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catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 2294
Experience:  Field service technician for CAT 19 years.
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I have a caterpillar 322b excavator in periodically all the

Customer Question

I have a caterpillar 322b excavator in periodically all the hydraulics shut down until I shut it off and let it cool for 10 minutes then it will operate normally until something kicks out again is there a relay for the operator safety switch or something that I could look at to try to solve this problem
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 year ago.


I haven't seen this happen to a B model but, I did see a C model have the lockout solenoid stop the machine like this.

The relays have been extra reliable, I have never replaced the ones that work the solenoids.

If you are loosing power to all the cab, then I would say it is the main relay going bad.

Since it is just the hydraulic, I would believe the lockout solenoid should be replaced first.

If this is not the issue, you will need to access the monitor to find the active fault code when the problem appears.

This solenoid is directly under the cab, access through the bottom plates. I think it will be the second from the front plate.

Look for a valve with several lines connected to it and a single solenoid. It is part number,(###) ###-#### ***** has changed numbers a few times but, it is large enough you will see it easily.

If you need further help, please post the full machine serial number with your request.

Customer: replied 1 year ago.
I am losing complete power to the cab the key will turn off but will not turn back on until whatever it is cools down there is a clicking noise when it turns off like a relay kicking out but I cannot find it yet could you tell me where that relay is that you had mentioned in your answer please
Customer: replied 1 year ago.
I have found the solenoid valve that is clicking off when this machine shuts down but I cannot find a relay that goes to it
Customer: replied 1 year ago.
the serial number on this machine is 2ES 00290
Expert:  catmastertech replied 1 year ago.

Thanks for the serial number. I will attach a parts page that covers your machine.

The large relay in the center of the panel is the main cab relay. ( I assume this is the solenoid you are referring.)

Cat calls it a magnet switch, (of course they have their own name for it!) it is item number 10 (3T-0376) on the list and it callout D in the image.

You need to check the small wires to see if they are correct before replacing the switch.

The black wire is a common ground and the yellow wire is from the key switch when the key is on. Verify the ground is good and you have voltage from the key switch when the switch fails. If you do have power and the switch is not closing, then it is the problem. (It should get hot when in use.) Check power supply on the red wires too. They are from the battery main breaker and the purple wire is the power supply to the cab electrical. When the key is on, the switch closes and sends power from the red wires to the purple wire.

NOTE: I have seen one machine have loose wires on the key switch cause this same issue. That is why you should verify the yellow wire is sending power to the switch first.

If you need more help, please let me know. I will be glad to help all I can.

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