Construction and Road Equipment

Construction and road equipment repair questions? Ask a mechanic ASAP

Connect one-on-one with {0} who will answer your question

This answer was rated:

I have a komatsu pc28uu-2 with no down pressure on the

boom/bucket. Everything else works fine...
I have a komatsu pc28uu-2 with no down pressure on the boom/bucket. Everything else works fine. It always has the blinking red indicator light on. I have taken the connectors apart on all 3 sensors on the boom and they each are getting 5 volts to the sensor and the resistance varies from 1 to 5k ohms on each. Any suggestions?
Show More
Show Less
Ask Your Own Construction and Road Equipment Question
Answered in 2 days by:
8/11/2016
Mechanic: Dan, Technician replied 6 years ago
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 15,098
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
Verified

Hi Paul, My name is***** you still need help with this? If so please post your machine serial number and I will be glad to try to help.

Ask Your Own Construction and Road Equipment Question
Customer reply replied 6 years ago
Serial number 11132
Mechanic: Dan, Technician replied 6 years ago

Thanks for the info. If your have 5 volts to the boom sensors, the voltage coming back will be between 0 and 5. If the wiring harness and sensors are good which is the most common cause then the next step is to check for a hydraulic issue. Check the oil and filter condition for fine metal or debris indicating a mechanical problem. Let me know the results and if we need to dig deeper.

Ask Your Own Construction and Road Equipment Question
Customer reply replied 6 years ago
The sensors do not have a dead spot and wiring is fine. I moved on the switched the two hyd hoses going to boom cylinder (just switched places of the two) . The boom lowered with pressure and would not raise. This tells me cyl is good. Then I switched the pilot pressure lines going to the boom valve and again it would lower and not raise. I beleive this tells me the control stick and pilot lines are good . I beleive now the boom valve is bad, do you argee and what's the next move as far as disassemble / cleaning/ inspection/ etc
Customer reply replied 6 years ago
I remove both hoses to the boom cylinder and the one that goes to the piston side (raise) always has fluid pouring out of it. I then moved and the controller to raise the bucket and same amount of fluid kept pouring out. Does this boom control valve have its own relief and if so how do you test ?
Mechanic: Dan, Technician replied 6 years ago

For the reliefs You will either need test gauges to verify the pressures are in OEM specs in the shop manual and also remove them to visually inspect for debris or damaged o rings causing them to stick open and bypass pressure. Click on this link to access the parts manual online to help in identifying your components.

Parts book

Ask Your Own Construction and Road Equipment Question
Customer reply replied 6 years ago
Do you have a service manual for this machine ( ref oem specs) or can you provide a more details description of how to do the non visual (like look for something obviously wrong) checks?
Mechanic: Dan, Technician replied 6 years ago

Hi Paul, I do not have the service book for the dash 2 and your serial number but what you are looking for is for metal/debris in the filter and in the relief valve cartridges for the control valve. Remove the complete assemblies and do not change the adjustment settings on the top adjusting screws. Look for damaged o rings ans for metal/debris causing them to stick open. If the filter has a lot of fine metal it is and indication of a pump or component failure occurring. Use the parts book link to Identify your valves and locations. Let me know

Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 15,098
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
Verified
Dan and 87 other Construction and Road Equipment Specialists are ready to help you
Ask your own question now
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a mechanicLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Dan Your Own Question
Dan
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 15,098
15,098 Satisfied Customers
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.

