Procolored L805 H71 Error Explained: APG (Auto Platen Gap) Failure, Causes, and Fix Options

Question

I'm using a Procolored L805 (Epson L805-based) printer and I'm seeing the H71 error. What does H71 mean, and what usually causes it?

Answer

What the H71 error means on a Procolored L805 / Epson L805

On the Procolored L805 (which is built on the Epson L805 platform), H71 generally points to an APG issue-the APG (Auto Platen Gap) unit is the mechanism that adjusts or confirms the gap between the printhead and the paper/media.

In simple terms: the printer is trying to "home" (initialize) the platen gap mechanism, but it can't confirm the correct position. This is why technicians often describe H71 as an:

• APG home-position seeking error

• APG sensor failure

• APG motor failure

• APG mechanism obstruction / foreign object detected

• Cable/FFC (flat-flex cable) disconnection related to APG sensing or movement

When the printer can't get a valid signal back from the APG sensor (or the APG can't physically move), it throws H71 to prevent head strikes and further damage.

The most common causes of H71

Here are the most frequent real-world reasons this shows up after normal use, maintenance, or reassembly:

1) APG sensor not detected (sensor loose, fallen off, or not seated)

This is extremely common-especially after working inside the printer. If the APG sensor is misaligned, knocked loose, or not seated correctly, the printer "can't see" the APG position.

Typical signs:

• Error appears immediately on startup.

• The printer attempts initialization, then stops with H71.

2) Foreign object or obstruction in the APG path

Even a tiny piece of media, dried ink chunk, torn film, or debris can prevent correct movement.

Common culprits:

• Paper scraps or vinyl slivers

• DTF film fragments

• Adhesive residue buildup

• Dried ink blobs around moving parts

If the mechanism can't reach home position, the printer assumes failure and triggers H71.

3) APG motor failure or gear slip

The APG mechanism relies on a motor and gear train. If the motor is weak, stalled, or a gear is cracked/skipping, the printer can't move the gap mechanism accurately.

Typical signs:

• Grinding/clicking during startup

• Intermittent H71 (sometimes it starts, sometimes it fails)

4) APG-related cable/FFC not fully seated

This is another very common one after service. A slightly unseated FFC ribbon cable or connector can cause the APG sensor signal to disappear.

What happens:

• Printer mechanically moves, but receives "no signal"

• Firmware interprets it as sensor failure → H71

5) Incorrect reassembly after maintenance

If parts were removed for cleaning, modification, or head work, the APG bracket/sensor alignment can be off by a small amount-enough to break the homing logic.

What you can usually check (high-level, non-invasive)

Because H71 is APG-related, the practical checks generally fall into two buckets: movement and sensor feedback.

Check for movement problems (obstruction/jam)

• Inspect the paper path and platen area for scraps, film pieces, or anything stuck.

• Look for anything that could physically stop the gap mechanism from moving.

Check for sensor/cable issues (no feedback)

• If the printer was recently opened or serviced, the odds are high that the APG sensor or its cable/FFC is not seated properly.

• A loose or partially inserted ribbon cable can look connected but still fail electrically.

Why H71 matters (and why the printer stops)

The platen gap is a safety-critical part of the system. If the printer can't confirm the APG position, it can't guarantee head clearance. Continuing to print could risk:

• Head strikes

• Media crashes

• Damaged printhead or carriage assembly

So the printer throws H71 to force a stop.

Printer troubleshooting can be a complicated affair because these problems are hands-on and often depend on what we find physically inside the unit. That's why we're not able to provide remote troubleshooting, step-by-step repair guidance, or direct support for printer repairs. We do offer an in-person evaluation and repair option through our local diagnostic facility: Printer Repair Service (https://bchtechnologies.com/printer-repair-service). Since demand is high, everything runs first-come, first-served, and it may take a few weeks before there's an opening for a drop-off. Our services can be arranged to repair either an entire printer or specific parts, with clear instructions on how the process works. That said, we recognize our rates may not be the most budget-friendly, so we strongly recommend self-help through online research first. You can start on YouTube or by visiting our channel homepage: BCH Technologies on YouTube (https://youtube.com/@bchtechnologies). Use the search icon near the "About" section on the right side of the menu to locate videos by keyword. I receive dozens of messages every day asking if we've made a video for a particular topic, and after nine years of publishing, it's hard to remember every single one-so YouTube search is the quickest way. You may also get helpful recommendations from other channels that cover related repairs.

Thank you again for reaching out and for supporting BCH Technologies and our content. We truly appreciate it, and I hope this explanation helps you understand what H71 means and why it happens on the Procolored L805.