The overheat light comes on instantly I switch on at any temp setting and the water flows brilliantly but stone cold. Have cleaned the head, no joy. Should I be replacing something?

Tony, August 2009

Thanks to Roy (July 2017) we have saved £250.
Our Mira is 20+ years old but works fine until ... overheat light comes on even when running cold water.
Undo 6 screws, remove a bit of corrosion, put screws back - heh presto it works.
Only comment would be that you need a star screwdriver for the electrical screws and they are a little fiddly to put back - easy to get a cross-screw.
Thanks Roy
Paul - August-2021

Paul, August 2021

Thank you - fixed my Mira Sport with this issue in 30 minutes.

Jim, February 2021

Brilliant advice..!!
Thanks.

AP, March 2018

My Mira sport shower over heat light is on and the water is cold water pressure is good what should I do

Harry, September 2017

Followed the instructions above and cured the problem as sweet as a nut, many thanks for the advice

Martin from Halesowen, August 2017

Brilliant, it works. Thank you

Avis Lees, July 2017

Really helpful advice on here. Had same problem with overheat light coming on intermittently and shower running cold. Here's how I sorted it.

Isolate power at fuse board and switch.

Remove cover - 1 screw below and 2 at the top. Cover will easlily come off.

The thermal/tco unit sits on top of of the small tank. Very obvious.

Remove three connections. One to the left (brown). One to the right (brown) and lastly (because it holds the thermal unit/tco in place) remove the green connection to the front. I kept the wires and screws together by pinching with a bit of masking tape.

Lift the tco out (it simply sits on top). There was very obviously corrosion on top the tank below where the tco sits and corrosion at the sprung base of the tco. Carefully remove all corrosion back to bare metal and clean away debris (I used a clean dry ear bud).

Replace the tco and connect the green (holds it in place) and then both browns. Finally, replace the cover making sure no wires are trapped.

I always take a photo before starting the job. Now all good. If I can do it, anyone can.

Roy, July 2017

Hi there, my shower as of this morning has the overheat light on so subsequently the water is freezing cold regardless of what setting it is on. How can I fix it please without it costing me a fortune. Thanks :)

Shazza, December 2015

Guys thanks for the advice. I had a similar problem. 30 minutes and a bit of sanding later all is working well.

Craig Howorth, January 2015

Great stuff - same problem, found corrosion between TCO and heater unit. Scraped it off, all back to normal. Showerdoc's advice was replace the PCB - at over £100!

Mick, June 2012

same problem replaced the temp sensor on top of heater chamber !!!!!! hey presto fixed

wombles are weeee !!!!, June 2012

Chris your a star, same problem but after reading your post decided to remove the TCO and there was rust on the switch underside and on the copper connection where the TCO makes contact. Sanded both down to remove and now it works like new. Saved me a few quid and time. Thanks for your post

Dermo, July 2011

The TCO sits on top of the heating chamber. It is a normally closed switch and should have continuity across its contacts unless the water in the chamber overheats. I've just changed mine as the overheat light was coming on immediately and it metered open circuit. I replaced my switch and had the same problem? I had metered the switch as being open when in situ, but it metered closed when I had taken it out !! I took the replacement switch out and this also metered ok. On closer inspection I found a slight raised area on the top of the heater chamber due to rust. Once cleaned, the switch was re-inserted and all is now ok. I would recommend metering the switch, if it is open take it out and meter it again to check it is still open before buying a new switch.

Chris, June 2010

You need to check the inlet filter which will cause the overheat if it's in need of cleaning. If overheat comes on immediately sounds like the TCO (temperature cut-off switch) will need replacing. See http://www.showerdoc.co.uk/shower-spares/mira/mira-sport-10-8kw-1998.html

Derek, August 2009

Thanks. What does tco stand for?

Tony, August 2009

check the tco for power on both sides.

hi-spec plumbing & heating (essex), August 2009