A Class - not much hot water! PLEASE HELP!!!

Hi

I have a Pulsa Coil A-Class in my rented flat, the pulsa coil only produces enough hot water for one person to have a 5-10 min shower and then the water runs cold! This means that i am having to run the unit on boost most of the time which is a pain and even when on boost the water does not last long anyway.

The lanlord has sent someone out twice to fix the problem but as yet it has not been fixed, could you please advise and also could you let me know what the cost would be to fix it so i can pass it on to my landlord

Thank you

Phil Smith
(Bradford West Yorkshire)

also i forgot to say that a flashing red light (once a second) appears on the front of the unit after hot water has been used for 5 mins