Diagnose Upper Heating Element — Test the Lower Thermostat
Part of project
How to Test and Replace an Electric Water Heater Thermostat · Step 5 of 9
In this video
To test the upper heating element, first remove the access panel and the insulation behind it. Then, remove the plastic cover over the thermostat. Disconnect the two wires from the element's screw terminals. Set your multimeter to the lowest resistance setting (Ohms, Ω). Touch the probes to the two element screws. A good element will show a reading between 12-20 ohms (the video shows 17.2 ohms). Next, set the multimeter to the highest resistance setting (e.g., 200kΩ) to check for a ground fault. Touch one probe to one of the screws and the other probe to the metal tank body. Repeat for the other screw. A reading of infinity (often shown as '1' or 'O.L.' on a digital meter) indicates the element is not grounded and is good. If you get a resistance reading, the element is faulty.
Goal: Test the upper heating element
- A faulty thermostat can cause the water to overheat and trip the high-limit reset, but a faulty element shorting to ground is the most common reason for a circuit breaker to trip.
Used in this video
- Screwdriver (brand: Husky) — Removing access panel and disconnecting wires.
- Multimeter (brand: Craftsman) — Testing the element for continuity and ground faults.
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FAQs
Why is verifying the power is off with a multimeter so critical, and what happens if I skip this step?
Verifying power is off with a multimeter is the most crucial safety step to prevent electrocution. Skipping this step can lead to serious injury or death. Always use your multimeter to confirm no voltage is present at the thermostat wires before touching any components or proceeding with the repair.
I'm a beginner; what kind of multimeter should I use, and what settings do I need for testing the thermostat?
As a beginner, any basic digital multimeter like the Klein Tools MM420 will suffice. You'll primarily use the 'ohms' (Ω) setting to test for continuity in the thermostats and the 'AC voltage' (V~) setting to accurately verify the power is off at the water heater's terminal block.
How can I tell if my water heater's problem is definitely the thermostat, or could it be something else?
A faulty thermostat is a common cause if you have no hot water, inconsistent temperatures, or lukewarm water. This guide helps you definitively diagnose it with a multimeter by testing for continuity. If both thermostats test good, the issue might be with the heating elements, which would require further testing.
How do I ensure I purchase the correct replacement thermostat for my electric water heater?
Before purchasing, remove your faulty thermostat and note its brand, model number, voltage, and wattage, usually printed directly on the part or the water heater's data plate. Bringing the old part to a plumbing supply store or using online parts finders with your water heater's full model number is the best way to get an exact match.
Diagnose Upper Heating Element — Test the Lower Thermostat
Part of project
How to Test and Replace an Electric Water Heater Thermostat · Step 5 of 9
In this video
To test the upper heating element, first remove the access panel and the insulation behind it. Then, remove the plastic cover over the thermostat. Disconnect the two wires from the element's screw terminals. Set your multimeter to the lowest resistance setting (Ohms, Ω). Touch the probes to the two element screws. A good element will show a reading between 12-20 ohms (the video shows 17.2 ohms). Next, set the multimeter to the highest resistance setting (e.g., 200kΩ) to check for a ground fault. Touch one probe to one of the screws and the other probe to the metal tank body. Repeat for the other screw. A reading of infinity (often shown as '1' or 'O.L.' on a digital meter) indicates the element is not grounded and is good. If you get a resistance reading, the element is faulty.
Goal: Test the upper heating element
- A faulty thermostat can cause the water to overheat and trip the high-limit reset, but a faulty element shorting to ground is the most common reason for a circuit breaker to trip.
Used in this video
- Screwdriver (brand: Husky) — Removing access panel and disconnecting wires.
- Multimeter (brand: Craftsman) — Testing the element for continuity and ground faults.
Frequently Asked Questions
Why is verifying the power is off with a multimeter so critical, and what happens if I skip this step?
Verifying power is off with a multimeter is the most crucial safety step to prevent electrocution. Skipping this step can lead to serious injury or death. Always use your multimeter to confirm no voltage is present at the thermostat wires before touching any components or proceeding with the repair.
I'm a beginner; what kind of multimeter should I use, and what settings do I need for testing the thermostat?
As a beginner, any basic digital multimeter like the Klein Tools MM420 will suffice. You'll primarily use the 'ohms' (Ω) setting to test for continuity in the thermostats and the 'AC voltage' (V~) setting to accurately verify the power is off at the water heater's terminal block.
How can I tell if my water heater's problem is definitely the thermostat, or could it be something else?
A faulty thermostat is a common cause if you have no hot water, inconsistent temperatures, or lukewarm water. This guide helps you definitively diagnose it with a multimeter by testing for continuity. If both thermostats test good, the issue might be with the heating elements, which would require further testing.
How do I ensure I purchase the correct replacement thermostat for my electric water heater?
Before purchasing, remove your faulty thermostat and note its brand, model number, voltage, and wattage, usually printed directly on the part or the water heater's data plate. Bringing the old part to a plumbing supply store or using online parts finders with your water heater's full model number is the best way to get an exact match.