Electric Hot Water Heater not working

At any time of the day, the hot shower lets you relax and calm down. This quiet moment turns awful when it turns into a cold shower… and not because someone else stole all the hot water. Why doesn’t the electric boiler heat up? You can pick up some clues with our diagnosis before calling in a professional.

Before working on your appliance, be sure to disconnect it from the power source.
Risk of electric shock.


To get started, check if the fault is not caused by an installation problem. Open a hot water faucet – if hardly any water is flowing, then there is a problem in the plumbing. Call a plumber to diagnose it. If the water runs, but cold or warm, then the problem will be electrical.


Look at your installation switch has not tripped, this would prevent the thermos from turning on. You probably have a switch that turns on your water heater during off-peak hours of the night? Try placing it in the forced position to see if your meter immediately marks an increase in power consumption. If this is not the case, the electrical problem comes from the electric boiler itself. If the circuit breaker trips again, there may be a water leak in contact with the electrical circuits, causing a short circuit.

Did you know 
To avoid too rapid corrosion of the tank, inside the tank there is a kind of rod called an anode. There are 3 different types of anode:

  • The magnesium (also called sacrificial) anode is generally used in areas where the water is slightly calcareous: then it will gradually dissolve to deposit its ions on the walls. Therefore, it is necessary to replace it after a while;
  • The anode is made of titanium (called current anode) using a low voltage, it will capture the minerals in the water (calcium and magnesium) to direct them to the tank walls. Therefore, it activates the elements naturally present in the water. It is indestructible and is effective in waters rich in calcium and magnesium;
  • The hybrid anode: it is in titanium and is coated with magnesium. It combines the properties of the two previous anodes.


Turn off the power supply to the water storage tank before performing this check.
Using a screwdriver, remove the cover held by a few screws, usually under the thermos. You will see the thermostat . In the thermostat you will see a small crack at the bottom of which we see a red button. With the flat screwdriver (isolated from electricity) try to push it.
If it wasn’t jumped, it was because the water heater was fine. This can sometimes happen after a thunderstorm, a power grid failure, or a hot water tank overheating. Then turn on the power (be careful not to touch the system under the water accumulator) and try to force again.
If it is activated again, it may be that:

  • the thermostat is defective and will need to be replaced.
  • Or even if the tank is too full of residue, you can activate the thermostat safety.


It is possible that the thermostat of the electric water heater is set incorrectly, or that the temperature control knob has been moved during a previous operation and that the setting is too high (too hot), inadvertently. If this is the case, turn the power off again, just turn the dial to lower the temperature and get the correct heating temperature, and turn it back on.
Still nothing? The thermostat may be faulty and should be replaced: to check its condition, use a multimeter in Ohms mode. Disconnect the connectors from the thermostat and place the probe tips (multimeter) on the usual thermostat contacts (most thermoses have a circuit diagram to guide you). If there is no continuity, you will have to change it.

Did you know 
The ideal temperature for a water heater to be set is between 50 and 60 ° C. Cooler, microbes could grow in the tank. Also, you would need to flush more of the hot water in the shower! Warmer, the temperature would favor the precipitation of tartar.


It is often necessary to empty and descale the electric water heater (when you notice that the water arrives faster or less and less hot). In fact, even at moderate temperatures, if the water is very calcareous, over time a crust will form and accumulate at the bottom of the tank and in the heater. So much so that you can no longer heat the water. It can also make the device unsafe.


If despite all this, the accumulator still does not work, the resistance is probably out of order. It can be verified with a multimeter. If you have one: disconnect all connectors from the resistor. Set up your multimeter. Place the two leads of the tester on each terminal of the resistor to check continuity (you should get a value).

Warning:  If the thermostat has burn marks, if the plastic has slightly melted or if it smells like burned plastic, it will be imperative (in addition to changing the thermostat) to replace the tabs or cut and re-peel. the power cord of your facility. Do not forget to tighten the screws of the new thermostat, otherwise the problem will return very quickly due to the heating of the electrical contacts.