John Deere 6820 4wd not working

[Fuzzy]

Looking for help with 4wd on 6820, it not engaging on the switch (no lights come on) or when braking.
Is it the solenoid or internal to gearbox ?

 

[marco]

Looking for help with 4wd on 6820, it not engaging on the switch (no lights come on) or when braking.
Is it the solenoid or internal to gearbox ?

Check the bulb, is it lighting up when you turn on the ignition?

 

[Fuzzy]

Check the bulb, is it lighting up when you turn on the ignition?

Will a failed bulb stop it engaging ?

 

[Phil-the -farmer]

On my 6920 there are two wires going to a solenoid underneath the rear axle which are a bit exposed. Used to get damaged if I reversed in tall rape crops disengaging the 4wd. May be worth crawling underneath and having a look?

 

[Timbo]

No power to solenoid is 4wd. Solenoid powered is 2wd.

Something is keeping your solenoid powered all the time.

 

[Stephen E]

Check the brake lights. The switch on the brake pedal should also engage 4wd when applied.

 

[Fuzzy]

Check the bulb, is it lighting up when you turn on the ignition?

No, bulb was blown, so replaced it (borrowed from hms light) and light is now working. But still no 4wd.

 

[Fuzzy]

No power to solenoid is 4wd. Solenoid powered is 2wd.

Something is keeping your solenoid powered all the time.

Thanks, so i disconnected plug from solenoid (round one at rear of drop box?) to remove power and made no difference.
Is it possible solenoid has failed in open (powered position ) ?

 

[Fuzzy]

Check the brake lights. The switch on the brake pedal should also engage 4wd when applied.

Thanks, so i have tractor hooked up to the parked merlo. i have it in bottom gear rear wheels spinning on wet concrete and when pressing brake pedal(brake lights on) it does not engage 4wd.

 

[Timbo]

Thanks, so i have tractor hooked up to the parked merlo. i have it in bottom gear rear wheels spinning on wet concrete and when pressing brake pedal(brake lights on) it does not engage 4wd.

Internal problem then.

 

[Mur Huwcun]

Thanks, so i disconnected plug from solenoid (round one at rear of drop box?) to remove power and made no difference.
Is it possible solenoid has failed in open (powered position ) ?

Not on a Deere but have seen some locked through dirt in valve but usually stuck in 4wd. First check your prop splines etc then pop the solenoid out to check.

 

[Fuzzy]

Internal problem then.

Looking that way, although it seams a bit odd the bulb failing at the same time as mechanical failure ???
Think i will drain oil, then remove and check solenoid first. ...

 

[Fuzzy]

Internal problem then.

Is it best to try drop box first ? or tilt cab and take gearbox out ?

 

[Planttech]

Take the plug off the coil and check. If still no 4wd drive it’s internal. If fuse blows or wiring fault it defaults to permanent 4wd

 

[Fuzzy]

Take the plug off the coil and check. If still no 4wd drive it’s internal. If fuse blows or wiring fault it defaults to permanent 4wd

Yes i have taken plug off and still no 4wd. Is the issue likely to be in the gearbox or drop box ?

 

[Planttech]

Yes i have taken plug off and still no 4wd. Is the issue likely to be in the gearbox or drop box ?

I would take the drop box off first. But have you check to see if prop shaft turns when engaged? Could be from diff fault

 

[Fuzzy]

I would take the drop box off first. But have you check to see if prop shaft turns when engaged? Could be from diff fault

Thanks, unfortunately prop is not turning when 4wd engaged !!!

 

[Mur Huwcun]

Thanks, unfortunately prop is not turning when 4wd engaged !!!

It’s not turning at all? It should turn regardless as the front wheels will rotate it.

 

[Fuzzy]

It’s not turning at all? It should turn regardless as the front wheels will rotate it.

To test it i have the tractor chained to the merlo, then put tractor in lowest forward gear, rear wheels will spin (on wet concrete) but prop not turning with 4 wd engaged.

 

[Mur Huwcun]

To test it i have the tractor chained to the merlo, then put tractor in lowest forward gear, rear wheels will spin (on wet concrete) but prop not turning with 4 wd engaged.

Ahh, right I’m with you, makes sense. Remove and test the solenoid valve first just in case. You should be able to see it moving