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my customer has a cat 312b sn 8jr012241 it will swing around…

my customer has a cat...
my customer has a cat 312b sn 8jr012241 it will swing around fast but when you swing slowly it locks down the swing every certain clock position. we removed the swing drive motor and all gears look in great shape we are trying to remove the base of the swing drive assembly and it looks like a dowel pin or possibly a bolt from underneath as we are checking to see if the shaft is bent we need to know how to remove the base assembly or if we have to or not. I was thinking about the problem and we have changed the hydraulic filters and all fluid and keep getting a restricted filter light, could this be caused by a malfunctioning solenoid and if so what are the resistance values for the solenoids
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Answered in 4 hours by:
8/9/2013
Mechanic: catmastertech, Technician replied 9 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,969
Experience: Field service technician for CAT 19 years.
Verified
Dowel pin only, no bolts on the bottom. (No access anywhere)
Most have threaded holes for forcing screws on opposite sides, one is usually near the dowel.
Never seen a shaft get bent. Rare to see one break. Operator has to really abuse the machine to break this gear. Most models have a cover plate in the front of the carbody to view the bearing gear teeth. It is always mounted between the boom cylinders. This is the easiest way to inspect for damage. Any problem on the swing gear will leave marks on the swing bearing teeth.
Hydraulic filter has a reset button on the bottom of the housing. If decal is still on the switch, it will look like the off button on your PC. ( O with a I in the middle)
Have you tried operating the swing with the motor out of the drive gear?
How about pushing the machine with the motor out? It will take some force to start it moving but, should move freely. If it is binding, you will feel it will pushing it around.
Stop and start at slow speeds could be the return flow check valve. This will usually make the boom down and stick in, jerky at times also.
Yes, it has a swing solenoid. A quick test is to switch the backup switch into Manual (override) and retest for problem. This will place a constant current on the solenoid and hold the brake off if all the wiring is good to the solenoid.
If this is the case, I suspect you have a failing implement pressure switch.(NNN) NNN-NNNNis the part number for both the travel and implement pressure switches. This unit also pressure switch on the travel control. Try applying a light pressure to the travel pedal and the swing problem should go away.
These pressure switches are located on the main valve. Look in the center and you will find two switches mounted on tee fittings. Unplug one and retest to see if if work the swing brake from travel pressure or implement pressure.
(By design, when the implement or travel controls are operated, the swing brake releases. The brake will remain off for 6 seconds after the controls are centered)
When in backup mode swing brake is always off. An option for a manual swing brake release switch is on the right console.
The brake solenoid should read 32 ohms if cool.

If you need more help on this, please feel free to ask. I will be glad to help.
If you find something different, please detail the results of the above testing and what you have done so far.
Thanks, Donnie
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,969
Experience: Field service technician for CAT 19 years.
Verified
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Customer reply replied 9 years ago

I have replaced the swing brake solenoid after I assembled everything I ran the machine for half hour and it started hanging up on swing again, I went out this morning and the machine was cooled off,but the swing was still hanging up really bad and it was grunting/growling in swing mode , is it possible that the actual brakes in the swing motor are broken?

I went out there and unplugged pressure switch F at the main valve and that seems to make the problem go away but the motor throttles down a little when in swing mode ,I have ordered a pressure switch from cat ,but I do not know which functions the two switches perform, there are only two switches at this location and instead of ordering two I would like to know which one to replace first so I am not playing the guessing game. Thank you , XXXXX XXXXX

Mechanic: catmastertech, Technician replied 9 years ago
I am thinking it will be the one on the left side of the machine. (To your right when facing the valve.)
Look for the switch with the purple and black wire. The other switch should be green and black.

Did you try the jumper wire? (to bypass the switch)

Did you try the backup mode? ( to override the switches)

Did you try to lightly press the travel pedal to see if the brake would release? (to trick the ecm)

Did you try unplugging the other switch? (to isolate the problem)

When the switch is unplugged, the brake should not release because it does not know the implement is working. This will also prevent the AEC (Auto Engine Control) increasing the engine speed.

Remember, the pressure switches will signal the ecm the implement or travel is working and to release the swing brake and increase engine speed.
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Customer reply replied 9 years ago

had to keep flipping backup mode switch to keep rotating,just had switch on right of valve (looking at it from front, the switch on right) unplugged only and adjusted swing brake solenoid in then out until I felt the least spring pressure and it was swinging about normally except for the throttle not coming up like normal. after this I did not have to go into backup mode. Switch should be arriving today from cat. Thanks, XXXXX XXXXX my phone is eight zero three five three two six three five two (Tom's Auto)

Mechanic: catmastertech, Technician replied 9 years ago
Ok, thanks for the update. If you need more help, please let me know.

NOTE: Please do not post personal information on this site. It is open to public viewing at all times. Everyone can see all the information you post.
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Category: Construction and Road Equipment
Satisfied Customers: 3,969
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