Testing Water heater thermostats


Old 11-08-18, 07:58 AM
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Testing Water heater thermostats

We bought a new house. Since then, the water for showers just doesn't seem to get as hot as we like. I'm to the point where I'm testing out components of our water heater. Both elements pass conductivity test with a reading of 13.x. So I'm testing the thermostats. The instructions I have say that I should be getting zero when I test across the two screws on the upper and lower thermostats (on highest and lowest temp settings). On both, I'm getting 0.4 (multimeeter set at 200 Ohms). I am honestly not sure if that is indicating a problem or not. Thoughts?
Old 11-08-18, 09:12 AM
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The upper thermostat must reach it's set temperature before it will send power down to the lower thermostat. So, when the heater is powered check the output screws of the thermostat. Is 240VAC being sent to the upper element? Then once the upper thermostat reaches temperature and turns off the upper element check the other output (the one that goes to the lower theremostat) and see if it is outputting 240VAC. If not the upper thermostat is bad.

If the upper thermostat is sending power to the lower thermostat check the output side of the lower thermostat. Is it outputting 240VAC. If no then the bottom thermostat is bad. If yes then I'd check the heating element.

Turn off the circuit breaker for the heater. Disconnect the wires to the heating element. Check continuity between the two screws. There should be continuity and resistance. Then check from each screw to the metal base of the element. You should get NO continuity.
Old 11-08-18, 09:53 AM
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Thanks Dane. As I said, continuity passed. As did the short check (no continuity). I'm not sure you answered my question. The instructions I have for testing the thermostats are with the power off. Based on that, they indicated I should get a zero reading on the power screws - I got a .4.
Old 11-08-18, 09:57 AM
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0.4 is essentially zero. You will always get a little resistance in the multi-meter cables, leads, and between the probe tips and screws. What reading do you get when you touch the probe tips to each other? Subtracting that value from 0.4 will give you a more accurate reading.
Old 11-08-18, 07:03 PM
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Have you adjusted the temperature pointers or dials on the thermostats?

Do sink faucets deliver hotter water? Do your showers have anti-scald devices built in that you can adjust? Is there an anti-scald device between the hot and cold pipes above the water heater that you can adjust?

Has the water heater supposedly finished heating for this cycle? Is voltage across each element zero which means no more heating is going on?

When testing resistance or continuity the power must be turned off and at least one of the two places you touch the meter probes to must have everything else unhooked from it.

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