MX4111 Duplex jamming

[harps05]

Hey Folks,

Customer has a MX4111 which is jamming during duplex. The thing is it seems to be fine while doing a single duplex page. But if it does more than 1 it seems to make a strange noise as if something is binding up (under heavy load, almost like one of the drums has a flipped blade). The result is a page halfway out the fuser or sometimes just before the fuser entrance and the remaining page in the duplex area. There doesn't seem to be any moisture in the paper and no curling. Single sided pages work fine without any problems at all.

I've checked the duplex sensors and replaced APPD1 and APPD2. Updated the firmware. Ran motor and clutch tests, will all seemingly normal. Checked drums, transfer etc. Even swapped out the fuser.

The fact it will do multiple single sided jobs and single duplex jobs, troublefree, has me stumped.

Any suggestions??

[ZOOTECH]

I had the duplex motor intermittently run backwards causing the same symptoms.