Procolored L1800 Paper and Ink Lights Flashing with Fatal Error Code 71H After Replacing Mainboard, Printhead, and Carriage

Question:
I have a Procolored L1800. I already replaced the motherboard, printhead, and carriage, but the printer is still showing both the paper and ink lights flashing. I also tried resetting the waste ink counter, but it keeps reporting a fatal error with code 71H. What should I check next?

Answer:

Based on what you described, the fact that the paper light and ink light are both flashing means the printer is not dealing with a simple consumable issue. On the Epson L1800 platform and many of its modified DTF variants such as Procolored units, dual flashing lights often point to a fatal mechanical or sensor-related error, not just a waste ink counter problem.

The most important clue in your case is the fatal error code 71H. That code usually indicates that the printer has detected a serious fault during initialization, and in many cases it is related to the carriage path, sensor reading, or carriage/APG-related detection failure. Even though you already replaced the motherboard, printhead, and carriage, the fault may still remain because the problem is often caused by something peripheral to those major parts, such as:

• a disconnected or damaged sensor cable

• an APG or carriage-related sensor not reading correctly

• a timing issue during carriage startup

• a short or improper connection on the printhead or carriage board

• a mechanical obstruction that prevents proper carriage movement

• a mismatch or defect in one of the replacement parts

Also, the fact that the printer throws a fatal error during waste ink reset is important. A waste ink reset only clears the maintenance counter. It does not override a true hardware fault. So if the printer has an active fatal error like 71H, the reset utility will usually fail or refuse to complete the process because the printer cannot pass its internal startup checks.

The next best step is to confirm the printer's stored error data using Epson's Adjustment Program. This is one of the most direct ways to identify what the machine is actually seeing. Here is the process:

Open the Adjustment Program and select the correct USB port showing your printer's name.
Choose Particular Adjustment Mode.
Scroll to Printer Information Check.
Click Check.
The latest recorded error will usually appear as Error Number 1, which is the most recent and often the most useful for diagnosis.

That error history can help confirm whether 71H is the primary failure or whether another underlying error occurred before it. Sometimes the visible panel symptoms are only the final result, while the actual root cause is recorded in the error log.

For interpreting the code, search "BCH Epson Error" online to find our resource on Epson's hidden or less-documented error code meanings. These error references can sometimes point to issues like APG sensor faults, carriage initialization problems, or other sensor-related failures that are not obvious from the blinking lights alone.

Since you already replaced several major parts, I would especially inspect the following areas carefully:

1. Carriage movement
   Make sure the carriage moves freely by hand when the printer is powered off. If there is resistance, binding, or scraping, the printer may fail its startup routine and trigger a fatal error.

2. Encoder strip
   Check whether the encoder strip is clean, seated correctly, and passing properly through the encoder sensor. If the strip is dirty, twisted, misaligned, or not read correctly, the printer can misjudge carriage position and throw a fatal error.

3. Carriage cables and FFC cables
   Even a slightly crooked, damaged, or partially inserted flat cable can cause fatal startup errors. Inspect for bent pins, torn cable ends, reversed insertion, or carbonized contacts.

4. Printhead connection and possible short
   A new printhead does not always guarantee a good circuit. If there is any short on the head, head board, or cable path, the printer may stop immediately with a fatal code.

5. APG or paper gap related detection
   On some Epson-based units, if the printer cannot correctly read the APG position or detect carriage height status, it may register a fatal error. This can happen even after replacing the carriage assembly if the sensor or its cable is still bad.

6. Mainboard compatibility
   If the replacement motherboard is from another revision or is not perfectly matched to the printer's configuration, that can also create abnormal startup behavior. This is especially relevant on converted or third-party modified L1800 platforms.

7. Waste ink reset expectations
   Since your reset attempt keeps ending with a fatal error, I would not focus on the waste counter at this stage. The counter reset is probably not the root issue. The hardware fault needs to be resolved first.

For a quick walkthrough on checking printer error information, you can watch this short video on our channel: BCH Technologies video walkthrough [https://youtube.com/shorts/FPZzpyYuZLE].

You also shared this video link, which may be connected to the discussion around your issue: YouTube comment thread [https://www.youtube.com/watch?v=u0vJcxWKKGE&lc=Ugw4oEvG_yhawpOVYWd4AaABAg].

Printer issues like this can be difficult because they are very hands-on by nature. Because of that, we are not able to provide remote troubleshooting, repair suggestions, or step-by-step repair support beyond general guidance. We do offer an in-person evaluation and repair option through our local diagnostic facility, BCH Technologies Printer Repair Service [https://bchtechnologies.com/printer-repair-service]. Due to demand, repairs are handled on a first-come, first-served basis, and it may take a few weeks before we are able to work on a dropped-off printer. Our service can be arranged either for a complete printer or for specific parts, with instructions provided for each option. That said, we recognize that our repair rates may not be the cheapest route. For that reason, we strongly encourage self-help research whenever possible. A good place to start is YouTube or our channel homepage at BCH Technologies YouTube Channel [https://youtube.com/@bchtechnologies]. You can use the search icon next to "About" on the right side of the menu bar to look for videos on your exact topic. I get many messages every day asking whether we have a video for a certain issue, and after producing videos for so many years, it is hard to remember every one offhand. Using YouTube search is usually the fastest method, and it may also surface useful videos from other creators.

Thank you again for reaching out to us and for supporting BCH Technologies. We truly appreciate your patience, your engagement, and your support of our work.