John Deere Tachometer Problem

[duanelindsey]

This is regarding a 2008 John Deere 5425. The tachometer worked, but It basically stopped working. When
I first crank it up the tachometer needle stays below 100 rpm.As it is warms up and the engine speed is
increased to over 1000 rpm, I would guess, the needle will move up to between 500 and 800 rpm. When
I idle it back down, the tachometer goes back to below 100 rpm's. I cannot find a cable going from the
tachometer. Is the tachometer electrically run? The hour meter continues to work .
What should I check next. I know this shows my ignorance, but is there any way maybe something like a
blown fuse or some other simple device that could have anything to do with something like this?
Thanks in advance for any help!

 

[dusty3030]

Yes, electronic not mechanical.
There is a ground cable between the engine and the cab at the rear end of the engine. Find it, unbolt it and clean the contact surface and tighten it back down. Also check the battery connections while your at it.

 

[Hoss710]

Check connections like stated above. also check all the wiring near the alternator .If I remember correctly the tach signal is generated from the alternator.

 

[duanelindsey]

Yes, electronic not mechanical.
There is a ground cable between the engine and the cab at the rear end of the engine. Find it, unbolt it and clean the contact surface and tighten it back down. Also check the battery connections while your at it.

Thank you for this information. I did not know it.

 

[duanelindsey]

Check connections like stated above. also check all the wiring near the alternator .If I remember correctly the tach signal is generated from the alternator.

Thank you for this information. As stated above I did not know about it.

 

[duanelindsey]

Thank you for this information. I did not know it.

Dusty, my tractor is an open cab tractor. I have checked the wiring around the alternator and cannot find anything that seems wrong.
I have checked all the connections. I even cleaned the battery connections even though I have not had any problems cranking.
I have a loader on the tractor and it is hard to follow the wiring from the steering wheel to radiator even with a light.
Thanks again for your suggestions. If there is something else, you think off please let me know.