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komatsu PC-120-6 no start no power

D

Diesel Dan 92

Well-Known Member
Joined
Jul 20, 2014
Messages
60
Location
West of Lansing, MI
Operator calls this morning says machine is dead.

No crank, no power to monitor panel or blower fan anything, etc.

Have 23.5 volts at batteries, checked and cleaned connections and grounds in the battery box, no change.

Have voltage at hot wire at ignition, shows kinda low, like 16.6v ?

Turn key to "on" and voltage goes to zero ?


I'm stumped.
 
J

Jgm

Well-Known Member
Joined
Jan 30, 2019
Messages
125
Location
Germany
Sounds like a bad battery relay, you can jump it for a temp fix but should be replaced.
 
J

Jgm

Well-Known Member
Joined
Jan 30, 2019
Messages
125
Location
Germany
You will have no power to monitor or gauge power, if you jump your battery relay then you will, on the battery relay you have 2 big connectors, (they come from battery +/-) 2 smaller ones, if you go from the + to the smaller one with a small jumper wire then it should work. I'm not sure with that model, but by the bigger models they have an extra inline fuse behind your batteries that is connected to the battery relay, which that fuse powers your monitor as well
 
John C.

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,870
Location
Northwest
Occupation
Machinery & Equipment Appraiser
You have an old machine. Have you checked the fuse panel and fuses before doing anything else? It's been quite awhile but they also used to put a fuseable link down stream of the battery disconnect that fed the computers and monitor. It should be just above the battery disconnect and have a plastic flag on it.

Is the battery disconnect working or not? If you put your hand on the battery disconnect and have someone in the cab turn on the key, you should feel and hear it snap in. Do you have a service manual and have you done a net search on information about these machines. I know I have posted on this board how the disconnect works and how to fix them.
 
D

Diesel Dan 92

Well-Known Member
Joined
Jul 20, 2014
Messages
60
Location
West of Lansing, MI
John C. said:
You have an old machine. Have you checked the fuse panel and fuses before doing anything else? It's been quite awhile but they also used to put a fuseable link down stream of the battery disconnect that fed the computers and monitor. It should be just above the battery disconnect and have a plastic flag on it.

Is the battery disconnect working or not? If you put your hand on the battery disconnect and have someone in the cab turn on the key, you should feel and hear it snap in. Do you have a service manual and have you done a net search on information about these machines. I know I have posted on this board how the disconnect works and how to fix them.
Click to expand...

The battery disconnect works now that I have run a new hot wire to the ignition.

The larger wire on top is direct battery voltage, the red wire is the new one I ran to the ignition. The bottom large wire and bottom small wire get voltage upon turning key to “run” position. The top small wire has continuity to ground.

The machine starts, operates and moves as it is now, just nothing out of the gauge / control panel.

The three loops above the disconnect are fusible links, they appear to be fine.
 

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C

Charles Hudson

New Member
Joined
Feb 3, 2023
Messages
2
Location
South Carolina
I am really embarrassed as to what the problem was!!!! The fuse block cover was lost years ago by a previous owner. Needless to say it is not the easiest to see in it's location. I diligently removed each fuse and checked them. Now what I didnt notice(I am going to blame it on age and bad eyesight) was that there was a fuse MISSING. The last fuse in the block was not there and I didnt realize it. It had fallen out and was laying in the floor. I took a chance, plugged it in and everything was good. It felt a little loose putting it back in,,,,but not THAT loose. The gremlins are out and about I guess.:D:D
 
D

Dai digger

New Member
Joined
Mar 27, 2023
Messages
1
Location
Swansea
Had similar problem
Changed the stereo,and now there’s no power to nothing
Wish I’d left it alone now.
 
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