No hot water using E7 element

Hi

I have a customer with a A Class who is having to use the boost to get hot water.
I Checked the elements and am getting 19ohms on both. I replaced the Relay and Base for the off peak element but this has made no difference.
I removed the incoming E7 supply cable and fitted a fly lead to a 13 mains socket to try and make the store think it was a on the E7 tariff but all that happened was the RCD continually tripped in the consumer unit.

Not sure if the PCB would cause this problem aby advise would be much appreciated.

Ken

Sound as if the heater is leaking current.
Try testing the other one using your same method.
If that is ok then the bottom heater is the culprit.