Hello
I had the same problem, turned out to be an airlock in the system. I bought a pcb and didn't need it. so if you want one cheaper than parts center price 95.99p + Vat then contact me scubaernie@btinternet.com I will let you have it for £89.00p including VAT + postage
Regards
Ernie
Ernie Stammers, January 2007