I have a Carrier furnace model# 58GSC045-CB and the fan won't shut off, it runs continuously. This just happen when my wife turned the system on at our condo.
Any idea?

Will the heat work? If the heat is working check to see if the fan switch at the thermostat is in the ON or AUTO position. With this late 80s model furnace it will have a time delay circuit for the blower and the blower will get stuck in the on position and let the heat still work with the blower running all the time.

After I posted this I went and checked out to see if the heater was working and it's not. The system is set to "cool" as we're running the air conditioner but when I set it to heat the burners will not fire.
So to summarize:
- Fan runs continuously
- No heat.

Any ideas?

Will the heat work? If the heat is working check to see if the fan switch at the thermostat is in the ON or AUTO position. With this late 80s model furnace it will have a time delay circuit for the blower and the blower will get stuck in the on position and let the heat still work with the blower running all the time.

After I posted this I went and checked out to see if the heater was working and it's not. The system is set to "cool" as we're running the air conditioner but when I set it to heat the burners will not fire.
So to summarize:
- Fan runs continuously
- No heat.

Any ideas?