We just had our AC repaired, it had a leak, but while the technician was here he said our thermostat needed replacing. So my husband installed a new thermostat, but now the AC will not turn on at all. He tried to put the old one back up but now that will not even come on. He reinstalled the new one, and we could hear clicking noise that sounded like the AC trying to kick on, but then it stopped and no AC. Please help!!