Testing Electric Shower Microswitches: The "No Heat" Diagnostic Guide

⚠️ SAFETY FIRST: READ BEFORE STARTING

Working on electric showers is dangerous. You are dealing with a high-voltage appliance (240V) and water.

• ISOLATE POWER: Always turn off the electricity at the main consumer unit (fuse box) and pull the isolation cord before removing the shower cover.

• VERIFY DEAD: Use a voltage tester to ensure no power is reaching the unit.

• LEGALS: In the UK, major electrical work in bathrooms is "Part P" regulated. If you are not a competent person or are unsure of these tests, stop and consult a Part P qualified electrician.

• DISCLAIMER: You follow these guides at your own risk. This site and its authors are not liable for any injury, loss, or damage caused by your repairs.

Before opening the unit, follow my [Electrical Safety Isolation Protocol] to avoid a 240V shock

Another easy job to do and these do go know and again even though they are usually high quality , best to replace with originals as they handles a fair amount of current so cheaper one could be a fire hazard.

Use you Multimeter on continuity with buzzer attach leads and listen for the buzzer.

to replace them you need to undo the wiring for the heater elements so be careful as to remember the correct order of fitment.

Why Microswitches Fail

Microswitches are mechanical switches pushed by the pressure plunger. They fail in two ways:

1. Burnt Contacts: High current (up to 45A) passes through these tiny points. Over time, they "arc" and the plastic melts, preventing a connection.

2. Mechanical Fatigue: The internal spring snaps, and you no longer hear the distinctive "click."

The Continuity Test (Step-by-Step)

1. Isolate Power: Turn off the main breaker.

2. Identify the Terminals: Most microswitches have three pins (COM, NO, NC). You are looking for COM and NO (Normally Open).

3. Test for "The Click": Set your multimeter to Continuity 

   • Place probes on the terminals.

   • Manually push the small button on the switch.

   • The Result: It should beep only when pressed. If it doesn't beep, or if it beeps constantly without being pressed, the switch is dead.

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before you take the front cover off set switch to stop position and note orientation of the switch 

its just threes screw to take the cover off and on off switch mechanism

Pull indicator light out of the way

undo all 3 screws

You will then gain access to the micro switches 

pull the top one of its mounting pegs and test for continuity 

if the multimeter beeps you know it working 

as you can see very low resistance so a good switch 

repeat of the lower micro switch 

and lastly the solenoid micro switch at the very bottom 

you can actuate it via the switch hole as per photo

close up of switch and multimeter connections for very bottom microswitch 

See our 2 videos on how to test the microswitches and the selector controls below