water too hot, Thermostat(s)both turned down

[58chevy]

I am thinking this is not good if the water is just as hot with the stats both turned all the way down? Thermostats bad or other?

[RegUS_PatOff]

sounds like the Thermostat..

Gas, Electric, Oil ?

model number ?

[58chevy]

Electric model # C05 4020RT973 0 State Industries 40 gal elements / both are 4500 watts.....limit still trips as well...I did have a period of time about a year ago that I consistantly had to reset for three four weeks once or twice a week. both thermostats are fully turned down to stops, Unit has been regularly drained since new approx 8-9 years ago. Thanks for the response.

How do I know which thermostat to replace or just do both? Installer told me to keep the upper turned higher or lower than the bottom but really don't remember at this point Did not leave manual / owners guide with me.

[RegUS_PatOff]

I can't find any info on that model number (yet).

When the water is hot, and with the power disconnected, feeling the tank may determine which Thermostat is stuck.

Depending how old they are, it may be a good idea to replace both (maybe the the other one isn't working at all ?).

Testing with a meter may give you more information (Thermostat ON / OFF, Element Good / Bad)

[58chevy]

Not sure I know how to test though I do have a digital MM. I have to move the water heater out of the way in a week or two for a new floor install. I was planning on doing any element work then rather that drain twice. I have heard all my life how guys say they can change the elements without draining but I never wanted to try it...model# check CD5 40 20RT973 0, I think that is a correction. Sorry about that error...and thanks for your help on this. I did read some of the posts on testing but I fail to understand them and I have trouble remembering electrical test procedures along with other repair work, mostly auto related.

[Icehouse]

Use your meter on the "Ohms" scale (upsidedown horeshoe)and with power to the heater turned off place the leads on each of the heater terminals.
No reading heater is open. Reading "infinity" (lazy eight) heater is good.
Now to the thermostats, test the same way but urn the control knob while doing so. It should make and break, if not replace them.
Keep the lower element set higher this will keep the water warm and uses less electricity then heating up from dead cold. :)

[58chevy]

Thanks icehouse...
breaker off top thermo at 200ohms read 19.8 doesn't really change when turned. element reads 6.6 ohms @200 ohm setting

Bottom thermo reads 3.8 to 9.....element read 0.00 or infinity as you said. I am thinking it's replace top thermo and element...does that sound right? the largest socket I have is 35 mm is that about right? Nut size on element.