Recently purchased a Komatsu D39PX-23 and have put about 80 hours on ot with no problems until yesterday. My operator was backing up and it just shut off. No accessories will work, horn, radio, dome light, monitor panel, accessories blower or anything. They went and tried to bull out one of the fuse links that was a 30a and it broke. I picked up a new one and replaced it and nothing. The operation manual shows it should have two that are 120a. Not sure why someone put a 30 in and doubt it would cause any problems having a lower amp fuse link but I'm searching for anything to point me in the right direction. I checked all of the automobile style fuses and checked the ignition switch for 24v. I have 24v to the red wire and when I turn the ignition to the on position the acc wire is hot but still no accessories work. I heard about some models having an in line smaller wire type fuse that would burn out but i haven't been able to find anything. Any tips on where to look woukd be greatly appreciated!
Some machines have a fusible link in the alternator power out cable or breaker that will shut down power out of alternator if too much power is being used, or if breaker or fusable link is getting weaker. Cat has them on most machines. Get a schematic from dealer on alternator circuit and post it and we can see what needs to be checked out. Have you checked all fuses that are listed in operators manual. If you don't have one, they are worth the information that takes out guess work. Simon C
Yes sir. I have the shop, parts and operation and maintenance manuals. I'll see if can find the alternator wiring diagram and post it. I seen the following in another post and was going to check into it tomorrow. "I am not sure on the D21 but the large Komatsu dozers have a relay by the starter so that you can not start with the engine running - the relay is ran off of the R terminal on the alt. If the doide goes out on the alt there is power coming out of the R terminal and can not start the machine. Trun the key on and see if the battery light comes on if not check the r terminal on the alt - if has power that is the problem should only have power if alt is turning." Thank you for your help Simon.
Your machine may have a large positive disconnect solenoid by the battery box. The power has to be hot on both of the large terminals for the machine to crank, also for the rest of machine to get power. Check if you have one. It is powered by the key switch and runs everything else. Simon C
If only 1 side of solenoid has power you have a control circuit problem from key switch to positive battery disconnect solenoid. Needs to be checked. Simon C
Well I thought I found it. The 10a accessory fuse was blown. I replaced it and everything powered up fine, it was running while I was putting everything back together, I slammed the door and the fuse blew again. I replaced the fuse everything was fine, I shut the other door and it blew again! Now replacing the fuse does nothing. What the heck? Got to checking the fuse block, with the battery disc on i have no power, with the disconnect off, I have power on the other side of the fuse block from where it should be. Then I checked the ground cable and where it grounds to the frame I have 24v! Some how I'm getting voltage all over. Guess I have a cable shorted or something.
Sounds like a wire is shorting when you close the door. I'd look for cracked or worn insulation on the wires. I had a really weird problem with a stripped wire on my Cat. Of course it was in a group of wires and on the bottom where it was impossible to see. Mechanic friend came out and jiggled the wires and we saw sparks. Had to take the loom off to expose the wires.
Update. Got it running again and was able to shut both doors. I was by myself so I went thru and moved, jiggled every wire I could then just decided to put the negative cable back on (even though it was sparking when I put it on) and try it again. With it running i went back thru moving wires trying to get it to stop to no avail. This machines wiring harness looks new, everything is in loom and bundled nicely with lables and hold downs securing it in place. It's hard ti believe that a wire got broke inside the loom but I guess it's possible. Thanks for the help.
It wouldn't be that unusual to have a bad wire(s) inside a loom. I ran a new wire from the alternator to the ammeter along the original wire on my Cat. I don't know if the original wire had a blown fusible link or what was wrong but it wasn't working. Bob/Ont suggested it's much easier to run a new wire than try to find a short inside a loom. I put a 30 amp fuse on the new wire just for piece of mind.
Seen a Cat 140G grader that had multiple wires that broke in middle of harness with no markings. Was faulty from factory. Had to change out the harness in the end. Just for your info, a ground cable can show voltage in it before it enters the battery. Simon C
Thanks for that info Simon. I was scratching my head on that one. Good thing is it's been running fine since so I'll keep my fingers crossed.