Tank-style electric water heaters use two heating elements to warm the water, one at the bottom and one nearer the top. Power surges, mineral build-up and age can cause either element to fail or burn out. If your water heater produces only lukewarm water, suspect a bad top element. If it produces hot water in short supply, the probable cause is a bad bottom element. Test both to be certain. Follow these steps to check the heating elements in a hot water heater.
Switch off the power to the water heater at the main electrical panel.
Locate the electrical access panels, one near the base of the tank and one nearer the top. Beginning with the top element, remove the panel's screws with a screwdriver. Take off the panel and remove insulation behind it to uncover the heating element.
Disconnect either of the two electrical wires screwed into the element terminals. It is not necessary to disconnect both wires to test the element.
Set the multimeter or Ohmeter to read Ohms, and set the scale to RX1. Touch one probe to each of the two terminal screws. If the needle moves at all, or if there is any reading besides "infinity" on a digital readout, the element is good. If it doesn't move, or displays "infinity," no electricity is flowing through the element and it should be replaced.
Complete replacement or repairs as necessary. Reconnect the wire to the element terminal. Replace the insulation and reinstall the access panel.
Repeat the process on the bottom element. Restore power to the water heater from the main electrical panel.