At the on off button on the unit the blue warning light is flashing. Have taken cover off and pressed blue button to drain system. Also turned main electric supply on and off again. ?

Paul, September 2017

Manual here:

http://www.plumbcenter.co.uk/wcsstore7.00.816.246/ExtendedSitesCatalogAssetStore/images/products/AssetPush/DTP_AssetPushHighRes/std.lang.all/ti/on/Mira_AdvanceATL_Installation.pdf

Check this is definitely for your shower.

I can't reconcile your description of "blue warning light" with anything in the manual. Check from Page 20 onwards and see if that gives you any clue.

You may also get some info to questions posetd on this site:

https://www.showerdoc.com/mira-advance-atl-post-2003-shower-spares

Scroll down to the bottom of that page. You may find someone has asked about something similar already.

Acp, September 2017