Can I use a multimeter to check for a bad thermostat or heating element in my Rheeem Fury hot water tank
Some checks are surely possible but PLEASE make sure that the 220VAC is absolutely shut down.
In a home we built in 1977, circuit breakers were improperly marked and I, with decades of experience, believed I had turned off the power to our water heater only to find that it was still 'hot' and blew away a screwdriver tip before thinking to check across terminals to see if the voltage was in fact OFF.
You may have the same problem I had twice over ~30 years; that the lower heating element is open/failed.
These typically will gather a coating of mineral deposits and eventually be unable to transfer their heat to water fast enough to avoid overheating and failing.
The limited hot water comes from the fact that the thermostat is checking for temperature at the exit point of the heater; the top.
The thermostat turns on both elements but with only the top one still working it heats 10-15% of the tank capacity and then shuts off.
With your meter set to the lowest Ohms scale (typically 200 Ohms), measure across the element terminals.
You should measure pretty much a short since the elements have an extremely low resistance; on the order of 10-20 ohms, if you measure anything that goes 'off-scale' on the 200 ohm range (normally blinking), the element is shot.
Don't forget to drain the tank before pulling out the element!
If you are in the US, near any city, check your white pages for: Johnstone Supply or check their website to see if one is near you.You will pay 1/3-1/2 hardware store prices for the replacement element - buy two, store the second one.
They are 'wholesale' to the trade but have never been refused.
If you don't feel like wading through their extensive website, you can take the element with you and they can give you what you need.
If you have limited hot water then it is probably one of your heating elements to accurately check an element you will need to drain the heater and cut off the power to it. remove the wires from the element and check resistance across terminals. If it is open then the element is bad .
Most electric hot water heaters have two thermostats, one near the top of the tank and one near the bottom, and are covered by removable metal cover plates. The thermostats are pressed firmly against the bare metal wall of the hot water heaters tank.
The top thermostat usually has a high limit switch that will trip if the water gets too hot. When it trips it shuts off the electricity to both the upper and lower heating elements.
To reset the high limit switch there is usually a red button that you must press. When the upper limit switch trips it is often an indication that something else has gone wrong with the heater.
When the top of the tank is hot the upper thermostat removes power from the upper heating element and transfers the power to the lower thermostat and heating element. If the lower thermostat is defective, then the lower portion of the tank will not be heated and the supply will be greatly reduced.
Check for power at the upper thermostat terminals where the power is sent to the lower thermostat and heating element. If there is no power then the upper thermostat should be replaced. If there is power then check for power at the lower heating element. If there is no power at the lower heating element then replace the lower thermostat.
If there is power to the lower heating element then it should be getting hot. If it is not, replace it. Another possibility is a broken dip tube. Check for a broken dip tube and replace if necessary.
Hope this helps out
Rheem element http://waterheatertimer.org/How-to-troubleshoot-electric-water-heater.html
If wire is bad between upper and lower parts of water heater, and water heater has tight-fitting 2" foam insulation, it usually indicates water heater replacement.
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replaced both thermostats, both elements, flushed tank, inspected annode and dip tube
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