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Thanks for the help. My Komatsu excavator PC75UU-1 has lost…

Customer Question
Thanks for the help...

Thanks for the help. My Komatsu excavator PC75UU-1 has lost the swing function and the dipper, ie, everything controlled by the left joy stick. Both functions were lost by degree. For 3 or 4 days, the swing would work for about 45 minutes, then lock up at about 45 degrees from straight forward. I would shut the machine down and by next morning it would work again for a while. Eventually it locked up straight ahead and would no longer respond. The dipper function worked in one direction but not the other. Now it works in neither. In order tor replace the throttle control cable I removed the steel box seat support and found that several wires had been damaged by mice, and I have repaired them, but with no improvement. Also, I removed the rectangular floor panel revealing two rectangular electrical devices. Thanks for any help. Alexis Moser (###) ###-####***@******.***

Mechanic's Assistant: What is the complete model and serial number of your machine?

The Model is PC75UU-1. I don't have the serial number, but will go out to the woods to try to find it. I will need to shut down the computer; can I reach you to continue? Thanks Alexis

Mechanic's Assistant: Is there anything else the Equipment Mechanic should know before I connect you? Rest assured that they'll be able to help you.

I think I included all the relevant information and history of the failure. Alexis

Submitted: 2 months ago.Category: Construction and Road Equipment
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Answered in 21 hours by:
9/26/2022
Mechanic: Dan, Technician replied 2 months ago
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 15,116
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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Hi my name is***** to hear you are having these troubles with this. Give me some time to review your information and follow up with my suggestions.

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Customer reply replied 2 months ago
Thanks..please use email for long mesages alexis hiramsky gmail com
Mechanic: Dan, Technician replied 2 months ago

Sorry to hear you’re having these troubles with this machine. Check for any battery or charging system related problems that would cause voltage supply related issues as well as any faulty fuses or relays. Replace any damaged wiring within the wiring harness that would cause a short or open circuit within the wiring or connector pins. Check your left hand console  safety circuit for proper operation that was shut out your hydraulics.replace your hydraulic filter for the purpose of inspecting the existing filter internally for what looks like find metal or glitter within the oil and filter confirming hydraulic component or pump related failure existing on this machine as well as system contamination that would need to be investigated further. Check inside your control valve spools and your relief valve cartridges for the circuits that are having troubles for any damage or trash and debris that would cause the valves to stick in malfunction. If all of this checks out OK you will want to have your circuit pressures checked and verified whether or not they are within the factory specifications for your equipment model and serial number service book. Verify that the hydraulic pumps are turning at engine rpm and that there are no troubles with the hydraulic pump drive coupling between the engine and pump assembly. I hope you find this information helpful.Click on this link below for a very reasonably priced service book for this model machine available for download. There is never a great replacement or substitute from having the actual service book on hand.

https://therepairmanual.com/komatsu/komatsu-pc75uu-1-excavator-service-manual/

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Dan
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Category: Construction and Road Equipment
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