Printer Shows "Temperature Is Too Low - 22°F" After Printhead Cleaning: FFC, Thermistor, and F1 Fuse Troubleshooting

Question:

I am repairing a printer that originally had a clogged black nozzle in the printhead. I manually flushed the printhead with a syringe and cleaning solution, taking care to avoid getting cleaning solution into the electrical connection ports because I understand that this can damage the printhead or mainboard.

After reinstalling the printhead and turning the printer back on, the printer began continuously beeping and displayed the message "Temperature is too low - 22°F."

Because this happened immediately after cleaning the printhead, I am concerned that a small amount of cleaning solution may have reached the electrical connections and possibly blown the F1 fuse on the mainboard.

Does this symptom indicate a blown F1 fuse? Should I send the mainboard to BCH Technologies for diagnosis or fuse replacement, or should I purchase the fuse and replace it myself?

Answer:

Based on the symptoms you described, I would not assume that the F1 fuse is blown simply because the printer displays "Temperature is too low - 22°F." That message points more directly toward the printer receiving an abnormal temperature signal from the printhead temperature-sensing circuit.

Printer printheads commonly incorporate temperature monitoring so that the machine can protect the head when its operating temperature becomes abnormal. Epson documentation for some printer families likewise confirms the use of a printhead temperature sensor or thermistor for monitoring head temperature.

A displayed temperature of 22°F, approximately -5.6°C, is particularly suspicious if the printer is actually sitting in a normal indoor environment. Unless the printer itself is genuinely at approximately that temperature, the reading suggests that the control electronics may not be receiving a normal signal from the temperature-sensing circuit.

Check the Printhead FFC Cables First

The first area I would investigate is the FFC, or flat-flex cable, connection between the printhead and mainboard.

Unplug the printer from AC power before disconnecting or reconnecting any printhead cables. Never insert or remove an FFC cable while the printer is powered.

Carefully inspect each printhead FFC cable for:

• A cable that is not inserted completely into its connector.

• A cable inserted at a slight angle.

• A cable installed into the wrong socket.

• Folded, torn, burned, scratched, or creased conductors.

• Damaged contacts at the end of the cable.

• Ink or cleaning solution on the exposed contacts.

• Residue inside the printhead connector.

• Corrosion or discoloration around the electrical contacts.

• Damage to the locking tabs on the FFC connectors.

A connection can look almost correct while still leaving one or more conductors disconnected. If the conductor carrying the printhead temperature-sensor signal is not making contact, the mainboard can interpret the electrical condition as an extremely low or otherwise implausible temperature.

For that reason, I would thoroughly inspect and reseat the FFC cables before assuming that a fuse or mainboard component has failed.

Cleaning Solution May Be an Important Clue

The timing is significant because the printer worked differently before the manual flushing procedure and produced the temperature warning immediately after the printhead was reinstalled.

That does not prove that liquid entered the electrical portion of the printhead, but it makes moisture contamination one of the important possibilities to investigate.

When manually flushing a printhead, cleaning fluid should remain in the ink/fluid path. If liquid reaches the exposed electronics, connector contacts, FFC cables, or circuitry on the printhead, it can create temporary leakage paths or an electrical short. Depending on where the fluid goes, the result may range from an incorrect sensor reading to permanent printhead or mainboard damage.

If you see or suspect moisture, I would not repeatedly power the printer on to see whether the error disappears. Every additional power-on attempt applies voltage to the affected circuitry.

Disconnect the printer, remove or disconnect the printhead as appropriate, and allow the components to dry thoroughly before further electrical testing. Drying time depends on where the liquid traveled and how much entered the assembly, so there is no reliable universal number of hours that guarantees the electronics are dry.

Avoid using a heat gun or excessive heat to accelerate the process because excessive temperature can damage the printhead, plastics, adhesives, FFC cables, and connectors.

Does the 22°F Reading Mean the F1 Fuse Is Blown?

Not necessarily.

The F1 fuse should be tested rather than diagnosed from the temperature message alone.

A mainboard fuse generally protects a particular electrical supply circuit. If the fuse supplying the printhead drive circuitry opens, the printer can develop serious printhead-related faults, but an implausible temperature reading by itself is not enough evidence to conclude that F1 has failed.

In this situation there are several possibilities, including:

1. The printhead FFC is not seated correctly.

2. One or more FFC conductors or contacts are damaged.

3. Cleaning solution is contaminating a connector or electrical circuit.

4. The printhead's temperature-sensing circuit has been damaged.

5. There is an open circuit between the temperature sensor and mainboard.

6. There is a short or leakage path caused by remaining fluid or corrosion.

7. The mainboard's temperature-sensing/input circuitry has been damaged.

8. A fuse or another board-level component has failed.

The symptom alone cannot distinguish among these possibilities.

Test the F1 Fuse Before Replacing It

If you are comfortable using a multimeter and working on electronics, testing the F1 fuse for continuity is much better than replacing it based on suspicion.

With the printer unplugged and unpowered, locate the correct fuse and test across it with a multimeter in continuity or resistance mode.

