Low voltage on water heater

[Bible9230]

I am having trouble with my electric water heater. I have a suburban SW6DE. I have pulled off the switch and measured the voltage. I am plugged into shore power but I am only getting about 15V. Any ideas on why the voltage is low?

Matthew

[Pull Toy]

My first suspect would be your volt meter. Have you tried any of your outlets? If it is a multi meter, there are several different scales. If your outlets are also reading 15 volts, your meter is not set right.

If you still have low readings on just one breaker, I would unplug from shore power and check my grounds. You can also swap breakers from another circuit, and see if the problem follows.

[SADLY]

have you verified with a wiring diagram what voltage you should be finding at the point you're measuring?

The control board for the water heater runs on 12v - regardless of whether you're plugged in to shore power or not... OR heat source selected (gas/electric)....

just because it's tied into your 120v electric heat switch, doesn't mean you might be measuring a spot that powers a 12v relay.

[hankpage]

Check to see if the circuit breaker and the switch on the heater are on. On a digital meter set for ac volts, 15 may just be a false reading. What switch are you talking about ..... the switch for operating on gas is 12v dc.

[Bible9230]

I get 110 at the socket, so the meter is good. The diagram says that I should be getting 110 at the switch. I am measuring across the connections that plug into the back of the electric water heater switch outside by the heater. The circuit breaker and all known switches are on.

How do I move and check at the breaker to see if the problem follows?

Matthew

[bobbecky]

What you are doing is checking the same leg, in and out, instead of checking that leg to the neutral. You need to gain access to the neutral, which will be present at the terminals of the heat element. The white wire will be the neutral, which is not switched, and the black wire is the hot, which is fed through the switch where you are attempting to check voltage. You can put one lead on the neutral connection at the element and the other on the lead at the switch where you are trying to check for 120 volts. With your digital volt meter, you are getting a false/phantom reading the way you were trying to check for power.

[Bible9230]

Yes, I was checking it incorrectly. Going from the black switch wire and the white wire on the rear of the heating element, I was able to get 115v. I reassembled the switch and put it back in place.

With the switch on, I get no voltage on the rear of the heating element. The troubleshooting guide says to check the thermostat switch. I cannot figure out how to do that.

Matthew

[bobbecky]

It will probably be easiest to just replace the 120 volt thermostat/high temp limit switch. Amazon has them for $12, Suburban part number 232306. If the switch is working, and disconnected from the wiring, with an ohm meter, and the reset button reset, you should have continuity across the two terminals. Just make sure you are checking the 120 volt thermostat, and not the 12 volt one, which is a different part number.

[Bible9230]

I replaced the 120v thermostat and that solved the problem.

Thank you everyone for your help!