Kubota KX121 safety lockout

topstoy · May 26, 2019

I finally dug into it and I found the switch buried in there. Pulled it out. Exercised it on the bench with full strokes as it only moves about 1/4 stroke in its normal function/position. Re-installed and it works for now. I found the part number and will get one to have on hand if it fails again. Thanks to all you folks that replied.

Cataclysm · May 26, 2019

Great! Glad you got it fixed!

To follow up on my machine, I got it in the shop and confirmed I had 12v going to the solenoid. Thinking maybe I had a broken wire right at the solenoid I worked the wiring all around while my son watched the controls to see if they would lock. Everything stayed unlocked no matter how I worked the wires.

I checked the connector over carefully and noticed the lock on the connector is broken off. The only thing I can think of is the connector slid out enough while I was hauling the machine to loose contact. I will keep an eye on it and see.

Cataclysm · May 26, 2019

OK, next round. I've been using the u45 a little this weekend. Went to move it and sure enough, safety lock lever won't release. At least it was at the shop and I had time to work through it.

Solenoids and valve block all check out several different ways as good. Next I put the pressure gauge on the inlet side of the safety valve. Zero hydraulic pressure. Next I check at the accumulator, zero pressure. Then I checked at the pump, correct no load pressure and correct pressure under a load/against the main relief valve. (dozer blade still works regardless of the safety locks.)

Next I took the pilot filter out. It looks ok but that doesn't mean its flowing. I back flush it a bit with hydraulic fluid and re-install. Now everything works just fine and I have correct no load pressure at the safety lock valve inlet.

Another possibility. The pilot filter/safety lock valve picks up pressure from the load sense block. Its possible something is wrong in there and occasionally not supplying pressure to the safety lock valve. I'm not sure how that could happen but there isn't anything else in the system.

I will get a new pilot filter next week and install it and see if that fixes it.

topstoy · May 28, 2019

Cataclysm said:
OK, next round. I've been using the u45 a little this weekend. Went to move it and sure enough, safety lock lever won't release. At least it was at the shop and I had time to work through it.

Solenoids and valve block all check out several different ways as good. Next I put the pressure gauge on the inlet side of the safety valve. Zero hydraulic pressure. Next I check at the accumulator, zero pressure. Then I checked at the pump, correct no load pressure and correct pressure under a load/against the main relief valve. (dozer blade still works regardless of the safety locks.)

Next I took the pilot filter out. It looks ok but that doesn't mean its flowing. I back flush it a bit with hydraulic fluid and re-install. Now everything works just fine and I have correct no load pressure at the safety lock valve inlet.

Another possibility. The pilot filter/safety lock valve picks up pressure from the load sense block. Its possible something is wrong in there and occasionally not supplying pressure to the safety lock valve. I'm not sure how that could happen but there isn't anything else in the system.

I will get a new pilot filter next week and install it and see if that fixes it.

Good troubleshooting.