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My Komatsu PC28UU-1 Isn't charging Need assistance.

Discussion in 'Compact Excavators' started by Danny Correll, Aug 13, 2019.

  1. Danny Correll

    Danny Correll Member

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    My Komatsu PC28UU-1 Isn't charging Need assistance. The red no charging light is on in the cab. I replaced the original alternator, but still nothing. I see on-line that there is a voltage regulator for it/I'm suspecting it. Anyone know of the location of the voltage regulator?

    Best, Dan
     
  2. John Canfield

    John Canfield Well-Known Member

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    Did you measure the voltage at the alternator with the engine running? At the battery?
     
  3. Danny Correll

    Danny Correll Member

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    John, yes I did. With my new Fluke 117 multimeter I got the same measurement of 12.35 volts DC at the battery when the battery was alone and when hooked up to the new alternator. I then went directly to the alternator w/the AC setting and got 14.28 volts AC. I took pics of the results and can post if wanted.

    Dan
     
  4. 007

    007 Well-Known Member

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    Nowhere on your machine should you be using the ac setting on your multi meter.
    You do get AC out of one of the small terminals but you should ignore this.
    If you are getting 14.28V DC at the alternator output terminal and 12.35V at the battery then I am guessing you have a blown fusible link in the alternator circuit.
    I don't think your machine is equipped with isolation relays which is often the problem on larger machines.
    Do you have a circuit diagram for your machine?
     
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  5. Danny Correll

    Danny Correll Member

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    007, I recall getting nothing after the new alternator w/the DC on. I will add the schematic. Thanks for chiming in! :)

    Komatsu PC28UU-1 Electrical Schematic Diagram.jpg

    Best, Dan
     
  6. 007

    007 Well-Known Member

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    Hi Dan,
    Im sorry i just assumed you had a conventional alternator.
    I am not familiar with your machine but have worked on similar systems by the way.
    Yeah that is going to need a few more steps to diagnose this problem.
    What you have there is a permanent magnet alternator and to be honest they aren't considered good in the industry.
    Ok here is a load of things for you to ponder.
    There is AC at the alternator but your fluke may not read that well and may be a little misleading.
    Its good to know you can see AC there as it means the alt is trying to work but what you need to know is how much work it is doing.
    Because if it was working hard it would lift the battery voltage up.
    A loose fan belt can exhibit same symptom.
    These type of alternators don't do much at idle and need revs to get much out of them.
    I think the alternator is fine.
    You have a device called a current limiter on your diagram.
    The way these things work usually is as follows.
    The alternator is brainless and can over charge your battery so the AC output goes over to the current limiter where it is rectified to DC and sent to the battery terminal of your ignition switch.
    The limiter does nothing more until the battery voltage reaches 14.2V and then begins to redirect the alternator output to ground or to an internal resister to wash off the excess power to maintain 14.2V.
    Here's the thing if the current limiter looses connection with the battery it will wash off all the output and just maintain 14.2 at the limiter.
    So i think it has ether lost that connection or is faulty.
    But if a customer brought there machine to me before ordering an expensive part you would have to be sure.
    Make sure you have battery voltage on wire O2R Number 4 in the block of the current limiter.
    Also what i would do is place a amp meter capable of reading AC amps in series with one of the wires on your alternator.
    This would give you a better indication how much current is flowing.
    Hope this helps.
    Cheers
     
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  7. Danny Correll

    Danny Correll Member

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    007, I appreciate your thoughts and will proceed as you indicated. I'm still not certain where the current limiter is. Perhaps under the control box as I did not see it on the carbody at all. I will look in the box after work today. You also mentioned a fusible link. I see according to the parts list that there may be such an animal in the control box according to the pic. I am adding for you to inspect. Thanks much.

    http://k-part.com/#?k=!0!1!2153!1!12&sb=203-06-57241

    Dan
     
  8. 007

    007 Well-Known Member

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    I had a quick look at the link you sent but they are hard to get much sense out of.
    If you go down to the instrument panel section there is a group of relays and cans shown there but no part numbers or descriptions?
    In the pics shown i would imagine it was the large box with plug in that group.
    They are usually are made of alloy and some times have fins on them to help cool them as they can get hot.
    Usually how they die actually as the fry them self's to death.
    You could check the color codes on alt wires and see if they come trough to that box as well.
    Cheers
     
  9. Danny Correll

    Danny Correll Member

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    I have to work till 5pm PST. I will open up the control panel tonight to look for inspect/test both the fusible link and voltage regulator. Hope I'm able to locate both.

    Dan
     
  10. heymccall

    heymccall Senior Member

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    Should look like this Screenshot_20190815-215644_eBay.jpg
     
  11. Danny Correll

    Danny Correll Member

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    i purchased and received both a voltage regulator off of amazon p/n 119640-77711. I also purchased and received a fusible link p/n 203-06-57241. I was able today to open up and visualize the controls compartment and notice the old voltage regulator, but wasn't able to visualize finding the fusible link which according to the print for the electric compartment should have been in the area of the voltage regulator, but I didn't see it, not did any wires feel as though they were blown. In any case tomorrow I will begin by replacing the voltage regulator. Any suggestions would be greatly appreciated.

