JD 710D electrical issues

[dbs]

My 710D has 6000 hr. For the past several months the warning light that the alternator is not working comes on and off periodically for no apparent reason. There is no power to all lights, wipers, and heater fan all the time. The batteries stay fully charged. I have changed out the alternator and ignition switch with no change to the condition. The dash warning lights all work. Fuses are all good. Anyone had a similar problem. Otherwise the machine starts and runs perfectly. Thanks

 

[Delmer]

Your accessories are a separate issue, maybe the accessory relay? they'd work until the battery was dead whether the alternator was charging or not. As far as I know (based on other deeres) there's nothing special about this system, you have a warning light in the line from the ignition switch feeding "excite" power to the alternator just like millions? of other alternator warning lights for decades.

Is the timing of the light coming on and off random, or is there any pattern? like does it come on for 5 minutes, off for 10? on for 1-10 seconds every now and then? I think I'd check all the connections, big alternator wire, battery cables, wiring harness grounds, also look for chafed bare spots on the cables, and maybe hook up a test lead at the alternator and run to a multimeter in the cab to see what the voltage does when the light comes on.

 

[dbs]

The turning on of the alternator light seems to be totally random. I have cleaned all the connections to the batteries, alternator and starter. The wiring harness from the starter hot lead to the fuse box seems to be unremarkable although difficult to examine due to due running through the center of the machine. It is also very dirty due to oil and dirt. I have read that oil can cause electrical problems is that your understanding as I had not heard of that before. I have read on this forum of a fellow with a JD 310D who had electrical problems due to rust in the floor of the machine impinging on the wire harness coming through the floor. He fixed it by running a separate wire and acting as a jumper wire through the floor. Apparently it was a large wire bringing power to the fuse box. Thanks for all the suggestions.

 

[JL Sargent]

There is a terminal on your alternator marked "W". When the engine is running this terminal outputs approx a 7 volt AC sine wave. This signal goes to "monitor", tach and hour meter.When your battery light comes on, verify you still have the AC at this terminal referenced to a good ground.

 

[Delmer]

The W wire drives the tachometer, if the tachometer is working, then the W wire is delivering the signal from the alternator. Does the tach work when the alternator light is on?

I said the accessories are a separate issue, but if they're shorted out and only randomly coming on, then that random short/voltage drop could be your issue. If the test lead/volt meter reading at the alternator doesn't show anything, then I would investigate any electrical components that don't work, if you can't figure them out, then remove the fuse, or disconnect the hot power feed until you do figure them out. This is how machines burn up.

I haven't heard of oil causing issues specifically. It will soften some plastics and could lead to shorting out. The dirt could lead to binding of the harness and contribute to cracking over time.

 

[dbs]

The W wire drives the tachometer, if the tachometer is working, then the W wire is delivering the signal from the alternator. Does the tach work when the alternator light is on?

I said the accessories are a separate issue, but if they're shorted out and only randomly coming on, then that random short/voltage drop could be your issue. If the test lead/volt meter reading at the alternator doesn't show anything, then I would investigate any electrical components that don't work, if you can't figure them out, then remove the fuse, or disconnect the hot power feed until you do figure them out. This is how machines burn up.

I haven't heard of oil causing issues specifically. It will soften some plastics and could lead to shorting out. The dirt could lead to binding of the harness and contribute to cracking over time.

Your right the tach does not work but only when the alternator light is on, I'll look for a short. Thanks

 

[HankTO]

Check to make sure you have a good clean ground connection

 

[dbs]

I replaced the accessory relay and it fixed all electrical problems. It is a selenoid located under the control console in the cab, thanks for everyone's help.

 

[HankTO]

Nice!