Mira K fault codewhat it means and how to fix it
Flashing yellow and blue with Start/Stop off, on the drain-pump variants. The shower and the pump transformer are not paired with each other at all.
Take care
What K means
Code K is the neighbour of code B and the difference between them is worth being precise about, because they sound the same and mean different things. Code B is a communication failure between two units that know about each other: the pairing exists and the link has dropped.
Code K is the absence of that relationship — the shower and the transformer have never been paired, or the pairing has been lost, so there is no link to drop. That distinction determines the fix. Re-establishing a dropped connection is a matter of getting the two back in range and letting them find each other. Pairing them is a deliberate setup procedure, and Mira add a second element to it that is easy to miss: their published action is to pair the units and ensure the dip switches on both units are correctly set.
Dip switches are small physical switches on each board that have to match, and they are set at installation. That points at when this code actually appears in practice. It is overwhelmingly a commissioning-stage fault rather than something that develops on a working shower — a new installation where the pairing was never completed, a pump or shower replaced individually so the new unit has never met the old one, or a set of dip switches that were changed or were never matched. A shower that has been working for years does not usually arrive at K on its own; if it does, something has reset one of the two units. That is worth saying because it changes who you call. This is more often unfinished installation work than a broken appliance.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Pairing never completed at installation | The commonest version by a distance. The shower works, the pump does not, and the setup step was skipped or interrupted. | Common |
| Dip switches not matching on the two units | Mira name this specifically. The physical switch settings on the shower and the transformer have to agree, and they are set by hand. | Common |
| One unit replaced without re-pairing | A new pump or a new shower has no relationship with the component it was fitted alongside until somebody establishes one. | Occasional |
| Pairing lost after a supply interruption | Rare on a working installation, and the reason a long-standing shower arriving at this code is worth a second look. | Rare |
What to try yourself
Establish whether the shower has ever worked with its pump. A new or recently altered installation that has never run points at unfinished setup rather than a fault.
Confirm the transformer is powered and its light is on, so you are not chasing a pairing problem on a unit that has no supply.
Follow the pairing procedure in the Mira guide for your model, and complete it rather than stopping when the lights change.
Have the dip switch settings on both units checked against each other. Mira make this part of the remedy, and mismatched switches will defeat a correct pairing.
The dip switches are inside the units. Isolate both the shower and the transformer at their supplies before anyone opens either, and leave it to whoever installed it if you are unsure.If the shower is newly installed and this will not clear, go back to the installer. This is a commissioning step rather than a repair.
Get a qualified electrician to look at your Mira K
We do not pass enquiries to a repair firm, so there is no form here. When you book a qualified electrician, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What it costs to fix
Typical repair cost
£0–£150
Time on site
40 minutes
Nothing if the installer returns to finish commissioning, which is the usual and correct outcome. A separate visit to pair and set the switches is the cost if they do not.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Mira fault codes
- BGet it checkedFlashing yellow, on the drain-pump variants only. The shower and the pump’s transformer have stopped talking to each other over their wireless link.Related: pump
- AGet it checkedFlashing red on the Status light. Mira group three water-supply problems under this one code: no supply, low pressure, or a blockage somewhere in the outlet.Related: same brand
- DGet it checkedFlashing red and yellow. The outlet thermistor has seen a temperature above what Mira allow, and the shower has stopped rather than deliver it.Related: same brand
- MUsually simple to fixFlashing white. Not a breakdown — the shower was switched off at the cord before it finished its shutdown, and it will not restart properly until it settles.Related: same brand
- LGet it checkedStatus light off entirely, with Start/Stop off. Mira call this an electrical fault and the action is to check power to the shower.Related: same brand
- FGet it checkedFlashing red and blue with Start/Stop flashing. The cold water arriving at the shower is already hotter than Mira allow it to be.Related: same brand
Own a Mira electric shower? Save it and its codes come first next time.
Related guides
Common questions about Mira K
What is the difference between codes B and K?
B is a link that exists and has dropped. K is no link at all — the two units are not paired. B is usually a range or power problem; K is usually setup that was never finished.
What are the dip switches for?
They are small physical switches on each unit whose settings have to match for the pair to work. Mira make checking them part of the published remedy, so a pairing attempt can fail purely because they disagree.
My shower is brand new and shows this. Whose problem is it?
The installer’s, in almost every case. Pairing and dip switch setting are commissioning steps, and a shower that has never run with its pump has not been finished rather than broken.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.