L3901HST Won't move

onyebike

New member

Equipment
L3901, PD25 post hole digger
Aug 25, 2017
8
1
3
Fort Worth, TX, USA
Hi my L3901 starts OK and engine runs fine but as soon as I try and go forwards or back the engine dies. First I thought of the seat switch but got zero resistance with the lever down. Tried jumping the switch to try and identify the problem and the engine still dies. What other switch would cause the engine to stop. Not the PTO switch as that won't allow the engine to start at all.
 

TheOldHokie

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L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
Apr 6, 2021
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windyridgefarm.us
Hi my L3901 starts OK and engine runs fine but as soon as I try and go forwards or back the engine dies. First I thought of the seat switch but got zero resistance with the lever down. Tried jumping the switch to try and identify the problem and the engine still dies. What other switch would cause the engine to stop. Not the PTO switch as that won't allow the engine to start at all.
Long shot but make sure the seat is actually coming fully down. I had this problem when I left a wrench under the seat.

Dan
 

BigG

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Equipment
l2501, FEL, BB, Rotary cutter, rake,spreader, roller, etc. New Holland TL80 A
Sep 14, 2018
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West Central,FL
Check to see that the range selector is in medium or low.
 

Henro

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B2910, BX2200, KX41-2V mini Ex., Beer fridge
May 24, 2019
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Sounds like time to round up an electrical diagram for your tractor.

How many wires on the seat switch? Sounds like two if you jumped it out. If four, maybe you did not jump it out correctly.

Logic seems to indicate that the tractor should move OK if the seat switch is working properly.

But you need to get more specific than what logic dictates, when pertinent details may be missing. An electrical diagrame may provide the details you need to solve the problem.

EDIT: I do not see posts 2 or 3 for some reason...confused about this...thread jumps from post 1 to post 4 on my screen...

2nd edit: after moving on and coming back, I now see all the posts..go figure...
 

onyebike

New member

Equipment
L3901, PD25 post hole digger
Aug 25, 2017
8
1
3
Fort Worth, TX, USA
Sounds like time to round up an electrical diagram for your tractor.

How many wires on the seat switch? Sounds like two if you jumped it out. If four, maybe you did not jump it out correctly.

Logic seems to indicate that the tractor should move OK if the seat switch is working properly.

But you need to get more specific than what logic dictates, when pertinent details may be missing. An electrical diagrame may provide the details you need to solve the problem.
I think I have that covered, 3 wires on the connector, outer two (black and orange) should be zero resistance when the seat is down. I jumped those. The center wire (blue) and the black should be zero when the seat is lifted up.
 

Henro

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Equipment
B2910, BX2200, KX41-2V mini Ex., Beer fridge
May 24, 2019
5,781
2,965
113
North of Pittsburgh PA
I think I have that covered, 3 wires on the connector, outer two (black and orange) should be zero resistance when the seat is down. I jumped those. The center wire (blue) and the black should be zero when the seat is lifted up.
OK. Maybe you do.

But without a wiring diragram, which you may have said you have, and I may have missed, how do you know for sure what you are jumpering out is correct?

Three wires indicates that one side should be closed and one side should be open.

Are you sure you are jumpering out the side that should be closed?

Not trying to be argumentative, just trying to help.
 

lugbolt

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Equipment
ZG127S-54
Oct 15, 2015
5,205
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Mid, South, USA
the switch is a "window" switch.

It makes contact at a certain angle of the paddle. Outside that "window", it is open. The WSM outlines it pretty well.

On a 3901 you can do a quick easy diag using the beeper.

start with key OFF
hold down both of the yellow buttons
now turn the key on while holding the buttons down.
Look where the hour meter is. Should say "a". If it does, let go of the buttons. Now hold them down again until you get a beep. Soon as you hear the beep let go of the buttons. Meter should say 1: and then some numbers. Those numbers don't matter for what you are doing.
now you can actuate your switches. Each one you activate should make a beep. HST pedal forward, should beep. Return to neutral, should beep. Park brake lever, should beep. PTO switch, should beep. Now flip the seat up and actuate the seat switch. It should beep somewhere in the middle. If not the wiring or switch is suspect. I've seen the wires get ripped out of the connector before. U can test all of the switches that way. It is super super easy!
 
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ve9aa

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TG1860, BX2380 -backblade, bx2830 snowblower, fel, weight box,pallet forks,etc
Apr 11, 2021
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NB, Canada
Parking brake on? (sorry, had to ask...I've done it!)
 

bmblank

Well-known member

Equipment
2020 L3901HST, LA525 Loader, 66" Q/A Bucket, PFL2042 Forks, Meteor SB68PT Blower
Mar 4, 2015
662
292
63
Cadillac, MI
Having the parking brake set won't kill the engine but it will make the HST whine pretty loud :mad:

Dan
It would kill mine if I don't back off. Just a little bit of brake and it locks up tight.
 

TheOldHokie

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Lifetime Member

Equipment
L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
Apr 6, 2021
8,734
4,477
113
Myersville, MD
windyridgefarm.us
It would kill mine if I don't back off. Just a little bit of brake and it locks up tight.
You have much better brakes than mine. I have forgotten and driven mine considerable distance before the sluggish power and loud whine got my attention.

Dan
 

onyebike

New member

Equipment
L3901, PD25 post hole digger
Aug 25, 2017
8
1
3
Fort Worth, TX, USA
the switch is a "window" switch.

It makes contact at a certain angle of the paddle. Outside that "window", it is open. The WSM outlines it pretty well.

On a 3901 you can do a quick easy diag using the beeper.

start with key OFF
hold down both of the yellow buttons
now turn the key on while holding the buttons down.
Look where the hour meter is. Should say "a". If it does, let go of the buttons. Now hold them down again until you get a beep. Soon as you hear the beep let go of the buttons. Meter should say 1: and then some numbers. Those numbers don't matter for what you are doing.
now you can actuate your switches. Each one you activate should make a beep. HST pedal forward, should beep. Return to neutral, should beep. Park brake lever, should beep. PTO switch, should beep. Now flip the seat up and actuate the seat switch. It should beep somewhere in the middle. If not the wiring or switch is suspect. I've seen the wires get ripped out of the connector before. U can test all of the switches that way. It is super super easy!
Thanks for that great test. Checked each one of the switches and they all beep. Now I'm really confused.
 
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onyebike

New member

Equipment
L3901, PD25 post hole digger
Aug 25, 2017
8
1
3
Fort Worth, TX, USA
Just grasping at straws here. What happens if its in neutral and/or the clutch is depressed when you press the HST pedal?

Dan
No change, same problem. New seat switch arrived today and that didn't fix the issue. Pretty much resigned to having to haul it off to the dealer.
 

JG1358

New member

Equipment
Kubota L 3901 HST
Nov 8, 2022
2
0
1
Stahlstown PA
No change, same problem. New seat switch arrived today and that didn't fix the issue. Pretty much resigned to having to haul it off to the dealer.
No change, same problem. New seat switch arrived today and that didn't fix the issue. Pretty much resigned to having to haul it off to the dealer.
Did you get the issues resolved? My L3901 HST is doing the exact same thing. starts and idles perfect but as soon as you push the forward /reverse it dies, if you engaged the PTO switch it dies. I get an Operator Presence code upon start up. Replaced the seat switch and contact switch under the foot pedal and brake but no change. I Tried it in H, M, L, and neutral position no change? Even with the new seat switch I can get off the seat and the engine will still idle? confusing! Any insight would be appreciated