D-I-Y Repair Assistance Guide
HP 7100 Series Officejet Printers

Last Update: 5/09/2010

Error Messages & Reset Codes


Mechanical "door open" switching mechanism, located just behind the left front fascia.
Arrow points to the trigger contact pressed by the maintenance door when closed. (Shown here fully exposed with front left fascia removed)

Center, just below the red circle and behind the red/black wires, is the CMOS battery.


If you have an HP Printer, chances are at one time or another you're going to see this message. That's not a slam against HP; while I won't buy another HP PC, I love their printers and own 8 or 9 of them. What I mean to say is that for some reason HP seems to have chosen to make "Carriage Jam" a sort of catch-all error message. Who knows, maybe the designers just liked the way it rolls off the tongue, maybe they couldn't think up any more appealing titles, or perhaps to limit memory used for processing added variables. Or maybe it's because there's a wide range of malfunctions & glitches the printer will interpret as a carriage jam, and there are. So when this error shows don't immediately assume the worst, and whatever you do don't start yanking parts around, especially not the carriage, because the trouble is almost never a true 'carriage jam.'

Certain my list does not yet cover all the causes, here are the ones I know of presently:

Items like the first 2 with some frequency, can result in the last one; a broken part. Here's why: the encoder strip is part of the system tracking and guiding the position of the carriage, often passing through the narrow channel of a sensor on the back of the carriage which reports count of the bar-code type lines or metallic punch-outs of the encoder strip, letting the system know where the carriage is at all times. If the encoder strip becomes coated sufficiently with atomized ink or dust, the sensor will eventually be unable to read the position. One of the actions this can apparently trigger is a very rapid recoil of the carriage to one end of the gantry rail, and minus it's guidance the carriage doesn't stop before slamming into the end rail mount.

When needed, clean your encoder strip (in place) using a dampened soft cloth, carefully passing the strip through your fingertips to clean both sides without pinching or binding the strip. To have access to the entire length, open the maintenance door so that the carriage is triggered to move center as if replacing a cartridge, leaving the door open while disconnecting the power. In nearly all cases, careful movement by hand of the carriage when it is out in printing bay is perfectly fine & allows for complete cleaning of the encoder strip and the gantry.

Wipe down the gantry with a dry or very lightly dampened cloth followed by a dry one. The rail is clean when it feels slippery and can be wiped with a white cloth without sign of dirt. On squeaky or older, heavy-use machines, spray a small amount of a silicone spray on a cloth and wipe down the rail, but leave no visible coating. Do not use WD-40 or Armor-all!

Any time there's been a problem & you find need to manually move or test the freedom of the printer carriage, you can avoid possibly causing or adding to damages by following this simple rule: if it doesn't readily move, stop; today's little plastic parts don't react well to use of force.

More to come soon....

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