Honeywell SmartValve Flash Codes: SV9510 and SV9520

By Ray Bennett · Updated 2 October 2026 · 4 min read · Checked against the maker’s manual

Honeywell SmartValve Flash Codes: SV9510 and SV9520

Short answer

On a Honeywell SmartValve SV9510 or SV9520, a bright and dim heartbeat is normal. 2 and 3 flashes are the airflow proving switch, 4 is an open limit or rollout switch, 5 is flame when there should be none, and 6 is a lockout that retries after an hour. A 6 followed by more flashes tells you why it locked out, and 10 is reversed polarity.

The Honeywell SmartValve is a gas valve and ignition control in one box, used in furnaces, boilers, water heaters and other gas appliances. The SV9510 and SV9520 light a hot surface igniter, and a small light on the valve tells you what they are doing.

Everything on this page comes from Resideo’s installation instructions 69-2014-01 for the SV9510/SV9520 SmartValve System Controls. Resideo says the troubleshooting behind each code is for a trained, experienced service technician, so this page covers reading the light and the checks around it.

Before you start

What to carry: a torch and a pen. Ten minutes.

Gas or electric? Gas, natural gas or propane. The SmartValve runs on 24 volts and fires a 120 volt igniter.

Check the model. SV9510 or SV9520 is printed on the valve. Other SmartValve models work differently.

Read it before you cycle anything. Resideo’s steps read the light with the call for heat still on, without switching the thermostat off and on and without cutting the power by opening an interlocked door.

Where you stop. If you smell gas. Resideo’s homeowner instructions start with turning off the gas at the appliance service valve, and on propane, at the tank too.

5 flashes: flame when there should be none. Resideo says the flame signal is out of sequence, with flame at the main burner. Turn the gas off and call a technician.

4 flashes and the rollout switch. An open rollout switch means flame came out of the burner area. Find out why before anyone resets it: what a rollout switch is telling you.

What the light means

Resideo's SmartValve light: a heartbeat is normal, 2 to 6 flashes are faults, and 5 is the one to stop at.

Check 1Free, two minutes

Read the light

Heartbeat, bright then dim. Normal operation. Resideo says it shows whenever the system is powered, when the valve is paired with the ST9160 fan timer.

Off. No power to the control: the line voltage, the 24 volt supply, the fuse on the ST9160 fan timer if it has one, or the wiring harness.

2 flashes. The airflow proving switch stayed closed more than 30 seconds after the call for heat, so the inducer is not started. Resideo names a switch stuck closed, or one miswired or jumpered.

3 flashes. The airflow proving switch stayed open more than 30 seconds after the inducer started. The control waits five minutes and tries again.

4 flashes. The limit string is open: a rollout switch or the high temperature limit.

6 flashes. System lockout. Resideo says that after a one hour delay the control resets and tries again if the call for heat is still there.

10 flashes. On models that sense polarity, the line voltage is reversed. That is wiring for an electrician.

The 6 plus codes

On polarity sensing models, 6 flashes, a pause, then a second count gives the reason for the lockout.

Code	What Resideo says
6+1	Four failed trials for ignition in this call for heat
6+2	More than five recycles, the last one flame lost while running
6+3	More than five recycles, the last one the airflow proving circuit opening while running
6+4	More than five recycles, the last one the limit circuit opening while running
6+5	The flame went away after code 5
6+6	Not used
6+7	The valve’s own hardware check failed

Check 2

Work the owner checks

3 flashes or 6+3: the air path. Resideo lists the airflow proving switch, its tubing and wiring, and anything blocking the air intake or the exhaust flue: the places a pressure switch fault hides.

4 flashes or 6+4: the limits. Resideo adds the circulating fan and anything in the furnace or ducts blocking the air through the heat exchanger. Start with the filter: why a furnace overheats and cuts out.

6 or 6+1: the gas and the flame. Resideo’s list starts with the gas supply off or too low, then the igniter, the grounding and a contaminated flame rod: how to clean a flame sensor safely.

The ignition switch. For a 3 flash code, Resideo’s first check is that the appliance’s ignition system control switch is on.

Clearing it and starting again

Check 3Free, five minutes

Restart it the way Resideo does

After the repair. Resideo says to set the thermostat below room temperature for 10 seconds, then above it, to start a new call for heat, and to watch the ignition sequence.

A 6 plus lockout. Resideo says the valve tries again after one hour if the call for heat is still there, and resetting the thermostat starts a new try at once.

6+5 and 6+7. Cycle the call for heat. Resideo says to replace the SmartValve if code 5 repeats with no flame visible, or if 6+7 repeats.

Questions people ask

What does 3 flashes mean on a Honeywell SmartValve?

The airflow proving switch stayed open more than 30 seconds after the inducer started. The control waits five minutes and tries again. Check the vent, the switch tubing and the ignition switch.

What does 6+1 mean?

Four failed tries to light in this call for heat. Resideo starts with the gas supply, then the igniter, the grounding and the flame rod.

What is the heartbeat light?

Normal operation: a bright and dim pulse whenever the SmartValve is powered, when it is paired with the ST9160 fan timer.

How do I reset a SmartValve lockout?

It tries again by itself after an hour. Resetting the thermostat starts a new try straight away. Read and note the code first.

What does 5 flashes mean?

Flame sensed out of sequence, with flame at the main burner. Turn the gas off and call a technician.

What does 10 flashes mean?

The line voltage polarity is reversed at the SmartValve. The power wiring needs correcting by an electrician.

Sources: Resideo (Honeywell) installation instructions 69-2014-01 for the SV9510/SV9520 SmartValve System Controls