Use a multimeter to check for continuity across the 2-terminal plug

using the genuine Carrier HH84AA018 is recommended to ensure exact timing for pre-purge and post-purge cycles

provided the furnace model specifies the 903905 part number and the airflow meets the minimum requirements to prevent overheating

It features a precise 7-11" WC outlet pressure range (factory set at 8" WC) and includes a factory-installed 12A49 vent limiter

If voltage is present but the load terminals fail to show continuity within the specified timing window—usually 1 to 110 seconds—the internal heater or bimetal disc has failed

Robertshaw 110-285 Thermostat 30067439-890 Use a multimeter to checkRobertshaw 110 285 Left Hand Thread 180F 1 2" 110 285 is the direct replacement for R65RR TS8P