Our thermostat has capability to program for 4 "zones" or times. We have cleared zones 2, 3, & 4 and only wish to use zone 1 for A/C. When reducing the temperature setting in zone 1 below the actual temperature in an effort to get the A/C to kick in, the thermostat will revert to Zone 4 (by itself) and turn the A/C off.

How can this be stopped?

Abandon the programming mode and use the hold feature