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No start. Komatsu PC50

redline808

Well-Known Member
Joined
Jul 4, 2007
Messages
101
Location
Hawaii
2006 PC50mr-2

The other day the dash/display was randomly beeping while I was operating. I noticed some moisture under the cover. I removed it and dried it. Re-installed it, and it seems fine, all the functions work, went to start the machine and I just get a relay clicking when I turn the key as if the battery was extremely low, I changed the battery and I get the same symptoms. I don't believe its the starter because the other day it cranked quickly and started with out issue. Any ideas?

Thanks!
 

redline808

Well-Known Member
Joined
Jul 4, 2007
Messages
101
Location
Hawaii
Okay, update.

Machine runs! turned out being the starter after all. I guess being in Hawaii and all of our humidity caused 2 of the brushes in the starter to get stuck out/off the commutator with only 2 contacting the commutator, there was not enough power to turn the starter. I figured this out by trying to jump the starter and nothing happened. Took it out, seen the stuck brushes, cleaned them up, reinstalled and it fired right up.
 

shorefishin

New Member
Joined
Apr 25, 2017
Messages
2
Location
Hawaii
redline, any experience with a PC45? I'm on Maui having trouble with clicking starter, any tricks to get the starter out? Starter solenoid?
Thanks
 

Bjarn

Member
Joined
Jan 3, 2014
Messages
7
Location
Canada
redline, any experience with a PC45? I'm on Maui having trouble with clicking starter, any tricks to get the starter out? Starter solenoid?
Thanks
redline, any experience with a PC45? I'm on Maui having trouble with clicking starter, any tricks to get the starter out? Starter solenoid?
Thanks

The starter is held on by two different size bolts. The bottom bolt is the hard one to access, but a short 17mm wrench gives you just enough room so you can crack it, it then easily unscrew by hand. If you can't find a short 17mm wrench, then cut a regular size 17mm wrench in half. Use a mirror to see where the wires connect. It is a tight fit and it might be advisable to cover the bolt ends to prevent an accidental future short. You can buy a new starter from Komatsu but it will cost about $600, or you can pick up a Dixie starter on Ebay for about $125 including the solenoid.
 

shorefishin

New Member
Joined
Apr 25, 2017
Messages
2
Location
Hawaii
I will give it a shot. I will need a 4 or 5 inch 17mm? Boxed end wrench? It is an older machine "98" 3600hrs Probably needs a new starter? Will let you know if I get it out.
Thanks
 

DoyleX

Senior Member
Joined
Feb 2, 2013
Messages
571
Location
Minnesota
Occupation
Lever Puller, Gear Jammer, Pipe Twister
There is a safety solenoid under the seat that goes bad. Before you swap the starter check for proper voltage at both the solenoid and starter hot.
 

Guillermo Lopez

New Member
Joined
Jun 25, 2022
Messages
1
Location
28037
I have a komatsu pc55rm2 which I believe is the same as a pc50.
I had trouble starting it once in a while but now I have no power to anything but the battery has 12volts.
I purchased a service manual but really does not illustrate the locations of components.
According to MY manual, positive current flows from battery to a "fusible link" then it should supply voltage to F2 (fuse #2?)
I have no power at the ignition switch.
If the safety relay would be defective the engine would not start but the ignition switch would be powered. I am right with this statement?
There is a relay R1. I don't know the location
I believe the fusible link is the one located at the positive battery terminal.
F2 it is on the fuse box on front of the seat.
I worked for 40 years as an auto technician but this is out of my lead.
Thanks
 

CM1995

Administrator
Joined
Jan 21, 2007
Messages
13,248
Location
Alabama
Occupation
Running what I brung and taking what I win
Welcome to the Forums GL! Glad to have you.

Unfortunately I am no mechanic and have nothing to offer but we have several knowledgeable wrenches here that can help you out.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I don't remember ever putting hands on you model of machine. If it is like all the rest of the Komatsu machines that I have put hands on there will be a battery disconnect. The fusible link will be in that compartment somewhere. Power to the key switch usually does not go through the fusible link though. One wire will be hot to the fuse in the cab, then to the key switch. The key switch when turned on will ground the circuit which will cause the battery disconnect to close and power up the electrical system in the machine. There are two types of disconnect switch. The video on the link below describes both types.

 
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