We just installed a Honeywell Thermostat on our Trane heating system/heat pump circa 1988. The system comes on for about 20 seconds, turns off, comes on again for about 20 seconds and turns off, then it will come on shortly thereafter and stay on for awhile. We had a professional hook up the thermostat and he didn't mention that it was or wasn't compatible. Please Help.

((We had a professional hook up the thermostat and he didn't mention that it was or wasn't compatible))

The professional did not finish his job. He needs to adjust the thermostat or find the problem.