[whybeare123]

I have a John Deere 3720 a day or 2 ago I was using it and I noticed that the rpm gauge needle was only going down to 20. So I shut the engine off and the needle only went down to 20 if I gave it some rpm its go up to 30 and hit the needle stop. I checked the dash and there were no codes. So I cycled the key a few times and then for a second I saw error 08 which is for the throttle position sensor. But the code did not appear again after that. So I unplugged the sensor by the foot throttle and then plugged back in and the needle went down to 0. But now the needle stops at 15 and will not go any higher. I have no idea what is going on or what I could do to fix it either. Any help would be greatly appreciated.

 

[theduke]

You likely have a Battery issue.
Are you still running the factory battery?

This is one of the many signs of its about to die.

If a newer battery ...clean terminals....don't forget to clean/check where the red wire hooks to starter.

This is all gonna seem odd....its just the way it is. Jd's are picky about clean power connections.

You don't say what year tractor ..but from the description of issues "codes" etc...its newer and this is not Uncommon.

 

[whybeare123]

I think its a 2009 or something. The battery is a few years old (its a napa battery) but it works perfectly fine also I cleaned the battery terminals and there was a little bit of corrosion but the gauge still isn't working correctly.

 

[MarkEagleUSA]

The battery is a few years old (its a napa battery) but it works perfectly fine

The only way to determine if a battery is "perfectly fine" is to load test it.

 

[theduke]

There was some model of compact that had issues with the gage cluster.

I forget which one it was .........

Your tach could be on the fritz.....was just a guy in here last week similar to you having tach reading odd.

His battery had suddenly died.

New battery fixed him up .

 

[JD Driver]

I have a John Deere 3720 a day or 2 ago I was using it and I noticed that the rpm gauge needle was only going down to 20. So I shut the engine off and the needle only went down to 20 if I gave it some rpm its go up to 30 and hit the needle stop. I checked the dash and there were no codes. So I cycled the key a few times and then for a second I saw error 08 which is for the throttle position sensor. But the code did not appear again after that. So I unplugged the sensor by the foot throttle and then plugged back in and the needle went down to 0. But now the needle stops at 15 and will not go any higher. I have no idea what is going on or what I could do to fix it either. Any help would be greatly appreciated.

Not sure if this is the same issue or not, but I had a fuel gauge needle on my 4610 that had become loose, slipped in the shaft, and stopped reading zero fuel when the tractor was off. It also read too high when the tank was full.

You might read this posting and see if possibly your RPM gauge needle has slipped and needs to be reset like described in the posting for a fuel gauge. It was a pretty easy fix to reset the needle to the correct resting position. It then read correctly at all positions.

 

[whybeare123]

I don't think the needle is slipping because it went back to 0 after I unplugged the sensor.
I'm thinking I need to recalibrate the sensor because I unplugged it. Because if the sensor is good and it's something else then it still won't work correctly if it's not calibrated. I don't have a load tester and I don't have time to bring the battery away and get it tested then find out the battery is fine just to drive all the way back.
Also if its a problem with gauge cluster then I guess its not going be fixed until next year because we have a pretty bad crop of apples this year so money is tight.

 

[theduke]

Curious on location..... Not in WA. I'm guessing.

More on the Apple farming..........

 

[JD Driver]

I don't think the needle is slipping because it went back to 0 after I unplugged the sensor.
I'm thinking I need to recalibrate the sensor because I unplugged it. Because if the sensor is good and it's something else then it still won't work correctly if it's not calibrated. I don't have a load tester and I don't have time to bring the battery away and get it tested then find out the battery is fine just to drive all the way back.
Also if its a problem with gauge cluster then I guess its not going be fixed until next year because we have a pretty bad crop of apples this year so money is tight.

I am trying to piece this together with almost no information about your tractor.

In the first post you say that you "unplugged the sensor by the foot throttle " after getting a Throttle Sensor error 08.

Based on the "unplugged the sensor by the foot pedal" comment, I am thinking you may have a rare Auto HST tractor with FWD/NEUT/REV lever, no clutch (or other pedals on the left), a single brake pedal on the right and a single "accelerator" pedal on the right under the brake pedal. Is this correct?

The throttle position sensor is up on the engine, not under the floor connected to the accelerator pedal. Neither the throttle position sensor or the accelerator pedal position sensor have anything to do with measuring engine RPM.

On my 4610, engine RPM is measured from a signal output by the alternator. On my 4052R, engine RPM is measured from the outputs of the crankshaft rotation speed sensor and the camshaft rotation speed sensor.

I don't have a technical manual for your tractor, but chances are that engine RPM is measured by one of these methods, or something similar.

I still suspect this is a tachometer gauge issue, not an engine speed sensor issue, since you don't seem to be getting an Err 04 Engine Speed error which occurs when an engine speed sensor has failed.

 

[whybeare123]

I am from Michigan, I don't know much about the tractor and yes it does only have 2 pedals on the right 1 brake and 1 throttle serial number is LV3720R488087. The only thing I've ever had to do to it is general maintenance so I don't know much of anything beyond that on this tractor.

 

[JD Driver]

I am from Michigan, I don't know much about the tractor and yes it does only have 2 pedals on the right 1 brake and 1 throttle serial number is LV3720R488087. The only thing I've ever had to do to it is general maintenance so I don't know much of anything beyond that on this tractor.

Thank you for the additional information. Your serial number puts this tractor in the latest manufacturing group for the 3720.

When I turn the key from OFF to ON and pause, both my 4052R and 6120E go through an instrument test where the analog needles (fuel gauge, temperature, RPM, etc) are moved from their off (rest) position to full scale, and then back to present reading position.

For the tachometer, the needle starts out in the Off position laying on the bottom peg, is swung to the top peg, and then returns to the 0 RPM position (not the lower peg where it started) on the gauge. This makes it easy to see if all the gauges are fully functional across their full range.

Does your 3720 do this kind of gauge test at power-on, and if so, what are you seeing on the tachometer when the key is turned from the Off to the On position (don't turn to start)?

 

[whybeare123]

Yes it does a gauge test. Before I unplugged the sensor the needle would go up to 30 and then only go down to 20 before and after the gauge test. After I unplugged the sensor the needle would go up to 15 and then go back to 0.

 

[JD Driver]

Yes it does a gauge test. Before I unplugged the sensor the needle would go up to 30 and then only go down to 20 before and after the gauge test. After I unplugged the sensor the needle would go up to 15 and then go back to 0.

Thanks. What exactly does the needle do during the gauge test (not before and after)?

 

[whybeare123]

It goes up to 15 then back down to 0

 

[JD Driver]

It goes up to 15 then back down to 0

Based on what my JD tractors do (move all meters to full scale during the power-on self test), this could indicate a gauge problem. Do the fuel gauge and coolant gauge on your 3720 go to full scale during the power-on self test?

At least for my 4052R, there is no calibration procedure for the tachometer gauge in the technical manual. Maybe someone with a technical manual for a 3720 can tell us if there is a tachometer gauge calibration procedure for the 3720.

 

[Shortthrow50]

you need a new instrument cluster.

 

[whybeare123]

All the other gauges self test correctly. But we've had an ongoing issue with the fuel gauge for a long time where it doesn't always read the right amount of fuel. Basically to see how much fuel you have you can either shut the tractor off and then turn the key on (without starting the tractor), or you can just keep driving around until the needle stops going up.