Came out to perform preventative maintenance on heat pump system. Discussed with customer about maintenance being provided, filters, and any issues. Customer stated that he had filters of his own he wanted installed, and also let me know that the emergency heat works only with the heat pump on, but said it’s been like that since he moved in and it’s been fine. I inspected the blower assembly, motor, capacitor, electrical components, heating elements, evaporator coil and overall condition of equipment. Blower assembly has a little build up on it, and evaporator coil is in good condition still. Cycled heat pump on and checked operation, amps, temperatures and pressures. Advised customer that it’s most likely his thermostat that not allowing the emergency heat to operate on its own. Customer isn’t interested in doing anything about it, and wants to leave as is. Will look into having the blower assembly cleaned next service.