The Honeywell RM7890A1015 is a microprocessor‑based on‑off primary burner control module that operates from 120 V AC and includes a shutter drive for gas or oil single‑burner applications. Common failures include loss of power to the relay board, burnt fuse contacts in the internal 120 V supply, failed microcontroller ICs (often due to overheating), and faulty latch relays that cause intermittent burner cycling. Begin diagnostics by verifying line voltage at the module’s input terminals, inspecting the internal fuse and relay contacts for burn marks or corrosion, and checking the status LEDs/diagnostic outputs on the control board; if power is present but the unit does not cycle, test the microcontroller’s supply rails and reset pin logic before replacing the IC.[oss-gpt-20b]