ir105 jams on 4 or more duplex copies

[PJFixIt]

Copier is showing jam code 010F (PS12 sensor) with 4 or more duplex copies. One sided copies - no problem at all. In duplex mode, 1 copy - no problem, 2 copies - no problem, 3 copies - no problem but 4 or more copies it jams every time - one copy comes out of the finisher but the other 3 are stacked under the fuser rollers with leading paper halfway under the roller. Seems to me that the jam code displayed (duplexing reversal sensor PS12) is nowhere near where the paper is stuck. I checked the wiring, sensor checks all OK. What puzzles me is - no issues with 1,2,3 copies? If any one can shed some light, I'd appreciate it. Thanks in advance.

[teckat]

Check the operation of PS12 and the Sensor Support Plate.
If the support plate or the Upper Reversing Guide is bent or damaged, it may cause a problem with the paper activating PS12. The Sensor Support Plate is mounted to the the bottom of the Upper Reversing Guide.

[PJFixIt]

Thanks for your response. I checked the SL12 and mounting, don't see any issue there. Investigating further, when 4 or more 2-sided copies are requested, this is what happens. 1st copy comes out with both sides printed. the 2nd page that comes out of finisher is actually sheet no. 4 with one side printed (should have gone through duplex unit but never got there). It gets kicked out instead and jam happens. sheet 2 ,3 have gone through duplex unit but were stuck near fixing rollers due to the jam. SL12 never saw the sheet #4 but was expecting it, thus reporting as a jam 010F. Could actual problem be at internal/external delivery area like SL3 solenoid or something else? I appreciate any input.

[PJFixIt]

Fixed it. The problem was SL3 solenoid at the bottom of fixing unit that operates the internal/external delivery flapper. Replaced the solenoid and it took care the problem. PS12 duplex sensor thinks there is a jam as it expected the page 4 for back side printing but that page got kicked out due to flapper not working correctly.

[teckat]

Fixed it. The problem was SL3 solenoid at the bottom of fixing unit that operates the internal/external delivery flapper. Replaced the solenoid and it took care the problem. PS12 duplex sensor thinks there is a jam as it expected the page 4 for back side printing but that page got kicked out due to flapper not working correctly.

Great observation.

Kudos 🍻