I have a thermostat that makes contact with an old style mercury switch that is in a glass bubble. Inside the glass bubble are two contact wires which, when contacted by the mercury, turn on the heat pump. The unit has an Aux Heat green light as well as a Emerg Heat red light. I have noticed that when the heat pump is started normally by the thermostat, that only one contact is touched by the mercury and the air coming out of the registers only reaches about 88 degrees after 10 minutes of operation. When I move the setting lever on the thermostat to increase the indoor temperature, the mercury switch moves farther and contacts the second contact which turns the green Aux Heat light (not the red Emer Heat light). This results in the air coming from the registers to increase to 110 degrees in about ten minutes.
What is going on here? I might be able to explain the extra heat if the emergency electrical resistance heater inside the blower was coming on, but I don't think that is happening. Can anyone give me some advice? Its cold in here.