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Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4290
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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My 1995 link-belt 3400quantum will reason two or three

Customer Question

My 1995 link-belt 3400quantum will for no reason two or three times a day lock and not unlock unless I sit with it running and keep pressing it on and off for ten or moor mins. This is the button on the left side with the heat fan control under the arm rest . This can happen anytime while working or just idle .i watch the display till it shows padlock gone then will run fine for days or 2 hours ,need the fix
Submitted: 5 months ago.
Category: Construction and Road Equipment
Expert:  Dan replied 5 months ago.

Hi my name is***** will be glad to help. Check the electrical switch and harness connected to that lever inside the console. Also if you swing the machine so the cab is in between the tracks you can remove the panel under the cab to verify the linkage is opening the pilot safety valve. Let me know

Customer: replied 5 months ago.
I have done those things the safety switch is clair ,no bad wire and the button is in place plunged in and no bad spots on harness
Expert:  Dan replied 5 months ago.

Ok, Do you have a digital multi meter to test Voltage and OHMs? If so, on the OHM scale and that switch unplugged, test continuity both open and closed to see if the switch is bad.

Expert:  Dan replied 5 months ago.

You can watch the meter with the lever in both positions to see if there is continuity in the closed position and no continuity in the open position

Customer: replied 5 months ago.
I did try that and I don't rember the numbers as it was a mouth ago but I did have it when closed and not when open .then finger that would be unless it was in the process of locking me out.
Expert:  Dan replied 5 months ago.

Yes the numbers should be close to zero for a good switch when closed (engaged or on) and then no reading at all when open ( lever up)

Expert:  Dan replied 5 months ago.

If that is ok then the problem could be in the valve itself for the pilot shutoff.

Customer: replied 5 months ago.
I did check out both of the switches and have ruled them out I was thinking it was some switch in the lines that tell if the air is up or in some kind of BCM
Customer: replied 5 months ago.
Or how can I rule out the computer in back of the seat?
Customer: replied 5 months ago.
Are we done ? Just check the two switches that I did already do ,I'm still at the start of the problem.
Expert:  Dan replied 5 months ago.

hold on... questions are getting mixed up on the site bare with me while I see what is going on

Expert:  Dan replied 5 months ago.

We can post back and forth as needed. I am not an employee of the site. I am a user just like you. I help on here in between jobs and as I am available. Even if there are delays in my response I will always reply back on my next available log in.

Expert:  Dan replied 5 months ago.

Are there any fault messages on the monitor panel? If the machine works fine once you get the pilot safety lever to recognize it is up and there are no other problems it is highly unlikely a controller problem. It is most likely a switch, harness, connector pin, or valve problem

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