All of these thing might drag the voltage closer to 10 volts.

By the time it starts to get dark and the lights come on the gauge is in the orange/red zone. I noticed last night the sidehill wasn't leveling. Take something off of the electrical load and it would level.

I noticed that I am starting to push trash at the cutter bar. Can low voltage affect the automatic header height?????? Combine is dial-a-matic. Platform is three wire. The head and combine are hooked up with the Deere adaptor wire. Yield monitor this afternoon wasn't accurate like it had been. Shut it down to clean bean dust and it wouldn't start without charging the battery. That only happened once in a week. When the lights are on they seem to stay bright, but the gauge is way low. Battery year is 2013. Is the alternator going south??? With all of this demand should the alternator keep up??? Is there an alternator that is an upgrade or is the OEM alternator OK? Thanks. Andy

For starters you are more likely running in the 14 volt category. Most alternators put out 16 volts. If it truely is at 12
volts at high idle your alternator is out.

If you are running Ag Leader you can get a digital readout on voltage. At least the two I have had through the years had that
option. Mess a bit with your display and you should be able to display voltage in a digital format.

Measured at the battery,at high Idle, the voltage should be 14.2 to 14.6 with a fully charged battery. Less means a slipping belt, or a faulty charging system.
Jim

Your alternator is shot. The bean dust and moisture more than likely did it in. I rarely get more than a year or so out of an alternator on the JD 6620s. Heavy load and terrible operating environment. IF you replace it or have it rebuilt, make sure it is the correct amperage. The combines use a higher amperage on than most of the tractors. The correct one will keep up with the draw of all the systems.

The automatic header is voltage sensitive because the solenoid coils have to activate the hydraulic valves. With low voltage they will not be strong enough to do that. This is also why your side hill did not level.

Now STOP running the machine with the bad alternator!!!!!!!! The lower voltage drives UP the amperage required to make things work. You can damage the solenoids and or coils in the side hill leveling system and the automatic header control. They get much hotter with low voltage.

Belt tight enough???

Yeh..it's volt-meter...I would check battery voltage with a digital voltmeter when it's not running to establish a baseline voltage for the batteries... then check it running...then check it with everything on and running(lights/ac/header clutch/etc)...the alternator should stay ahead of the baseline voltage with everything running

along that line.. maybe what is on there now was replaced with a unit that is too small in the past?

i could see that if its a Delco as they all "look alike".

but i'd agree. either the one you have is going bad, is the wrong one for your combine and/or your battery(ies) are on the week side too.