Tak TL120

[clovis]

Hi, I am trying to figure out what I think is an electrical problem with a Tak TL120 rubber tracked skid loader with 2700 hrs. After running the machine 20-30 minutes, I begin to hear loud "clunks" in the drive train, and the machine will jerk like the parking pins are trying to engage with the lap bar down. About that time, both sticks go dead. The engine continues to run smoothly. Cycling power, or the lap bar, will sometimes get the sticks back momentarily, sometimes not. Shutting the engine down and letting it sit has worked to get it moving so far, until it warms up and the cycle starts over again. I pulled the relay panel out from in front of my feet and located the lap bar relay. I swapped it with the relay beside it, same problem. I read in this forum about cold solder joints on the larger relays, so I pulled them apart and re-tinned all leads on the circuit boards, same problem. The lap bar triggers a magnetic prox switch. Cycling the lap bar activates the relay. When the problem starts, I can hear the lap bar relay pulling in and dropping out quickly chattering. I am trying to trace the prox switch cable to where it terminates, but am getting lost. I don't have a wiring diagram. I suspect the prox switch is somehow getting hot and failing. My next step is to jump around the prox switch to eliminate it from the circuit.
This is my first post, and appreciate any help anyone might offer. I am a hobby mechanic with limited equipment experience, but enjoy learning and always enjoy the victory of successful repairs. Thank you.

 

[74inchShovel]

Good morning. That machine does not have pins that engage, but a brake pack that is disengaged by hydraulic pressure. The fact the controls go dead is a huge diagnostic tip, these have what is termed “pilot pressure“ ran to them, the controls send this pilot pressure to the actual valve and it is what raises and lowers spool in the control valve. The number one reason machines don’t make pilot pressure is that a safety switch went bad, seat switch, door switch, lap bar, on my machines they ground a safety relay, so if any do not function the path to ground is broken and relay does not close. This relay is what sends power to the pilot solenoid which opens and send pilot pressure out. Check you safety relay, fuses associated with this, try to find a wiring diagram. Incidentally, this is a compact track loader and should be over there, a mod may move it-good luck

 

[clovis]

Thank you for the reply, and explanation on the pilot pressure/safety switch circuit. In a wiring loom near the battery, there is a safety bypass connector wrapped in yellow tape. If I'm thinking right, and I connect it, and problem goes away, that would prove a bad safety. If problem is still there, it will prove a bad ground. I'll try it next.
Thank you

 

[clovis]

Found the problem. This machine has a door that doesn't get used because the glass is out of it. The door switch is mounted to an adjustable bracket that went out of adjustment. When the machine runs over uneven ground, or the bucket bumps something hard, it would loose contact. Adjusted the bracket and problem solved. Thanks again for the help.