If the arms lower by themselves, is the problem the kit or the hydraulics?
The cause is nearly always hydraulic. Cut the supply to the kit and set the lever by hand; if the lowering goes on, the trouble is the hydraulics, not the kit.
If the arms come down slowly under load the cause is nearly always hydraulic: the cylinder seal or internal leakage in the control valve. The way to tell is to take the kit out of the equation. Cut the supply to the kit, leave the mechanism free and put the lever in the transport position by hand; if the lowering continues, it has nothing to do with the kit.
The test that tells them apart
- Disconnect the supply wire of the kit and leave the mechanism free.
- Put the lever in the transport position by hand, lift the equipment and wait 10–15 minutes.
- If the arms still come down, the problem is entirely in the hydraulics.
The meaning of the test is this: with the kit removed or unpowered it produces no command at all, so it cannot move the lever. The only actor left is the hydraulic circuit. This behaviour is called hydraulic drift and its source can be narrowed down systematically. Do not keep the waiting time short: a few seconds of watching can hide a slow leak, and the creep only becomes measurable over minutes.
The source according to the symptom
| Symptom | Likely source | Verification |
|---|---|---|
| Continuous lowering with the lever in neutral | Internal valve leakage or the lock valve | Does it lower with the lever in manual neutral too? |
| Lowering only under a heavy load | The cylinder seal | The lowering slows when the load is lightened |
| Lowering that speeds up as the oil heats | Viscosity and a worn element | Separate measurements cold and hot |
Hydraulic causes: internal leakage at the cylinder seal, wear on the valve spool, low or contaminated oil, a blocked filter. If there is a pilot operated check valve or a load holding valve mounted directly on the port at the cylinder port, the leak can come from those elements themselves. For the effect of temperature see the effect of oil temperature on lever response; if there is a leak visible from outside, the effect of an oil leak on the kit has to be assessed separately.
The indirect cause on the kit side
If the cable length was set wrongly at installation, the lever may not seat fully in the transport position. If the cable is slacker than it should be the kit cannot pull the lever far enough, and if it is attached tighter than it should be the lever hangs at an unstable point. The cable is not detached from its original end on the tractor side; only its outer end is attached to the cable entry socket of the kit and the length is set from there. Cable slack is the name of that adjustment, and it has to be checked again as the cable stretches over time.
Safety
Never go under a linkage that comes down by itself. Lower the equipment to the ground or put a mechanical support in place; hydraulic pressure on its own does not count as a safeguard. The rules for working under the linkage hold exactly the same whether a kit is fitted or not. You do not need to raise the equipment high when doing the test either; a height that is enough to see the creep, a position with nobody underneath and a fixed reference point are all it takes.
What to do
Carry out the test first and write the answer down: does it come down with the kit disconnected or not? That single answer splits the job in two and points at the right side before you go to a workshop. If the lowering stops with the kit disconnected, the adjustment is in the cable; reset the cable length and confirm that the lever seats fully in the transport position. If it goes on, hydraulic servicing is needed, and taking a written note of the load, the time and the amount of creep with you shortens the diagnosis.
The full topic: Converting a tractor hydraulic lever to electronic control