Workcentre 7855 toner sensor inaccurate - can't use the machine

[MaestroLM]

I have a second-hand Xerox Workcentre 7855 that I treat with loving care; it's the heart of my small non-profit. As it's second hand, I can get no support from Xerox, and we're in a very remote area far from qualified tech support.

My machine began claiming the yellow toner cartridge was empty and needed to be replaced - but it was nearly full. I replaced it; same message. I completely cleaned out the channel and sensor and then tried a third cartridge: same result. Today I bought a FOURTH toner and - no good. I've swapped the toner sensor with that of the magenta toner and I still get the same result for the yellow toner.

I'm getting desperate. I've actually used a hack to reset all the toners to 100% but STILL the yellow shows empty, despite the fact that hack worked for the other three.

HELP!!! I'm a desperate, disabled old guy who just needs to keep this thing alive and now - there's an element of time involved. ANY IDEAS? Thank you in advance...

[xcopytech]

Remove toner dispenser and check for broken auger

[MaestroLM]

xcopytech, my friend: you've done it again. I disassembled the machine, pulled out the (C,M,Y) dispense pipe assembly and you nailed it. The Y auger won't budge, and after I try to empty the yellow toner from that channel, I will see if I can get the auger moving. If not, one last question: could you please share with me the name of an online parts dealer for Xerox needs? I've been able to find most of what I need over the years from GMS, but they don't seem to have the assembly in stock. But most important: I can't thank you enough for helping out a non-tech retiree who's been forced to use his inquisitive mechanical/engineering curiosity to get to the bottom of things with this machine! You ARE the best, my friend!

UPDATE:

Unfortunately, that didn't seem to be the problem. I just finished taking the entire assembly out - and the yellow auger WAS stuck fast. Jammed in place by tons of old toner, which had compressed and eventually frozen the auger in place. Odd - because I only use OEM cartridges, and the exhaust for the yellow toner wasn't blocked. So - I was able to eventually dig out enough of the old toner from both ends that I could finally wiggle the auger loose and it's in perfect shape. Not broken - so I then cleaned everything out, reassembled the dispense pipe assembly, put the machine together and after the machine went through its warm-up: same problem. "Replace yellow toner." Toner sensor is perfectly in place, it's a brand-new OEM yellow cartridge, but the supplies display shows "0%" - just as it has been. I am completely flummoxed. Any ideas - in addition the auger thought, which WAS a great one? The toner cam motor seems okay, too -

[MaestroLM]

PLEASE - Does ANYONE have any ideas? YELLOW CARTRIDGE IS NEW, but the machine won't recognize it as full. I have tried 4 OEM cartridges and all get the same result: "Open front door, replace yellow toner.) I've cleaned out the dispense auger, the sensor has been swapped with another color, wiring all seems fine, I've tried resetting levels - and can with the other three toners, but NOT yellow. Therefore, machine refuses to make ANY copies or to print.

I'm desperate - I have a deadline for a non-profit and there are no alternative copy shops or printers anywhere. ANY IDEAS ARE WELCOME, PLEASE!

[stev0]

Hopefully this helps. I'm no expert but I'm guessing running the dC991 is just for it to re-register and clear the error.
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Adjustment 1. Enter the UI Diagnostic (CSE) Mode. 2. Select the Adjustments tab. 3. Select dC991 Tone Up/Tone Down. 4. For each color that is above or below target, enter a value between -99 and 99 into the row and select This value is the number of tone up or tone down cycles to be performed. Negative values increase the ATC Average; positive values decrease ATC Average. 5. Start on the UI. 6. Repeat as required until ATC Average matches ATC Target. If the measured (average) value cannot be set to the target, there is a problem in either the toner delivery system (Dispenser, low toner sensor, etc.), or in the TC detection circuitry.

[MaestroLM]

StevO - thanks very much. I'm trying to follow through but my tech level is that of an advanced idiot... I've been trying to figure out how to carry out this procedure via the CIS(?) but have yet to get to the specific modes you've limned. Hate to ask for more help, but could you walk me through the process if you have time to write it out as if aimed at a six-year-old's brain?!