My timer has gone on the 4033 but i can still get HW and CH. what is the easiest and cost effective way of replacing this. Is it a case of just buying a new digital dual channel programmer? The thermostat motor etc all go into a wiring Centre so i assume i will not need to do any thing here. The back plate may need replacing as i have the mk3. All help will be appreciated. I am a competent engineer who is comfortable with electrics.