John deere 6920S Alternator warning

[Laser]

Hi

I hope there are some JD experts on here.

I have a John deere 04 6920S that throws up an alternator warning on the dash every now and then.
Sometimes it comes on every few minutes and sometimes its can say off for over 20mins.
It can stay on for over a minute, and other times it only comes on for a second and off again.
Battery light and warning symbol illuminate and error message "Alternator Error" on dash
Buzzer also comes on every time which is quite irritating.

Getting 14.4 V when tractor is running and doesn't change when warning is on the dash.
I had alternator sent off for refurb anyway and fitted last week but issue still persists.

I assume is some wiring or communication issues, as battery and alternator are fine.

Any ideas where to start?

 

[Kevtherev]

Could be clutch on alternator pulley had similar on 20 series.

 

[Laser]

Could be clutch on alternator pulley had similar on 20 series.

Thanks for the reply
Clutch was changed when alternator was refurbished.
So I think I can rule that one out.

 

[Tractor Tim]

Ours does the same 04 reg as well been to JD a few times for unrelated things and asked them to check it they can never find anything wrong with it possibly a bad connection been going on a few years now and hasn't developed into anything worse

 

[acorn]

....from previous experience......check and clean the earth strap bolted to the cylinder head....

 

[freelancer]

Had the same in our JD 6506.... In the end there was "connection" between the both start assist terminals under the right door!

 

[Combine Rescue]

Compare voltage on battery and D+ terminal.
Bad joints can give the light comes up.
However I have had repaired does dashboards before for with this problem

 

[Gerbert]

Have had it for two years on my 04 6420, keep meaning to look at it but other then the light there is no problem.

 

[marco]

Had it on a 6820, turned out to be the dash. Check all body earth's first and wiring harness at back right pillar of the cab.

 

[Laser]

Thanks for all the replies.
Will clean all body earths at the weekend and see how that goes. Will also check pillar wiring, but I would assume a fuse would blow if there was a wire stripped there?
@marco
Is a dash just a straight swap or is there some coding to be done?
@Tractor Tim
Does the buzzer not drive you mad going off every couple of minutes?

 

[Combine Rescue]

As long the dash has the same part no you should be OK. There are some parameter can be change but you can do without laptop.

 

[marco]

Thanks for all the replies.
Will clean all body earths at the weekend and see how that goes. Will also check pillar wiring, but I would assume a fuse would blow if there was a wire stripped there?
@marco
Is a dash just a straight swap or is there some coding to be done?
@Tractor Tim
Does the buzzer not drive you mad going off every couple of minutes?

The main dealer did it for us afew years ago. Local garage couldn't get to the bottom of it, main dealer swapped out with a tractor in stock to see if it cured it, then replaced with new.

 

[marshbarn]

 

[Laser]

De-beep might be an option

Marco, how much was a new dash from the dealers?

 

[marco]

De-beep might be an option

Marco, how much was a new dash from the dealers?

I think it was somewhere around 1800€ fitted.

 

[flyonthewall]

We had exactly the same problem ended up replacing the alternator unnecessarily. Turned out to be the two big main maxi fuse holders, on the positive side of the battery were arching, cut out replace, 10 minute job. Dealer had in stock. More of a problem when lights on as I presume the load on alternator is greater. Occasionally the alternator light still comes on. Might be worth checking the earth leads still, unbolt and rub down with wet and dry. Start with the cheap easy solution!

 

[Laser]

Quick update,
Think I have solved this issue.
Cleaned the body earth and the legs of the two big fuses over the battery with some Emery cloth and haven’t had the issue for the past few weeks.
The body earth didn’t look bad to be honest, but the fuses were dirty and slightly corroded, so I would say the fuses were the most likely culprit.
No more annoying beep
thanks for the help