I have a 320c Cat excavator which has been standing for a…

Hey, sorry to hear you are having these problems. I know that can be frustrating. Hopefully, we can get you back to work quickly. I see no one could help you earlier, and I hope this is not too late to be helpful. Please note that I am not set up for phone calls, you can ignore the site pop-ups. We can post to this chat as much as you like to work through this issue. All experts are not employees, and we work from home in our spare time to answer questions.

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Try using the backup mode switch. Place the switch into the manual or backup mode and see if the swing brake will release. If it does, the issue may be the pressure switches on the main control valve. This will also have some effect on the throttle AEC and it may not idle up at times.

If it does not release the swing brake, the issue may be the swing brake solenoid on the pilot manifold has failed or is not receiving power.

The swing brake will be switched off when the ECM controller receives a switch input signal from the main control valve that indicates the implements are being used. This circuit passes through the backup mode switch and when you move the switch to manual backup mode, it will bypass the ECM control and send power to the solenoid directly and release the brake. The pilot manifold has three solenoids. One is on the end by the small accumulator bulb and is for the hydraulic lockout solenoid, the middle one is often the swing brake solenoid and the end one is for the two-speed travel control solenoid. Usually, these are all the same part and you could swap the travel solenoid with the swing brake solenoid to see if the corrects the problem.

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Thanks again, Don

CATMASTERTECH