I have read lots of do it yourself water heater tutorials and a lot of them from the top search pages say the same thing. But I have yet to see a easy to understand tutorial on checking the water heater elements, and why the water heater isn't working. While these do it yourself tutorials explain some what how to check the element most of them tell nothing about checking the thermostat and they leave out valuable information.
So I am going to explain how “I" go about troubleshooting the water heater elements and the thermostat. First thing you need to do is check to see if you have power going into the water heater, you can do this with a volt meter, some volt meters only require you to hold the meter up to the wires, if the meter gives off a constant buzz its got power, if it beeps only once then you don't. If you do great. If you don't then there is a problem at the breaker, it could have got tripped, resetting the breaker will usually solve this problem.
Now lets get to testing the water heater elements and the thermostat, you will need a volt meter that has a OHMS or resistance setting on it. Before you start taking the panels off and playing with the wires secure the power. I repeat Secure the power to the water heater!. Next step is to take off the two access panels so you can access the thermostat and the heater element. Before you start testing the elements look at the thermostat to see if the reset button is tripped. If it is the little red button will be popped out just simply push it back in and your problem should be solved, if it is not let us get on to testing the elements.
Now hold your meter up to the wires to again confirm THAT THE POWER IS OFF!! With a screw driver loosen the screw or bolt to one of the wires on the element, it doesn't matter which wire you loosen it just has to not be touching the anything on the element. Now set your volt meter to OHMS, when the volt meter is set to OHMS it should read 1. Put one screw and keep it there, the probe on the other screw, if the meter reads 1. (open) then its good, if it reads something like .003, .006 or “0" (closed) which it eventually will read 0 it is a bad element and must be replaced. Then you will do the same thing to the other element.
The process is the same with the water heater thermostat but it has more connections and wires then the element does. Remove a wire from the thermostat, again, it does not matter which one. Keep one probe from the meter on the first screw, then use the second probe to test each screw on the thermostat verifying they all are reading 1 on the OHMS. Thats it, very very simple. If you do in fact discover that you have a bad element or thermostat then you will have to replace. For information on that you can visit my blog thats listed below.
I hope this article cleared things up on whether you need a new water heater or not. And with that note the ONLY time you would need to replace a electric water heater is if its so old that its leaking from the exterior of it, like the bottom part. If its leaking from the top you could change the supply lines or nipples in most cases, but really folks, the elements and the thermostat make the water heater work.
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