A/C, heat pump, and "auxiliary heat" (light, circuit, cold)

[Bass101]

Hello,

It is about 85 degrees out and my a/c has been on as it has been all summer. I have been noticing that when the a/c shuts off because it's reached the temperature I've set it at the green auxiliary heat light on my thermostat (old school kind) comes on. Not only does it come on but it also flickers. But while the auxiliary heat light comes on the a/c is not running at the same time.

What could this possibly mean?

A/c seems fine otherwise. I just had the heat pump serviced for routine seasonal maintenance at the end of April.

Thanks!

[MrRational]

I don't know nothin' 'bout no green lights.... but NOTHING related to the heat functions and especially not the auxiliary heat functions should be coming on when your in the a/c mode.

maybe someone who knows more about heat pumps than I do will have more info...
but my gut is that something isn't right either in the t-stat or down below on one of the boards.
---

as to the a/c mode... the system is designed to 'cool' the air not make it cold

[chet everett]

My best guess is that you have a CRAZY old thermostat, like from back inn the Carter era or so. The way those type thermostats communicated back to the heat pump was all based on a couple of low voltage relays. The surge that occurs in the circuit probably "fools" the indicator light into coming on.

[Bass101]

The house is built in 1986, so it is probably the original thermostat. Is the aux heat indicator light coming on something I need to worry about? I don't feel heat coming out, and the blower is not even on. Just the light. Sometimes as the same time as cold A/C is coming out.

[MrRational]

time to invest a few pennies into the home.
buy a new t-stat (for $33)... it even has setback programming