Is the smart valve showing an error code?

Most smart valves have a diagnostic LED that blinks a code after a fault. Check the label on the valve for the code legend. Common patterns: • Steady ON — normal standby or operation • Rapid blink — lockout (count the blinks per cycle) • No light at all — no power to the valve • Slow blink — retrying or waiting Record the exact blink pattern before proceeding — it narrows the diagnosis significantly.

Does the smart valve have power?

Measure voltage at the valve's power input terminals. Depending on the model: • 24 VAC between common (C) and hot (R) — most residential smart valves • Some models require both 24 VAC power AND a separate thermostat call If there is no power at all, trace back through: • Transformer output (should be 24–28 VAC) • Safety limit chain (high-limit, rollout, pressure switch) • Wiring connections and fuse (some boards have a 3A fuse)

What type of lockout code?

Match the LED blink code to the valve's legend. Common smart valve lockout categories: • Ignition failure / no flame detected — most common • Flame without call for heat (false flame) — safety lockout • Internal valve fault — rare but serious • Pressure switch fault — if the valve monitors the pressure switch directly • Limit circuit open — high-limit or rollout tripped Some valves require a full power cycle (disconnect power for 30+ seconds) to reset from lockout.

Is there a call for heat at the valve?

Smart valves typically receive the thermostat call on dedicated terminals (TH/TR, W/C, or similar). Measure 24 VAC across the thermostat input terminals during a call. If the valve has power but no thermostat call: • Thermostat not set correctly • Broken thermostat wire • Open safety in the thermostat circuit (some systems route W through limits before reaching the valve)

Does the valve attempt ignition?

With power and a call for heat confirmed, the smart valve should begin its ignition sequence. Depending on the model this may be: • Spark ignition — you'll hear clicking and see spark at the pilot or burner • Hot-surface igniter — the igniter should glow orange/white before gas is released • Direct spark to main burner — spark directly at main burner tubes If the valve does nothing after receiving a call — no spark, no igniter glow, no gas — the internal control may be failed or a pre-ignition safety check (like pressure switch) may be blocking the sequence.

Does gas flow to the pilot or burner?

The ignition source is active (spark or hot surface). Does gas actually flow? • On pilot-equipped systems: does the pilot gas release and ignite? • On direct-ignition systems: does the main burner gas release? If the igniter is active but no gas flows: • Pilot orifice or tubing blocked • Internal valve not opening the pilot port • Gas supply issue upstream If gas flows and ignites, proceed to flame proving.

Does the valve prove flame?

After the pilot or burner lights, the smart valve must detect flame before proceeding. Measure the flame sense signal: • Flame rectification (flame rod): measure DC microamps — should be 1.5–6 µA • Some smart valves display flame status via the diagnostic LED If flame is visually present but the valve doesn't prove it: • Dirty or failed flame rod • Flame rod not in flame path • Grounding issue (flame rectification requires proper chassis ground) • Cracked flame rod insulator • Wrong polarity on the line voltage supply (some valves are polarity-sensitive)

Does the main gas valve open?

After flame is proved, the smart valve should open the main gas port. On pilot-equipped systems, this is a separate step from pilot gas. On direct-ignition systems, the valve may already be fully open. If flame is proved but the main burner doesn't fire: • Listen for the main valve click • Some smart valves have a timed delay between flame proving and main valve opening • Internal valve mechanism may be stuck • On two-stage valves, first stage may work but second may not

Does the system complete a full heating cycle?

With the main burner running, observe the complete cycle: • Blower engages after fan-on delay • System runs until thermostat is satisfied • Main valve closes when call ends • Blower runs through fan-off delay • Valve returns to standby without error codes If the system drops out mid-cycle, note the LED code and what shuts down first.

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Gas Furnace / Boiler with Integrated Smart Gas Valve (e.g., Honeywell SV9500/SV9600, White-Rodgers 36J, Robertshaw 720-400 series)

Smart Valve / Gas Valve Control Troubleshooting

Step-by-step diagnostic for integrated smart gas valve systems — from call for heat through ignition sequence, flame proving, main burner operation, and shutdown behavior.

Safety Notice

Disconnect power before handling wiring. Gas-fired equipment produces lethal voltages, combustion gases, and hot surfaces. Only trained, qualified technicians should perform these procedures. Follow NFPA 54 and local codes. Never bypass safety controls or force a gas valve open.

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Smart Valve Troubleshooting Overview

Smart valves (integrated gas valve controls) combine the gas valve, ignition control, and flame supervision into a single unit. The control module is built into or mounted on the gas valve body. Common symptoms: • No ignition attempt after call for heat • Spark or hot-surface igniter activates but pilot/burner won't light • Pilot lights but flame isn't proved — valve locks out • Main burner won't open after pilot is proved • System locks out with LED error code • Intermittent operation or mid-cycle shutdown Before starting: • Note any LED status/error codes on the valve • Confirm gas supply is on • Confirm the thermostat is set to call for heat

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Smart Valve / Gas Valve Control Troubleshooting

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