A good fuse should show continuity and very low resistance. An open fuse will show no continuity or an open-circuit reading.

However, identifying the fuse correctly matters. Labels such as F1 are board-designator names, and their function can vary between different printer models and mainboards. Without the exact model and board documentation, I would not assume that every fuse marked F1 performs exactly the same function.

Do Not Bridge the Fuse

If you discover that the F1 fuse is open, do not bypass it with a wire, solder bridge, or oversized fuse.

A fuse usually opens because excessive current flowed through the protected circuit. If cleaning solution has created a short inside the printhead, or if the printhead electronics have already failed short-circuit, replacing the fuse without correcting the underlying problem can cause the new fuse to open immediately.

Bypassing it can be considerably worse because the fuse can no longer protect the circuit. The excessive current may then damage traces, MOSFETs, drivers, power circuitry, the printhead, or other mainboard components.

The important question is therefore not only:

"Is F1 blown?"

It is also:

"If F1 is blown, what caused it to blow?"

A Useful Diagnostic Order

For this particular situation, I would approach the repair in this order:

First, stop repeatedly powering the printer on. Disconnect AC power while inspecting the printhead circuit.

Second, inspect the printhead and FFC cables carefully. Look for moisture, contamination, burned contacts, bent cable ends, incorrect alignment, or damaged connectors.

Third, allow any possibly contaminated electrical areas to dry thoroughly. Do this before applying power again.

Fourth, reseat the printhead FFC cables. Verify their orientation and alignment before locking the connectors.

Fifth, check the F1 fuse with a multimeter. Do not replace it unless testing confirms that it is actually open.

Sixth, if the fuse is good but the printer continues reporting approximately 22°F, investigate the printhead temperature-sensing circuit rather than concentrating exclusively on the fuse. At that point the problem could be the FFC path, connector, printhead thermistor/sensing circuitry, or the corresponding mainboard input circuit.

If you have access to another known-good compatible printhead or board, controlled substitution can sometimes help isolate which side contains the fault, but I would be cautious about connecting a questionable printhead to a known-good mainboard. A printhead with an electrical short can potentially damage the replacement board as well.

Could the Printhead Already Be Damaged?

It is possible, but I would not conclude that yet.

Because this occurred immediately after the printhead was removed, flushed, and reinstalled, a connection problem remains a very reasonable first possibility. A slightly crooked FFC cable or contaminated contact can create symptoms that resemble a much more serious electronic failure.

On the other hand, if cleaning solution reached the electrical circuitry while the head still contained moisture and the printer was powered, permanent damage to the printhead electronics or mainboard is also possible.

Therefore, I would work from the least destructive and easiest things to verify toward the more expensive conclusions:

FFC connection → moisture/contamination → fuse continuity → printhead electrical fault → mainboard circuitry.

Regarding Mainboard Repair

At this time, we do not work on this particular mainboard, so sending this specific board to us for an F1 replacement would not be the path I would recommend.

Before purchasing or replacing any fuse, I would first verify the existing fuse with a multimeter. If the F1 fuse still has continuity, replacing it will not address the 22°F temperature indication.

If F1 is actually open, investigate the possibility of a short in the printhead and FFC circuit before installing another fuse. Otherwise, the replacement may fail as soon as power is applied.

Also, be sure that any replacement fuse matches the original specifications. Choosing a fuse merely because it physically fits the board is not sufficient.

Overall, based on what you have described, there is still a reasonable possibility that neither the mainboard nor the printhead has suffered permanent damage. I would begin with complete drying, careful FFC inspection and reseating, followed by a continuity check of the fuse. The unusual 22°F reading makes the printhead temperature-sensing path particularly important to investigate.

Addressing printer problems can be complicated because so much of the diagnosis depends on hands-on inspection and testing. For that reason, we're unable to provide ongoing remote troubleshooting, individualized repair guidance, or remote technical support for printer repairs. We do offer in-person evaluation and repair through our printer repair and diagnostic service https://bchtechnologies.com/printer-repair-service. Because demand is high, the service operates on a first-come, first-served basis, and there may be a wait of several weeks before a printer can be scheduled for drop-off. Our repair options cover either complete printers or, where applicable, specific components, with instructions explaining how to proceed. We also recognize that professional repair is not always the most economical option, so we strongly encourage self-help and independent research when appropriate. A good starting point is YouTube and the BCH Technologies YouTube channel https://youtube.com/@bchtechnologies. On our channel homepage, use the search icon near the About section to search for your printer model, error, printhead, FFC cable, fuse, or other specific topic. We receive many requests asking whether we have a particular video, and after producing repair videos for more than nine years, it is difficult to remember every video individually. Using YouTube's search function is usually the fastest approach, and it may also bring up useful repair information from other creators.

Thank you again for reaching out to BCH Technologies and for taking the time to describe the problem in detail. We appreciate your continued support of our work and hope this information gives you a safer and more systematic direction for diagnosing the temperature warning before replacing the fuse or mainboard.