PC120-6 swing break will not release

[Dunderhead]

Hey guys, I have 120-6 that the swing break will not release on. I can operate with the override switch on.

With the override switch off and the brake turned on…I can sometimes get it to unlock for a brief second by turning while switching the brake switch off.

I replaced the top solenoid in the tree next to the pump and no change. I was told that is the swing solenoid.

I am at a loss as to what to do next. Any suggestions? Thanks in advance!!

 

[funwithfuel]

The Komatsu unlike other brands gives you the option of locking the swing. Most others don't give you that option. That is how it's designed. It's not an override to release, it's override to lock. Release should occur naturally every time you move the stick.

 

[Dunderhead]

The Komatsu unlike other brands gives you the option of locking the swing. Most others don't give you that option. That is how it's designed. It's not an override to release, it's override to lock. Release should occur naturally every time you move the stick.

there is an override toggle switch hidden inside the fuse box. When you flip the switch I think it bypasses the solenoid and allows the machine to spin.

 

[funwithfuel]

I was under the impression you were referring to the swing brake switch. I'm guessing you're losing signal from the swing pressure sensor. Can you access the service mode. JohnC has put together some terrific tutorials on YouTube to help you. Once inside service, you can monitor swing PPC or pilot pressure control. Odds are, it won't change.

 

[Dunderhead]

Than you!

 

[Dunderhead]

Would anyone happen to have the service manual for this machine?

 

[Dunderhead]

I was under the impression you were referring to the swing brake switch. I'm guessing you're losing signal from the swing pressure sensor. Can you access the service mode. JohnC has put together some terrific tutorials on YouTube to help you. Once inside service, you can monitor swing PPC or pilot pressure control. Odds are, it won't change.

I do not think i can access the service mode....

 

[LACHAU]

I do not think i can access the service mode....

It's easy to access the service mode.

 

[LACHAU]

Would anyone happen to have the service manual for this machine?

I can give you the shop manual, but PC120-6 has many manuals depending on their serial number.
Please show me your machine serial number so I can send you exactly the shop manual.

 

[Dunderhead]

Thank you so much!!!

 

[LACHAU]

Here you are.
Good luck.

PC120-6 shop manual

 

[Dunderhead]

Here you are.
Good luck.

PC120-6 shop manual

I cant thank you enough!!

 

[LACHAU]

You are both right!
The Komatsu PC100-6 has 2 switches that affect the "SWING BRAKE" system.
One switch is called "swing lock switch", and the other is called "swing lock override switch".

 

[Dunderhead]

I’m hoping to tackle it Friday.

if I am reading this correctly the swing brake solenoid valve is the 4th down on the tree? The local machine shop told me it was on the top?

 

[Dunderhead]

 

[LACHAU]

I’m hoping to tackle it Friday.

if I am reading this correctly the swing brake solenoid valve is the 4th down on the tree? The local machine shop told me it was on the top?

You are right.
"The swing brake solenoid valve" is 04th on the solenoid valve block.
By the way, I suggest you carefully check the swing brake solenoid valve's wiring and connector.

 

[LACHAU]

I hope to be helpful.

 

[Dunderhead]

Popped in a new solenoid and it worked!!!

Thank you!!!!