Thermostat emer/aux heat not working

[p53]

we have a bryant 2-stage heat pump (at least 10 years old), and mechanical mercury thermostat with the usual manual switch for emergency/aux heat. both the heat pump & thermostat seem to be otherwise working fine. but the emer/aux switch that used to immediately and unfailingly turn on a red light when switched on, no longer is, and we can't detect it making any change in the heat. am not sure if the proplem is with the second stage on the heat pump itself, or the thermostat, or maybe even just the light bulb burnt out (it's sealed inside where I can't get to it). any ideas?

[hoar]

quote:Originally posted by p53

maybe even just the light bulb burnt out (it's sealed inside where I can't get to it). any ideas?

I had a light burned out since the unit was new.
Aux heat still worked when mercury bubble went on proper side.
I understand that thermostats almost never fail.

You could check functioning by looking for 24v ac on aux connection.
If you don't know how to do this, call someone who does.