How to Test if Your Fireplace Main Control Valve is Bad

Time to Complete:  5  minutes

Recommended Tools

One way to test if your main control valve is bad is by testing resistance.  We can do this with our Digital Multimeter.

First lets make sure it is in the correct setting.  We what it in the Ohm’s setting (Ohms is basically a term that refers to resistance).  This is sometimes shown in symbol form:  Ω

First, find you need to find “Zero” but touching your multimeter leads together.  If it reads anything other than zero, you’ll want to subtract this number from the number you will read on the valve.  To test the valve, disconnect all wires from the TP and TH terminals, then place your meter leads on these terminals.  You should get a reading that should fall within the following parameters:

    • SIT 820 ‐1.75 to 2.75 R
    • Honeywell VS8420 ‐3.1 to 3.6 R
  • Robert Shaw/Dexen – 1.5 to 1.7 R

A SIT 820 valve looks like this:



A Honeywell VS8420 valve looks like this:


Honeywell Valve


A Robert Shaw/Dexen Valve looks like this:

Robert Shaw

Gas Valves


SIT 820 Valves

Robert Shaw/Dexen Valves

Safety Pilot/ Manual Valves