Air and heat unit which has auxillary heat too; when unit clicks on, outside unit fan starts; after delay, some other motor starts (if it was needing air, I'd say the condenser is struggling to start) tho sluggishly; wall Honeywell thermostat says 'heating' but no air ever comes thru the vents to heat our home. It smelled like something burning at 4am (but no smoke or specific site found for this smell). we turned it off. (May be of significance or not, altho we've had colder nites lately, it seemed to me that our unit ran nearly all the time; I'd be awakened for some reason and notice how it's running-- and wait, wait, wait until it shut off; but before I'd fall back to sleep, it would already be running again (and heating/blowing); I just thought it might be due to colder outside, but it did seem excessive.

Heating & Cooling - Gibson