Digital Shower Not Working (Aqualisa HiQu, Mira Mode, Grohe Sense)
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →Digital shower ECUs are mains-powered and located near water. Do not open the ECU unless you are a competent person. Many digital shower faults require the manufacturer's engineer or a qualified electrician.
Digital showers have become increasingly popular in UK homes over the past decade, offering convenience, precise temperature control, and smart home integration — but when they stop working, many homeowners panic. The truth is, most digital shower faults are straightforward to diagnose and often don't require expensive engineer callouts. The key is understanding that these systems split the clever bits (the electronic control unit) away from the shower outlet itself, which means the problem is rarely the unit you're standing under. This guide walks you through the most common issues — dead power supplies, loose cable connections, temperature sensor faults, and app connectivity problems — so you can either fix it yourself or speak confidently to an engineer about what's actually wrong. If you're uncomfortable working near mains electrics or water, or if the fault persists after these checks, a Gas Safe registered engineer or the manufacturer's technical team is your best bet.
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Most likely cause & what to check
Understand how a digital shower system works before troubleshooting. A digital shower has three components: (1) a remote-mounted Electronic Control Unit (ECU) — a box typically in the airing cupboard or under-floor void, plumbed to the hot and cold supplies; (2) a control/outlet unit in the shower enclosure — this contains only the UI electronics and a solenoid, with no heating element; (3) a low-voltage cable running between them. The Aqualisa HiQu ECU has a distinctive white plastic housing about 30 cm × 20 cm; the Mira Mode ECU is similar; the Grohe Sense uses a different topology but the principle is the same. Always start diagnosis at the ECU.
No response at all — no lights, no beep, no water: check the ECU power supply first. The ECU should have its own fused spur or MCB in the consumer unit — check it has not tripped. On Aqualisa HiQu, the ECU has a green LED on the front when powered; if it is off, the power supply has failed. On Mira Mode, a solid blue LED on the ECU indicates standby. Use a non-contact voltage tester at the ECU's mains terminal block (with the cover on, most ECUs have an LED visible without opening). If power is confirmed but the ECU is dead, the ECU itself or its internal fuse has failed — contact Aqualisa (01959 560010, aqualisa.co.uk) or Mira (01242 221221, mirashowers.co.uk) for ECU replacement. ECUs are often available reconditioned for £80–£150.
ECU powered but shower outlet not responding — communication fault: the low-voltage cable between the ECU and outlet unit is the most common cause. Check the cable connectors at both ends (ECU and outlet unit) are fully seated — they can work loose, especially in timber-framed buildings that move seasonally. On Aqualisa HiQu, the outlet unit connects via a 6-way DIN-style plug; on Mira Mode it is a proprietary multi-pin connector. Inspect the cable along its run for damage (especially if it passes through joists — a nail or screw through the cable is a known installation error). A flashing or unusual LED pattern on the outlet unit usually indicates a comms error — Aqualisa and Mira both publish fault code guides in their installation manuals, downloadable from their respective websites.
Temperature not reaching the set point — digital shower running lukewarm: the ECU controls temperature via a mixing valve (an electromechanical actuator on a thermostatic valve inside the ECU). If the ECU is receiving power and the outlet is responding but water is not reaching temperature, the thermostatic actuator or sensor inside the ECU is at fault. On Aqualisa HiQu and Mira Mode, an error code will typically be displayed on the outlet unit — for example, Aqualisa shows a flashing 'H' for a high-temperature fault. Before calling out an engineer, check that both hot and cold supplies to the ECU are open (service valves turned fully anti-clockwise) and that the hot supply is genuinely delivering hot water (run a nearby bath tap to confirm).
Grohe Sense digital shower — no flow or error code on display: the Grohe Sense is a different architecture where the valve unit is wall-mounted in the shower but the electronics are integrated. Error codes are displayed on the unit's digital display — Grohe publishes a full error code table in the installation manual (downloadable from grohe.com). Common errors include E1 (temperature sensor fault), E3 (no hot water detected), and E5 (flow sensor fault). For E3, verify the hot supply — Grohe Sense requires a minimum 1.5 bar on the hot inlet. For E1, the temperature sensor is replaceable by a Grohe-authorised engineer. Contact Grohe UK technical support: 0870 240 2777.
App-controlled digital showers (Mira Mode, Aqualisa HiQu+): if the app has lost connection to the shower, first check the Wi-Fi bridge or hub (if fitted) is powered and within range of your router. On Aqualisa HiQu+, the smart module is a separate device that plugs into the ECU; on Mira Mode, the Wi-Fi is built into the ECU. Perform a factory reset of the app connection (instructions in the app Settings > Shower Management > Remove) and re-pair following the in-app guide. Ensure your router is broadcasting on 2.4 GHz — neither system supports 5 GHz Wi-Fi. If connectivity issues persist after re-pairing, update the shower's firmware via the app if offered.
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Frequently asked questions
Why has my digital shower stopped working after a power cut?
Power cuts often trip the dedicated MCB or fused spur protecting the ECU. Check your consumer unit and reset the breaker — this solves the problem in the majority of cases. If the breaker trips immediately after resetting, the ECU itself may be faulty and will need replacement.
My shower outlet lights up but won't turn on the water — what's gone wrong?
This is almost always a communication fault between the ECU and the outlet unit. Check that the low-voltage cable connectors are fully pushed in at both ends — they can work loose, especially in older timber-framed houses. If they're seated properly, the cable itself may be damaged, particularly if it runs through joists where a screw or nail could have punctured it.
The water comes out but it's only lukewarm, even though the ECU is powered and responding?
The mixing valve inside the ECU controls temperature, and if it's not reaching your set point, either the thermostatic actuator or the temperature sensor is failing. Before calling an engineer, confirm that your hot water supply is actually hot by running a nearby bath or basin tap — if that's cold too, you have a boiler or supply issue, not a shower fault.
Can I open the ECU myself to have a look inside?
No — digital shower ECUs are mains-powered electrical units in close proximity to water, so opening them carries serious risk of electric shock or causing permanent damage. Unless you're a qualified electrician, contact the manufacturer's technical team or arrange a qualified engineer visit. This is a safety boundary well worth respecting.
My app says the shower is offline — is it broken?
App connectivity issues are separate from the shower working physically. Check that your Wi-Fi hub is powered and in range, and confirm your router is broadcasting on 2.4 GHz — smart showers don't support 5 GHz networks. Try removing the shower from the app and re-pairing it fresh, and check whether a firmware update is available.
How much does it cost to replace a faulty ECU?
Reconditioned ECUs typically cost £80–£150 from the manufacturer, which is significantly cheaper than a new unit. Labour for fitting usually adds £100–£200 depending on your location and plumber's rates. Always get a quote before committing to the repair.
What's the difference between a digital shower and a normal thermostatic shower?
A thermostatic shower mixes hot and cold water using a mechanical valve in the outlet unit itself. A digital shower uses an electronic control unit remotely located (in the loft or airing cupboard) to drive a motorised mixing valve, which allows for precise temperature setting, memory functions, and app control — but it's also more complex if something goes wrong.