I have a PC150LC-6k excavator. I turn the to the on position and hear a click but no response from the monitor and no power to the rest of the machine. I bought a new battery solenoid and still the same thing. So I ran a jumper wire from the accessory leg of the key switch and when turning the key everything turns on the machine starts. But when turning the key to the off position the machine will not shut down until I remove the jumper wire. When turning to the on position the accessory position have 24 volts. But in the off position before the jumper is removed it’s holding 12volts. Not sure what’s going on.
I ran into this on a PC120-5. While the relays look the same, I had to buy a genuine komatsu battery relay. Same ordeal you're chasing. Did you buy a genuine Komatsu battery relay?
Can you post a photo of the relay, I may have a fix.
I did get the relay right from Komatsu. I will send a pic as soon as I can.
I had the same thing happen on one of my John Deere tractors. Battery was good, turn key on: nuthin. Pulled all fuses and relays out several times and checked all with a meter. All good. Put them back in. Try again: nuthin. Got pissed off, went down to the auto parts store and purchased all new fuses. Installed them. Tried it again. Now, I have all my dash lights and the tractor started. Only thing I could think of was the main key switch fuse had just enough material left in it to pass a continuity test, but not enough material to pass actual power to the relays.
Hummm that sounds like a possibility. Maybe the ignition is bad.
This is the old one the new one is shaped differently, but same concept, and they both do the same thing as far as not shutting the machine off or turning it on when power is sent to it by the key switch without the jumper
Looking at the schematic, the BR terminal on the relay goes through H02 plug, then travels through D13 diode, through X07( MIC17) plug to BR terminal of Key switch. It does not go to the ACC terminal of Key switch on the schematic that I have for PC 200-250 LC-6 Ser#82001 and up. Maybe your is wired different. It is a brown wire that powers the BR terminal of the relay. The key switch Battery terminal gets its power from Fuse Box Fuse14. The Battery relay has 2 Fusible Links just outside the box, that being M11 and M14. they are both fed by White wires from the Battery Relay. One comes from the Battery terminal , the other comes from the Motor terminal of the Battery Box Relay. Hope it helps. Simon C
Thank you very much for the information!! I’m thinking the diode could be bad. It’s not supplying the power to the battery solenoid, but once it is powered with the jumper wire it back feeds and will not shut the machine down. Does that sound possible?
Diode 13 forwards the power from the Key Switch BR Terminal to the BR Terminal of the Battery Relay. It stops power from feeding back. Diode 13 is in the cab on the wall of the machine in the back corner below the control panel, and below plug in H1 and H2. It needs to be checked along with the fusible links beside the battery box. Simon C
Make sure fuse #2 and !4 are both okay in fuse box. Test with a test light not a multimeter, in case fuse is burn't and rewelded. Yes I had this on a PC250 years ago. Simon C
Ok thank you very much!
I have the same set up on a Hu Flug Dung tractor, was getting power to it via the small wires and nothing happening at the larger terminals. Pulled it apart and moisture had got in which caused corrosion on that switch,cleaned all that up and hey presto it works. Maybe you can be as lucky.
That worked for me in the past, but not this time unfortunately.
Symptom: Key turn → Click (solenoid engages) → No power to monitor/machine. Your Fix: Jumping accessory wire at key switch → Machine has full power and starts. New Symptom: Key in OFF position → Machine stays running (because of the jumper). Critical Clue: You measured 12V on the accessory terminal when the key is OFF and the machine is running via the jumper.
I would like to take the time to thank all the help that you gentlemen provided for me. Especially Simon C. I was able to determine that I did have a bad diode and was able to get my machine back up and running properly with the key switch.
At least you replied back to help out others who may have similar problems and helps us old guys with our schematic diagnostics. Any more problems, fire away. We can only help what we know, sometimes someone else has seen the problem. Simon C