We have this 320 C and just a day or two ago the swing motion started cutting out intermittently, all the other motions are working just fine. When it won't swing we'll cycle it, turn the machine off and on, travel back and forth, and it'll start working again randomly. Not sure if this is a gear problem or maybe a solenoid, it has been starting to freeze at night here, so maybe an ice problem, I'm not sure. We did put a new set of throttle cables with the throttle position sensor box on recently, which needs to be tuned in still, as it doesn't throttle up all the way, and for some reason the auto idle only kicks down and not back up when I start using the controls again, instead I'll have to turn the knob on the dash for the throttle to kick back up again, this throttle box came from china, not from Cat, so I figure that's why, it was also an $800 difference in prices. I'm not sure if this could be related to the swing problem, I doubt it since we've had the latter problem for a few weeks which has been aggravating, but not nearly so much as not being able to swing for the last few days, any input would be greatly appreciated. Thanks
another thing to add is that once moving again the swing motion seems to be fine until going under a load or abruptly changing directions.
Cycling the machine on and off does indicate an electrical issue. Take a look at the swing brake solenoid to make sure that it's fully engaging and allowing the 600psi to release the brake. Also check your implement pressure switch and the powershift solenoids to make sure the signals are not consistent with the issue. Also, make sure you're getting full pilot signal to the swing spools and that the mains pump for that swing direction is stroking up.
My 2000 311b did the same thing it was the swing solenoid on the main valve body about a $50 fix