Thermostat

cderas2 · Tue Mar 15, 2011 8:37 am

The heater comes on even though I have the thermostat on off, so I have to shut the heater off manually. I have an old thermostat with the mercury bulb. My home is a 1990 Redman 24x52 do I need to replace this old thermostat? or maybe the heater is bad and thats why it comes on.

Thanks
Chris-

Greg · Tue Mar 15, 2011 10:51 am

I would start with the thermostat, it's the cheapest & easiest.

Is the heat coming on or just the blower?

Greg

cderas2 · Tue Mar 15, 2011 11:29 am

Just the blower comes on with no heat, just air. I will change out the thermostat and respond back with results.

Thanks
Chris-

flcruising · Tue Mar 15, 2011 1:13 pm

A simple way to check thermostat is to disconnect it and switch the unit ON. (Spread the wires apart and tape if necessary.) If the blower turns ON then, you know it's not the thermostat.

cderas2 · Tue Mar 15, 2011 2:29 pm

I'm a female so I need to ask this question 'do I need to power off all the electricity in the house to disconnect the thermostat?

Thanks
Chris-

flcruising · Tue Mar 15, 2011 3:37 pm

Now I take it that when you said "...I have to shut the heater off manually.", you weren't referring to switching the breaker to the unit like I thought? You must be just switching the thermostat OFF?

The unit should have a disconnect either near it on the wall, or a breaker behind one of its panels. If you can't find either of those, there should be a circuit breaker inside your electric panel for the furnace.

cderas2 · Tue Mar 15, 2011 4:10 pm

I do shut the thermostat off manually, but then the furnace still comes on. It doesn't blow hot air its cold air and yes I do have to go take the furnace door off and switch it to off. I just don't want to get ZAPPED!!

Greg S · Tue Mar 15, 2011 4:57 pm

Easiest thing to do, and safest to start, is remove the cover from your thermostat. Turn the thermostat till the furnace starts and observe the position of the mercury bubble. Turn the thermostat to lowest position and observe the position of the mercury bubble. When the furnace turns back on if the bubble has not moved to the on position then it is not likely the thermostat that is the problem. I would guess if only the blower is coming on it is the temperature sensor in the furnace itself however I am not a HVAC specialist just a DIYer.