RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
Residential Electric – continued
A-7 Voltage Check Voltage Checks
These tests are conducted on the heater, below the junction box.
Complaint: No Hot Water
Test Conditions:
Tank is full of cold water (or at least 15°F below the upper thermostat setting).
Power on
Upper thermostat calling for heat
Multimeter set to the proper AC voltage scale
Test between upper high limit terminals 1 and 3
If … … then
the proper voltage is not present
(disconnect)
check power from the breaker (fused
disconnect).
the proper voltage is present check wiring in heater junction box
continue to next step.
Test between upper high limit terminals 2 and 4
If … … then
the proper voltage is not present push the reset button – if this establishes
proper voltage, conduct thermostat and
element checks before changing the high
limit.
pushing the reset does not restore voltage replace the high limit.
the proper voltage is present continue to the next step.
Test between upper high limit 4 and upper thermostat 2
If … … then
the proper voltage is not present high limit
and upper thermostats 2
• check the jumper between upper
thermostat 1 and high limit 2.
• replace the upper thermostat
the proper voltage is present • conduct upper element checks.
• top 1/3 of tank should be hot.
A.O. Smith Water Products Company Technical Training Department
©2005 Ashland City, TN
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