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I have a komatsu D66 crawler loader that operates very good…

I have a komatsu D66...
I have a komatsu D66 crawler loader that operates very good except when backing up it wants to do a left circle. I try to correct it with right peddle but it loses to much power and goes very very slow. Do you have any ideas?
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Answered in 9 minutes by:
2/23/2016
Mechanic: Dan, Technician replied 6 years ago
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 14,658
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***** is your serial number and also the complete model number?

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Customer reply replied 6 years ago
Komstsu D66S-1 s/n 1896. Year manuf 1991.
Mechanic: Dan, Technician replied 6 years ago

Thanks for the info. Check the transmission servo filter and screen for fine metal/debris indicating a potential pump or drive motor problem occurring. Click on this link for the filter and to access the parts catalog to help in identifying your components. Let me know the results

http://komatsupartsbook.com/#?k=!0!25!1306!21!55

Check for excessive case drain pressure in the drive motors and compare both sides. Disconnect the case drain, cap line, run a hose into a bucket and engage travel with track pinned between the chain and sprocket to prevent travel. Should be a low volume of oil. If it is under high volume or pressure that drive motor is bad.

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Customer reply replied 6 years ago
Hey Dan, I wanted to make sure that you knew the loader does go forward and steers straight and turns perfectly. It only has the problem of wanting to move to the left when in reverse.
Mechanic: Dan, Technician replied 6 years ago

thanks for the update.... Sounds like it is more of a control valve problem. You can access the breakdowns of the valves from the link I posted. Inspect the control valve and reliefs for metal/debris ans damaged o rings etc. Let me know if we need to dig deeper. Also still verify if there is signs of fine metal in the system.

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Customer reply replied 6 years ago
Dan, I am still in the process of going through your recommendations. I am not ready to close this help case.
Mechanic: Dan, Technician replied 6 years ago

Thanks for the update. Keep me posted.... The site I believe sends out automatic followups

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Customer reply replied 6 years ago
Dan, we are having trouble with a new problem with the loader and are not sure what the problem is. If I need to start a new conversation for additional pay please let me know.
The problem is that the loader will start and run but will not move. The guy working on it for me said the battery's were dead so he tried to jump start but ended up replacing both battery's. Now there is no lights showing up on the instrument panel and the loader will not move at all. I'm not sure if there is a safety switch that has gone bad of if I have some how lost power to the computer or panel or what? Please advise.
Mechanic: Dan, Technician replied 6 years ago

Hi You will need to open a new question for the new problem and I will be glad to help or if you prefer I may be able to send an additional services request for to cover the two questions and continue here if it is the same machine but different problem. Let me know

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Customer reply replied 6 years ago
If you can try to get the additional service request that would be nice but if not I will start a new question. Please let me know.
Thanks.
Mechanic: Dan, Technician replied 6 years ago

I sent over the proposed offer which would be the current question value doubled to cover both questions if you feel that is acceptable just accept the offer and we can continue here or you can rate this one and open your new question. Entirely up to you. Whichever is easier.

Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 14,658
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
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Customer reply replied 6 years ago
I have paid for the additional questions
Mechanic: Dan, Technician replied 6 years ago

Hi Steve. Thank you. Check to be sure the batteries are connected correctly for 24 volts and that the battery relay has not failed at the batteries as well as all wires connected. Also be sure all fuses and relays check good. If connected wrong you could only be getting 12 volts instead of 24.

Were there any sparks when the cables were being connected?

Here is how the batteries should be connected and also the battery relay is #6. When the key is on, power goes to the small wire on the relay and makes the connection between the two large posts for the battery cable. Check the connections and the relay. If this relay fails you will lose power to the cab

http://komatsupartsbook.com/#?k=!0!25!1306!1!13

Test power in and out of the keyswitch in all positions, Test the diodes shown in the harness, fuses, relays, and look for damaged wiring. Let me know the results and if we need to dig deeper. You may have a failed controller.

http://komatsupartsbook.com/#?k=!0!25!1306!1!12

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Customer reply replied 6 years ago
Hi Dan, thanks for the info. I just wanted to make sure you understood that the loader will start and does run good and will throttle up and down with no problems. The problem is that it will not move at all no forward, no reverse and no lights are lit up on the instrument display.
Customer reply replied 6 years ago
Still waiting on response from my last reply.
Mechanic: Dan, Technician replied 6 years ago

Hi Steve, I am not logged in all day on here and help on here in between jobs but will always respond back on my next available login.

Thanks for the clarification. Test for power and ground to the controller and instrument panel and test all fuses and relays. Inspect the harness connections to both the controller and instrument panel for damage or corrosion. Let me know the results.

If power and ground are confirmed and the harness tests good, it is looking like a faulty controller.

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Customer reply replied 6 years ago
Hi Dan, we just put in another controller in and the results are the same. Engine starts and runs good, loader works but still no lights in the instrument panel and the machine will not move forward or backward. In your last email you said to check the harness and to check for power and a ground. The problem I have is I do not know how to check to see if power is going in or coming out of the controller. There are two plugs that go into the controller with many wires and colors and color combinations. Please instruct me on how to check to see if i'm getting power to the controller or what should I do next.
Mechanic: Dan, Technician replied 6 years ago

Thanks for the update Steve. It is time to dig into the shop manual and have your guy run through the schematics for those tests as welll as test the pressures to see if they are in spec. I found a PDF manual for download for under 10 dollars. I figured that would be worth a shot at that price if it has all your testing and adjusting information, schematics, and specs... Click here for the link

Manual

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Dan
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 14,658
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Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.

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