Combi Boiler Does Not Provide Hot Water: 3-Way Valve Fault and Inspection

A technical service was contacted for an Ariston Cares Premium 24 EU2 combi boiler with the complaint that hot water was not coming from the tap. After the service inspection, it was stated that the fault was caused by the 3-way valve, and the problem was solved by replacing the complete part. The price of the part was also quite high.

My friend did not give me the faulty valve 🙂 so I thought this motor would not fail very easily and started inspecting the part. Below, I share the tests I performed and the information I obtained. I hope it will be useful to someone..

For those who want to get the job done quickly, first there is the 3-way valve cartridge removal video below, followed by the details…

Ariston Combi Boiler 3-Way Valve Removal Video

 

What Does a Combi Boiler 3-Way Valve Do?

The 3-way valve is a part in combi boilers that directs the flow between central heating water and domestic hot water. When the tap is opened, it directs the water to the tap.

3-Way Valve Fault Symptoms

• No hot water coming from the tap
• The water does not heat up even though the combi boiler appears to be operating
• Hot water fault warnings

3-Way Valve Structure in Ariston Combi Boilers

In the Ariston Cares Premium series, the 3-way valve system consists of two main sections:

• Mechanical valve body with a long seal
• Actuator motor operating with low voltage

While 3-way valve motors in some combi boilers operate with 220V AC, this model uses
a system operating with low-voltage DC.

Not a Stepper Motor: Electromagnetic Actuator

Although these motors are often called stepper motors, (I think because of the multi-pin connector on the motor) this is not technically correct. It is an actuator motor.
What Is an Electromagnetic Actuator? The structure used in Ariston combi boilers is of the electromagnetic actuator type. (I think it is also used in some Vaillant models)

Actuator Motor

• It converts electrical energy into magnetic force
• The magnetic force moves the spool inside the valve forward and backward
• The water flow direction is changed by this movement

Technical Information on the Actuator Combi Boiler Motor

The following information is found on the actuator motor I inspected:

• Model: UCE53N02D2GZ14
• Winding resistance: Approximately 90 ohm

In the measurements I made with a multimeter, I saw that there were two separate windings on the motor and that both measured approximately 90 ohm. This indicates that the windings are intact.

No value appears when measuring resistance on the middle pins. These terminals are the connections to the limiting switch (limit switch) that detects the position of the valve.

Note: Although they have a similar structure, the middle terminals may not be a limiting switch in different brands and models; you should take measurements

Actuator Motor Test Without the Combi Boiler Board

Tests performed without the combi boiler main board do not give a definite result, but they give an idea about the general condition of the motor.

1. Coil Winding Resistance Measurement

• The multimeter is set to the ohm range
• Both windings should show similar values
• If the values are equal, the windings are most likely intact

2. Trial with External Voltage

• A voltage between DC 9–12V is applied to one of the windings
• The voltage must be applied momentarily (not continuously)

These types of actuator motors do not rotate continuously like classic DC motors. The combi boiler board energizes the windings for certain durations and in a certain sequence. Therefore, do not expect it to rotate when 12V is applied directly.

The click sound coming from the motor at the moment voltage is applied indicates that the magnetic mechanism is operating and that the motor is most likely intact. Do not forget to bring the motor close to your ear to hear this sound.

Combi Boiler 3-Way Valve Fault and Mechanical Inspection

If hot water is not coming from the combi boiler, the mechanical valve section must also be checked, as well as the motor.

• Limescale
• Rust
• Dirt and sediment

These factors cause the valve mechanism to jam. The jamming problem can be solved with good cleaning, but the seals may also need to be replaced; I do not know whether its seals are available on the market. Although suitable seals may perhaps be found in an auto industrial area.

Fortunately, there are 3-way valve repair kits sold without the motor on the market.

The keywords you can use for part searching are: Brand model + 3-way valve repair kit meanwhile, this part is also called a new-model 3-way cartridge.

Conclusion from My Own Inspection

According to the tests I performed, I think the actuator motor was intact 🙂 However, the mechanical valve section was seriously jammed, quite rusty, and its seals were not in good condition.

The service discharged the dirty water by applying air through the combi boiler and then replaced the complete valve assembly.

I am not a combi boiler technician; however, according to the tests performed, I believe this fault could have been fixed by replacing only the mechanical valve section.

In my opinion, by evaluating the motor and mechanical section separately during fault diagnosis, unnecessary part replacements can be prevented. But services replace the complete assembly without offering this option..

As I said, I am not a combi boiler repairman (if my own combi boiler fails, I will take a look at it 🙂 ) it is up to you to apply the suggestions and methods I provided in the article. Be careful; if you do not have enough knowledge and experience, or if you are not sure, contact a service and do not take risks. A mistake you make on a combi boiler can be dangerous..