AO Smith Water Heater Error Code 7 (7 Flashes): Gas Control Failure (Meaning, Causes, Fixes)

What the code means

A. O. Smith gas water heaters report problems by blinking the LED status light on the gas control a set number of times, pausing about 3 seconds and repeating. What 7 flashes means depends on which kind of heater you have. On the standard atmospheric-vent, standing-pilot models covered by A. O. Smith's Residential FVIR Gas Water Heater Service Handbook (Series 300/301 GCV, GCVH, GVR, GCVL, GVRL, GCVT and XCV, XVR, XCVL, XGV, XVRL, XCVT), the Honeywell thermopile-powered gas control/thermostat lists 7 Flashes as "Internal control failure", and the only repair given is to turn the control knob OFF, turn the main gas supply OFF and replace the gas control valve/thermostat. On power direct vent and power vent models with hot surface ignition and an electronic Honeywell gas control (for example the 300 Series installation manual and the GPVL service handbook), the status-code table lists Seven Flash, three second pause as a Flammable Vapour Sensor Lockout, and the matching corrective action in the 300 Series manual is: if this happens, replace the gas control. Check which table applies by looking at your heater: a knob with a Pilot setting and a piezo igniter button is the standing-pilot type; a heater plugged into 120 V with a blower on top is a power vent type. Don't confuse 7 flashes with 4 flashes on the standing-pilot control, which A. O. Smith uses for an over-temperature (ECO) condition, or with 8 flashes, which on that control means the pilot flame is still present with the knob set to OFF.

Likely causes

• Standing-pilot models: a failure inside the gas control valve/thermostat itself. A. O. Smith's handbook lists 7 flashes as internal control failure with replacement of the gas control as the fix
• Power direct vent / power vent models: the gas control has locked out on its flammable vapour sensor (Seven Flash in the status table), for which the 300 Series manual's corrective action is to replace the gas control
• Flammable vapours near the heater (gasoline, paint thinner, solvents or similar) are what FVIR (flammable vapor ignition resistant) heaters are designed to guard against, so treat any such smell as a safety issue before anything else
• Misreading the code: counting 4 or 8 flashes as 7, or reading the wrong table for your heater type, which changes the meaning

Safe DIY checks

1. Count the flashes carefully over a few cycles. Each code is a series of flashes followed by a 3-second pause, then it repeats. Make sure it's really 7 and note whether your heater is a standing-pilot (knob with Pilot setting) or power vent (plugged in, blower on top) model.
2. If you smell gas, don't touch any switches or try to relight anything. Leave the house and call your gas utility from outside.
3. Look around the heater for gasoline cans, paint, solvents, cleaners or anything else that gives off flammable vapours, and move them well away. Air out the area.
4. Standing-pilot models: turn the gas control knob to OFF and turn off the gas supply valve to the heater, as A. O. Smith's handbook says. The handbook's next step is to replace the gas control valve/thermostat; there is no reset for this code.
5. Power direct vent / power vent models: A. O. Smith's corrective action for this status is to replace the gas control. Turn the heater off and unplug it until it's been looked at.
6. Write down the model and serial number from the rating plate and check whether the heater is still under warranty before buying a new gas control. A. O. Smith lists a Technical Assistance hotline on its warranty sheet.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• 110 Bradford White Gas Water Heater 110
• 123 Bradford White Gas Water Heater 123
• 002 AO Smith Electric Water Heater 002
• 031 AO Smith Electric Water Heater 031
• 084 AO Smith Heat Pump Water Heater 084

All AO Smith codes →

Sources

1. A. O. Smith Residential FVIR Gas Water Heater Service Handbook, Series 300/301 standing-pilot models (copy hosted by InspectApedia): Diagnostic Flash Codes, 7 Flashes = internal control failure, replace gas control valve/thermostat; 4 and 8 flash meanings
2. A. O. Smith 300 Series power direct vent gas water heater Installation and Operating Manual (ManualsLib, pp. 56-58): System Status and Error Codes (Seven Flash = Flammable Vapour Sensor Lockout) and Corrective Actions
3. A. O. Smith GPVL-50 power vent Service Handbook (ManualsLib, p. 38): Gas Control LED Status Codes table