Dan is online now

Related Construction and Road Equipment Questions
Day 1 machine started right up ran/operated fine. Day 2
Day 1 machine started right up ran/operated fine. Day 2 machine started right up ran fine but boom/bucket joystick didnt operate. I could drive the machine. Day 3 machine took 25 sec cranking to get s… read more
Curtis B.
Curtis B.
Technician
Associate Degree
2,324 satisfied customers
Tvwon't allow bucket to raise 5511 to 5512 code. 2018 case
Tv(###) ###-####won't allow bucket to raise 5511 to 5512 code … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
I have a Komatsu PC 75 uu also. I took the articulating ram
I have a Komatsu PC 75 uu also. I took the articulating ram off and installed a solid rod in its place. Now it won't boom up and I have had this problem before. I removed the articulating ram, so I do… read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
LW130 tc loader. Hydraulic lock out light flashes boom and
hydraulic lock out light flashes boom and bucket will not move … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
My boom bogs down, and my pump does not rev up... But this
My boom bogs down, and my pump does not rev up... But this only happens with the boom control,,, the bucket, the arm extension and rotation is all ok, … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
I own a 1996 Samsung Se 280 excavator and basically my issue
Hi, I own a 1996 Samsung Se 280 excavator and basically my issue is everything is working hydraulic wise except for the stick. The main boom with the two hydraulic jacks works fine and the bucket move… read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
I cannot unlock my foot pedals on my 2001 new holland skid
I cannot unlock my foot pedals on my 2001 new holland skid loader i just bought … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
Failed seat sensor on 96 bobcat 753. Looking for way to wire
Failed seat sensor on 96 bobcat 753. Looking for way to wire in a bypass. Have variable resistors, diodes, etc. on hand … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
L have a cat skid steer 226b3. I have a drive problem.
Hi , l have a cat skid steer 226b3 . I have a drive problem . … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
I have just bought a second hand Komatsu PC78-6EO model
Hello, I have just bought a second hand Komatsu PC78-6EO model excavator. There is an error code E40 which indicates a boom sensor is out … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
I have a cat 299D XHP the operator warning light flashes and
I have a cat 299D XHP the operator warning light flashes and the Air Filter light illuminates when I attempt to move the boom up/down. I changed filters all lights are off until i attempt to move the … read more
catmastertech
catmastertech
Field service technician
Vocational, Technical or Trade Scho
1,325 satisfied customers
I have a link belt 3400q that stalls when the bucket is
I have a link belt 3400q that stalls when the bucket is opened or closed … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
Dan tried to help a few weeks back and nothing has worked JA: We'll d
dan tried to help a few weeks back and nothing has worked … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
Komatsu pc28uu boom joysticks has no control. theres a light
komatsu pc28uu boom joysticks has no control. theres a light on the dash that's in Japanese that's on. everything else works … read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
Komatsu WB140-2 #F110xx Backhoe Loader |=| Problem: Starter
Komatsu WB140-2 #F110xx Backhoe Loader |=| Problem: Starter won't turn over. |=| Background: When I short relay K01 (Starting Relay) pins 30 and 87, then it starts just fine using ignition key. The vo… read more
Dan
Dan
Technician
Auto Mechanics 1&2/diesel mech
15,098 satisfied customers
I have an issues with my Cat 232B2 skid steer where the work
I have an issues with my Cat 232B2 skid steer where the work tool and arms hydraulics (right joystick) are are not operating properly.… read more
catmastertech
catmastertech
Field service technician
Vocational, Technical or Trade Scho
1,325 satisfied customers
I have a E120b catapillar excavator and motor was almost
I have a E120b catapillar excavator and motor was almost stalling when lifting boom I have replaced 4 relief valves had hydronic pump reconditioned 130 hours ago ,have recently replaced hydronic oil a… read more
catmastertech
catmastertech
Field service technician
Vocational, Technical or Trade Scho
1,325 satisfied customers
I have a CAT-226 Skid steer.It starts, drives fine, but
I have a CAT-226 Skid steer. It starts, drives fine, but the bucket has no hydraulics at all. Seat belt light flashes, and bucket stopped moving.… read more
catmastertech
catmastertech
Field service technician
Vocational, Technical or Trade Scho
1,325 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Curtis B.

Curtis B.

Technician

2,324 satisfied customers

Technican turned service manager with multiple lines of equipment and rental units.

Wayne

Wayne

Journeyman

1,298 satisfied customers

worked on many road graders, Bull dozers , skid steers, Rollers

Cat Man

Cat Man

Cat Engine Expert

578 satisfied customers

I am ASE Master Certified.

dieseldan55

dieseldan55

Mechanic

299 satisfied customers

Road Mechanic for Volvo Construction Equipment.

Chris (aka- Moose)

Chris (aka- Moose)

Technician

85 satisfied customers

24 years of experience diagnosing & repairing

Steve

Steve

Mechanic

42 satisfied customers

Heavy Equipment Mechanic for 25 years

JBFixxer

JBFixxer

Mechanic

22 satisfied customers

16+ years experience, hydraulics,hydrostatics, engines, fuel injection systems. And everything in between.

< Previous | Next >

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x