laserjet m600 (602) fusing problems

[boscru]

hello all--new to the forum--not the business. i go back to the typewriter days

i have a customer w/ a 600. fuser was bad, replaced w/ a refurb from a reputable supplier i have been using for 25 years.

fuses fine on plain paper, but card stock is a problem. toner doesn't fuse properly. on the 42xx series i would just jack up the fuser temp. to fix.

n/a on the 600's that i can find. i do see i can change the resistance mode and the humidity mode.

card stock is fed through by-pass tray, but i can't change by-pass paper type to card stock. due to their store-wide o/s & software if i change it, it then pulls from tray 2.

national retailer, i've known i can't do this since i took on the customer 10+ years ago, however the temp change was a quick, easy fix on the older devices.

what is the resistance mode???

answer to this and any other thoughts appreciated

[Lance15]

RESISTANCE MODE
Set to Up to resolve print-quality issues caused by poor secondary transfer in low-humidity environments with resistive or rough surface media.

[boscru]

swapped the fuser. took care of it. just a bad rebuild, unusual for this supplier, but warranty covered it.