    Best, Dan
     
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  12. Danny Correll

    Danny Correll Member

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    Installed the new voltage regulator and the new fusible link. The link wasn't needed, but installed it because I may never need it again. LOL I checked the voltage without it running and also while running at full power. The voltage was the same for all testing 12.24 volts at the battery. I installed a new head beam on the machine which worked w/the original light switch. Hope I can get the charging system going. Still has an open circuit of some type. Also, note worthy is that the only fuse spot on the machine that has no fuse in it is called the "O" circuit. The circuit area for this fuse does not indicate any circuits that are on it, which when putting a new 20 amp buzz fuse in, it quickly fries. Don't know that this is part of the problem, but everything else on the machine works including the horn.
     
  13. 007

    007 Well-Known Member

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    You need to use your fluke and check all the wires in the plug of the regulator when it is running.
    Using your circuit and heymccall's photo of the plug pin connections as a reference.
    By the way you will get the same symptoms if the reg has lost its connection to ground as well so if you get 14V at the reg check B+ and Ground reference.
    Because the alternator is AC it has no reference to ground so both B+ and ground have to be established at the regulator.
    Cheers
     
  14. Danny Correll

    Danny Correll Member

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    007, you were right! Tonight I put in the new ignition switch. Still the same voltage without the engine running and with the engine running. I began to search for problems with the wiring and found a bundle of ground wires that were all together and they were loose on the bolt. I pulled them off, cleaned them and then re-assemble them. We finally have a charge rate. It went from 12.45 volts to 13.68 volts. The battery charging light is still on. Will it go off when the battery gets more charged or is that still a problem? Also I still have one fuse area that blows a fuse immediately. Whats the best way to proceed with that?
     
    Last edited: Aug 20, 2019 at 6:14 AM
  15. 007

    007 Well-Known Member

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    Ok that's good you are making progress.
    You are charging now but the battery has a ways to go before fully charged.
    Yes you still have an issue with the light.
    Your system has a separate relay to put the light out called Charge indicator on your diagram.
    I imagine this got quiet a workout when the regulator lost its earth and the voltage went very high there.
    It may be damaged but i would do some checking with your meter before condemning it.
    It senses what is happening from that wire on the reg called out2 and decides when to put the light out.
    Now im not sure what it is measuring whether it is AC from the Alt or a DC signal from the Reg.
    It needs a good earth as well i see so was that in those earth wires you cleaned?
    If you see what you can measure on that wire when running and come back to me if you like.

    Its normal to have spare slots in the fuse box but unless wired usually go nowhere so is unusual to have a connected circuit and blowing fuses.
    If the circuit you provided is correct you should only have 4 operational fuses, how many do you have?
    The wire on the down side of the fuse that is blowing is it factory, does it go into the loom?
    What size is it, is it easy to see where it goes to?
    An old trick to send some power down the wire just as a test is to push some wires across the fuse clips with a head light globe wired across it.
    The bulb will light up if it is a full short to ground some where but at least you have some current going down that wire that gives you time to go around the machine and identify the wire and or item with a problem.
    Post a picture of your fuse box and wires behind might help.
    Cheers
     
  16. Danny Correll

    Danny Correll Member

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    007, didn’t get a chance to work on the machine tonight because we went for a pontoon ride. Not sure tomorrow night we will either because that will be a birthday party. However; I did take a few pics the other day that showed the fuse box. Please note the one where the fuse is missing that is the one that burns out I took a picture yesterday of both sides so you can see the color wires that are there.

    upload_2019-8-21_0-2-24.jpeg
    upload_2019-8-21_0-3-51.jpeg upload_2019-8-21_0-6-26.jpeg upload_2019-8-21_0-5-23.jpeg
     
  17. Danny Correll

    Danny Correll Member

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  18. Danny Correll

    Danny Correll Member

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    upload_2019-8-21_0-17-7.jpeg upload_2019-8-21_0-18-18.jpeg upload_2019-8-21_0-17-36.jpeg
     

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  19. 007

    007 Well-Known Member

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    What a mess!
    Its hard to tell if your circuit is not correct for your machine or it has just been messed with over the years.
    Firstly on the fuse panel all of those rusty screws should be replaced or cleaned.
    Terminals as well are going to give you no end of future problems if you don't clean them all up.
    I am guessing of course but i think i can work some of it out.
    The battery connection to to ignition switch was un-fused in the circuit but i think some one shuffled all the wires off one of the fuses to free one up.
    So it looks like they have cut into battery circuit (large black with red trace) and put that through second fuse down.
    The top fuse which is blowing was only associated with the charge system and light.
    So on top fuse has ACC on one side and other two white with red and a yellow with blue and two red dots.
    I am guessing one white&R goes to Reg, one white&red goes to indicator relay and yellow goes who nows as you have to trace that as i think that got put on that fuse in the shuffle.
    So if you undo that screw and separate the three wires one of them has a short to ground.
    Maybe be use big bulb instead of fuses to check.
    Maybe ohms or continuity setting on your meter might find which wire it is if the short to ground is solid.
    See how you go.
    Cheers