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Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4291
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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Dan tried to help a few weeks back and nothing has worked JA: We'll d

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dan tried to help a few weeks back and nothing has worked
JA: We'll do all we can to help. Tell me a bit more about what's going on so the Heavy Equipment Mechanic can help you best.
Customer: dan knows
JA: Anything else I can tell the Heavy Equipment Mechanic before I connect you two?
Customer: no
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Submitted: 6 months ago.
Category: Construction and Road Equipment
Customer: replied 6 months ago.
I have a Komatsu PC28UU-2. The boom controls do not work. No metal in fluid. Tracks operate, blade operates. Safety switch checks good with a continuity test.
Expert:  Dan replied 6 months ago.
Hi, It's Dan. Let me know where we are with this. I will see if I can find our old question as well.
Customer: replied 6 months ago.
No controls on boom. Everything else works. Safety switch is good. Nothing in fluid.
Expert:  Dan replied 6 months ago.
Have you checked the boom potentiometer and wiring harness yet? These machines will lock out the boom or arm function sometimes if they go bad , there's harness trouble, or they are out of adjustment or damaged.
Customer: replied 6 months ago.
I need to know the parameters of checking the pots. What each of the three pins are, there is a lineup mark on the pot, and it seems to be a dead spot. I need parameters.
Expert:  Dan replied 6 months ago.
Manuals for this model are scarce as this is considered a grey market machine in the US. I have a manual for a 128uu-2 which uses boom potentiometers and arm potentiometers for the cab protect system. Try disconnecting them one at a time to see if the boom begins to respond. Also with the connector disconnected try a resistance check and mover the potentiometer while monitoring the readings to be sure they increase and decrease, etc. Check for an open circuit. The 128uu-2 has a switch RH console below the seat to disable this function in an emergency. Check for a switch in the cab. I did locate a source that claims to have the full service book for under 35. Here is the link.
Customer: replied 6 months ago.
I am an industrial electrician, so i understand how pots work, i just dont know the pinout.
Expert:  Dan replied 6 months ago.
That manual will have the schematics but since this is black market I dont have the schematic for this model. I doubt it is the same pot but I can see if maybe the part numbers match...
Expert:  Dan replied 6 months ago.
Hi, Did you get this resolved? If not let me know as there might be another expert that has those schematics and test information
Expert:  Dan replied 6 months ago.
Grey market machines are tough to get service information for unfortunately.
Customer: replied 6 months ago.
Still not working
Expert:  Dan replied 6 months ago.
By chance did you reach out to the person in the link I posted to see if they still have the manual for sale for this model? They are very tough to come by in the US. Otherwise I would be sharing test info for other US model machines and the specs likely will not match.
Expert:  Dan replied 6 months ago.
Ill opt out in case another expert has this machines manual for those test values and pin outs.
Customer: replied 6 months ago.
Dan,Just wanted to let you know what I found. Thought it may help on the next one. The front potentiometer was bad in one spot. I bought a radio shack 5k ohm and put it there to prove my prognosis. I have ordered a new Komatsu pot. the controls started working but was erratic. we pulled the console off the machine (where the start switch is) and flipped it upside down to take a look. it started working. we went through and reconnected all pin/plug connectors and checked for loose wires. As of right now this machine is operating. Thanks for your help.

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