The HI‑98804 is a handheld, microprocessor‑based recording thermometer that accepts K, J, or T type thermocouples and prints data via an integrated thermal printer. Common failures include loss of display or printing output (often due to depleted battery or damaged LCD), drift in temperature accuracy (typically from thermocouple connector corrosion or internal sensor degradation), and erratic error codes caused by firmware glitches or loose input contacts. First‑check diagnostics: verify the 9 V battery voltage and replace if below 6 V; inspect all thermocouple leads for continuity and secure mounting; and confirm that the printer cartridge is correctly seated, printing a test page to rule out mechanical blockage.[oss-gpt-20b]