Bob, you need to change the main module in the back of the machine. We stock it at £56.28 + £6 postage (exchange). This is ready programmed for your model number. To order, go to our website at www.emwelec.co.uk and put WF620 in the search box or call us on 01159652118. You will still have the option of returning the module within 14 days for a refund (less our handling of £12) if it does not sort out the problem. Tony EMW Electronics
Tony, June 2015
