86 Paper Jam z2100

[chrisonline209]

I have a paper jam fault after changing the belt.  The belt is installed correctly and is oem. When I put it back together I messed up the trailing edge cables.  I bought cheap ones from Amazon.  Fired it up and had the fault. Talked with Tim at LPS computers, great guy. He recommended and I did change the encoder strip. Same problem. Yes the the encoder strip is metal side upwards.  Still have the same problem and so Tim recommended I change the belt motor. I did, no help same problem.  When initiating the carriage moves about a centimeter to the left, and then right back, and faults out. Want to note that to me, the carriage makes noise when I move it by hand and since I never moved it by hand before, I am not sure how much drag I should feel when I move it.  There is definetly tension on it and you can hear it move.  I do not know the next step.  Should I go backwards and think that I got cheap trailing edge cables and maybe they are not giving the carriage the right signal.  Could this be a trailing edge cable issue?  encoder strip sensor issue?   I have no idea as of this point. 

[Kuroi_Kenshi]

Hi @chrisonline209.,

Welcome to the HP Support Community!

Thanks for reaching out!

We're thrilled to have the opportunity to assist you and provide a solution.

I understand your HP DesignJet Z2100 showing an 86 paper-jam error after replacing the carriage belt, with the carriage moving slightly during initialization and then faulting. Let’s go through the most likely causes based on what you’ve already replaced.

The 86 error on a DesignJet Z-series is usually a carriage-motion detection fault, not a paper-feed problem. Since the issue started after belt replacement, the focus should stay on carriage sensing and cable communication.

Check the trailing cable installation again
The carriage trailing cable (flex cable) is critical for encoder-sensor communication.
If the cable is not fully seated, slightly twisted, or electrically inconsistent, the carriage will move briefly and then stop with an 86 error.
Aftermarket trailing cables can sometimes cause this exact behavior.

Inspect the encoder-strip sensor on the carriage
Even if the encoder strip is installed correctly (metal side up), the sensor inside the carriage may not be aligned with the strip.
Make sure the strip passes cleanly through the encoder sensor slot and is not rubbing or offset.

Check carriage movement resistance (important)
With power off, gently slide the carriage left and right.
You should feel smooth, even resistance from the belt and motor, not grinding or sticking.
Noise or uneven drag can indicate:

Belt tension too tight

Carriage rod needing lubrication

Encoder strip rubbing

Belt not seated correctly on pulleys

Verify belt routing and pulley seating
Even with an OEM belt, confirm:

Belt teeth are fully seated on the carriage motor pulley

Belt is not twisted

Belt tensioner is installed correctly
Incorrect belt tension can trigger carriage-motion faults immediately at startup.

Reseat all carriage-related connectors on the main board
Open the electronics area and reseat:

Trailing cable connection

Carriage-motor connector

Encoder-sensor connector (if accessible)
Poor contact here can produce the exact “moves 1 cm then faults” behavior.

I hope this helps.

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Best regards,

[Repairatrooper]

The encoder strip does not go metal side up. Metal side is down. Image from service manual.

[chrisonline209]

I am confused. LPS Computers says the metal strip goes up, but the book says down???

[chrisonline209]

I do hear noise when I move the carriage left and right. If I tilt the front of the carriage up, kind of lift up on it, the noise goes away.  My plan is to order an oem  leading edge cable and replace the amazon model I got. Did I mention that my star  assembly motor apparently is not working now also and that I believe it is in the up position. Everything was working fine until I changed the belt and messed up the trailing edge wires.   One of the commenters says the metal edge of the encoder strip is supposed to be down, not up.  Please clarify.

[Repairatrooper]

The picture is from the actual service manual. I have also personally worked on a lot of these and have NEVER seen one with the metal strip up. Not even sure how you got it to tension properly or did the strip you buy come without the right side metal retainer and you transferred it from the other one. Only take you fifteen minutes to swap it and see if it works properly.

[chrisonline209]

I will give it a shot.  Also want to note that my starmotor is not activating, maybe it can't get to that point in initialization and it is in up position.

[chrisonline209]

Thank you so much for your reply. Tonight, based on information on comments, I turned flipped my encoder strip so that the metal portion is down and the rubber portion is up.  No help.  I think I hear and feel resistance and so if i tilt the front of the carriage upwards it goes away.  If I look under the carriage and try to see where the resistance is coming from, it looks like the back bottom portion is rubbing on what I guess would be the star wheel assembly.  I have reseated all electrical connections around trailing edge board on left of machine.  I think my starwheel is in the up position.  My starwheel motor does not spin during initalizion because I do not see those geers move, but maybe it is faulting out prior to voltage being sent to that motor.   My question at this point is , Is it likely I got cheap trailing edge cables from Amazon and I need to buy OEM? 

[chrisonline209]

Thank you so much for your reply. Tonight, based on information on  your advise and comments, I turned flipped my encoder strip so that the metal portion is down and the rubber portion is up.  No help.  I think I hear and feel resistance and so if i tilt the front of the carriage upwards it goes away.  If I look under the carriage and try to see where the resistance is coming from, it looks like the back bottom portion is rubbing on what I guess would be the star wheel assembly.  I have reseated all electrical connections around trailing edge board on left of machine.  I think my starwheel is in the up position.  My starwheel motor does not spin during initalizion because I do not see those geers move, but maybe it is faulting out prior to voltage being sent to that motor.   My question at this point is , Is it likely I got cheap trailing edge cables from Amazon and I need to buy OEM? 

[Repairatrooper]

You state that if you tilt the printhead back it moves. This happens of you fail to install the top bushing on the carriage properly, easy to break if you miss it when inserting the printhead assembly into the carriage.