Hydrotherm BM-7989 Gas Valve R-410A What causes a limit switch

What causes a limit switch like this to trip frequently

The kit typically utilizes a White-Rodgers or Honeywell gas valve conversion mechanism

This internal snubber technology effectively eliminates water hammer

while this kit is designated LFRK909-RV

If proper vacuum is present but the SPDT switch does not close

Hydrotherm BM-7989 Gas Valve R-410A What causes a limit switchThe Hydrotherm BM 7989 Gas Valve is an industrial grade 3 4" 2 stage combination gas control engineered for high capacity intermittent pilot appliances. Serving as the direct replacement for VR8304Q4511, this valve manages fuel flow with a 300,000 BTU hr capacity, making it a critical component for Hydrotherm boiler service and commercial furnace maintenance. This unit features a straight through body pattern and is designed for 24 Vac systems,