Ariston Water Heater With No Hot Water
On this page (5 sections)
The Short Answer: When an Ariston electric tank goes cold, the cause is usually one of four things: no power reaching it, a setting or mode that stops heating, a high-limit safety that has tripped, or a failed heating element or thermostat. The first two are owner checks. The last two are behind the cover, next to live terminals, and need a technician, who will also find out why the safety tripped.
Is it really no hot water?
Before looking at the heater, narrow down the symptom:
- Every hot tap is cold. The heater is not heating, or is not getting power.
- Only one tap is cold. Check that tap’s mixing cartridge or any thermostatic mixing valve on the heater outlet.
- Hot water comes briefly, then turns cold. A small tank may simply be empty after use, or the element is not keeping up.
- The heater’s indicator light is on but water is cold. Power is reaching the heater; the problem is likely the element, thermostat or a setting.
Owner checks
- Power. Many compact Ariston tanks plug into an outlet. Make sure the plug is fully seated, press the reset on the outlet’s GFCI if it has tripped, and check the breaker. Reset a tripped breaker once; if it trips again, leave it off.
- Water supply. Open a hot tap. If it sputters or runs weak, the tank may be partly drained or the supply valve closed. Never restore power to a tank that is not full; running an element in air destroys it in seconds. See water heater turned on without water.
- Settings. On models with a display, check the temperature setting and that no holiday, eco or timer mode is holding heating off. On models with a dial, check it has not been turned down.
- Any code or warning light. Write it down and check your model’s manual.
- Signs of water. If water is on the cover, under the heater, or dripping from the relief valve pipe, turn the heater off and deal with the leak first. See Ariston leaking from the front panel.
Likely causes the technician will find
| Finding | What it means | Typical repair |
|---|---|---|
| High-limit safety tripped, element and thermostat test good | A one-off overheat, or a thermostat starting to fail | Reset, then monitor; thermostat if it repeats |
| High-limit tripped, element shorted to the tank | The element kept heating and overheated the water | New element and usually thermostat |
| Element open (no continuity) | Element burned out, often after running dry or from scale | New element |
| Thermostat not switching | Control failure | New thermostat |
| Burned or discolored wiring at the terminals | Loose connection overheating | Wiring repair; check for water entry |
The technician isolates power, confirms it is off, and tests the element and thermostat against the ratings on your model’s label. Compact Ariston tanks use lower-wattage elements than full-size tanks, so test values and replacement parts must match the model. If the high-limit safety has tripped, a good technician treats that as a symptom and looks for the cause before resetting it. Our guide on why you keep having to reset a water heater explains the common ones.
Repair or replace
An element or thermostat is a routine repair on larger tanks. On a compact under-sink unit, the visit and parts can cost a large share of a new heater’s price, especially if the tank is several years old or shows scale or rust. If the tank itself is leaking, replacement is the only option. For other Ariston problems, start with the Ariston troubleshooting guide.
Frequently Asked Questions
Q: My Ariston stopped heating right after I drained it. Why? A: If power was on while the tank was empty or partly empty, the element can burn out within seconds and the high-limit safety may trip. Refill completely, then have a technician test the element before restoring power.
Q: Why does my small Ariston run out of hot water during a shower? A: Compact Ariston tanks hold a few gallons and are designed for a sink. They are not sized for showers, and the recovery time after emptying is measured in tens of minutes.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- A. O. Smith: standard electric no-hot-water diagnostic chart (opens in a new tab)Professional diagnostic context for standard electric storage heaters; not instructions to open or test your appliance.
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