The part(s) or condition(s) listed below for the symptom Water heater not heating are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
Gas Water Heater Not Heating? Gas Water Heater Troubleshooting
Gas Water Heater Leaking? Gas Water Heater Troubleshooting
Electric Water Heater Too Hot? Electric Water Heater Troubleshooting
Electric Water Heater Not Heating? Electric Water Heater Troubleshooting
Electric Water Heater Leaking? Electric Water Heater Troubleshooting
Gas Water Heater Pilot Not Lighting? Gas Water Heater TroubleshootingSome gas water heaters have a thermocouple. The thermocouple detects the pilot flame. If the thermocouple does not detect a flame, it will prevent the gas valve from opening.
On gas water heaters with a power vent the blower assembly is plugged into a 120 volt wall outlet. To confirm there is power at the wall outlet you can plug another working appliance into the outlet or test for voltage with a multimeter. Most electric water heaters require 240 volts to operate. Confirm the breaker is on or the fuses have not blown. You can test for power at the top two terminals on the upper limit thermostat or at the incoming power wires under the access panel.
Most limit switches are resettable. If the limit switch or thermostat has a reset button on the back you should be able to reset it. If the button is popped out the limit switch or thermostat has tripped. You can try resetting it by pressing the button. You should hear a click when it resets. You can check the limit switch or thermostat for electrical continuity with a mutimeter.
The pilot ignites the water heater’s gas burner. If the pilot does not light, the water heater will not heat. Sometimes, carbon deposits can build up on the pilot and eventually create a restriction. If the pilot is restricted, try removing it and clearing it with a stiff brush and/or compressed air. If the pilot cannot be cleaned, replace it.
The gas valve opens to allow gas to enter the burner. If the gas valve does not open, the burner will not light, and the water heater will not heat. First, ensure that the ignition source is working properly. Second, ensure that the gas valve has pressure. If the ignition source is working, and the gas valve has pressure, consider replacing the gas valve and thermostat.
As a precaution, most electric water heaters have a safety limit switch attached to the top of the upper thermostat. A reset button on the limit switch will pop out and disconnect the power to the elements if the water gets too hot. The button can be pressed in to reset it. The heating element and thermostat will need to be checked and replaced, if needed, to prevent the water from overheating and causing the reset button to trip again.
The draft inducer fan motor draws air into the burner and then exhausts it out the flue. As the air flows through the draft inducer assembly, it closes a vacuum switch to signal that proper air flow is present. If the inducer motor is not working properly, the water heater will not heat. Over time, the bearings on the inducer motor wear out. The inducer motor could also have a plugged vacuum port. If the vacuum port is plugged, the motor will not be able to close the vacuum switch, causing the ignition process to stall.
The ignition module cycles the igniter or sparker on to light the burner. If the ignition module is defective, the burner will not light. To determine if the ignition module is defective, check to ensure that power is getting to the ignition module. If power is getting to the ignition module, but the burner will not light, consider replacing the ignition module.
The gas valve opens to allow gas to enter the burner. If the gas valve does not open, the burner will not light, and the water heater will not heat. First, ensure that the ignition source is working properly. Second, ensure that the gas valve has pressure. If the ignition source is working, and the gas valve has pressure, consider replacing the gas valve assembly.
To determine if the heating element is defective, use a multimeter test it for continuity. If the heating element does not have continuity, replace it.
When the main burner lights the gas valve senses the flame through the flame sensor. If the main burner will not stay lit the flame sensor may be dirty or damaged and will need to be replaced. Most flame sensors are part of the igniter assembly and are not sold separately.
Most limit switches are resettable. If the limit switch or high limit thermostat has a reset button on the back you should be able to reset it. If the button is popped out the limit switch or thermostat has tripped. You can try resetting it by pressing the button. You should hear a click when it resets. You can check the limit switch or high limit thermostat for electrical continuity with a mutimeter.
The pressure switch closes when the proper airflow is achieved, signaling the control board to continue the ignition process. If the pressure switch is defective, the ignition process will stall, and the water heater will not heat.
The temperature control thermostat senses the temperature in the water heater and regulates it accordingly. If the thermostat is defective, replace it.
The thermostat senses the temperature in the water heater and regulates it accordingly. If the thermostat is defective, replace it.
The igniter lights the pilot. When the pilot is sufficiently lit, the gas valve will allow gas to enter the main burner, and the ignition process will continue. If the igniter is defective, the pilot will not light, and the ignition process will stall.
Flammable vapors should always be kept away from the water heater. If your water heater has a flammable vapor system (FVIR), sometimes identified as a temperature sensor, the sensor may have tripped which will cause the water heater not to heat the water. It is recommended to replace a tripped sensor rather than reset it. See owner's manual for more information.
Most limit switches are resettable. If the limit switch or thermostat has a reset button on the back you should be able to reset it. If the button is popped out the limit switch or thermostat has tripped. You can try resetting it by pressing the button. You should hear a click when it resets. You can check the limit switch or thermostat for electrical continuity with a mutimeter.
