A.O. Smith THR-160 Installation Instructions And Use & Care Manual page 62

Residential gas tankless water heater
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TROUBLESHOOTING
Error
Error Type
Code
E417
Flame Sensor Fault
E418
Exhaust High Temperature
E420
Gas Valve - SV2
E421
Pressure Switch
E422
Venturi Assembly
E426
Condensate Drain Overfl ow
E427
Flow Control Valve
62 • Residen al Gas Water Heater Use and Care Guide
1. Check the fl ame sensor wire for a short or disconnec on. Correct any loose con-
nec ons and replace any damaged wire/connector.
2. Check the inlet & heat exchanger thermistor sensor wires for a short or discon-
nec on. Correct any loose connec ons and replace any damaged wire/connec-
tor.
3. Remove the inlet & heat exchanger thermistors (do not lose the o-ring) and
check for any dirt or debris. Clean with an Emery cloth. If the either thermistor is
damaged, replace it.
1. With the water heater power disconnected, check the exhaust vent and air
intake piping for any blockages. Remove any blockages.
2. Remove the exhaust thermistor (do not lose the o-ring) and check for any dirt or
debris clean with Emery cloth. If the thermistor is damaged, replace it.
3. If the error s ll occurs, contact a qualifi ed service technician.
1. PCB detects an incorrect voltage from the gas valve's SV2. Correct any loose
connec ons and replace any damaged wire/connector. If the error s ll occurs
contact a qualifi ed service technician to replace the gas valve.
1. Check the pressure switch wires for a short or disconnec on. Correct any loose
connec ons and replace any damaged wire/connector.
2. Check the pressure tube for loose connec ons, debris, or blockages. Correct any
issue immediately.
3. With the water heater power disconnected, check the exhaust vent and air
intake piping for any blockages. Remove any blockages.
4. If the error s ll occurs, contact a qualifi ed service technician.
1. Check the venturi assembly wires for a short or disconnec on. Correct any loose
connec ons and replace any damaged wire/connector.
2. If the error s ll occurs, contact a qualifi ed service technician.
1. Place a bucket under the water heater to catch any water.
2. With the water heater off , check the condensate drain for any blockages. Remove
any blockages.
3. With the water heater off , check the condensate trap for any blockages. Remove
any blockages.
4. Check the condensate drain wires for a short or disconnec on. Correct any loose
connec ons and replace any damaged wire/connector.
5. Verify the condensate drain line is installed correctly, reference "Condensate
Drain" on page 39. "
1. Check the fl ow control valve wires for a short or disconnec on. Correct any loose
connec ons and replace any damaged wire/connector.
2. Remove the fl ow control valve and inspect for any debris or damage. Replace if
needed. First follow the draining procedure in the Unit Draining & Power Outage
sec on in this manual.
Procedure

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This manual is also suitable for:

Thr-180Thr-199

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