urgent: why my heating is not working

[smr]

Hi,

My heating has not been working for several hours this morning. The fan can still blow the air in, but there is no heat at all. I can hear the noise of working machine from my facility room.

What could cuase this problem? Please give me some ideas when you can.
Thanks a million.

[smr]

Here is my update for my heating system:

machine: DC90 ULTRA HIGH EFFICIENCY( HEIL ).
Testing procedure:
1. Turn on themometer and to 80 degree.
2. Go to facillity room, I found machine is rnning, but when I pull out the filter and put a paper into the hole to test the air flow, I found there is no air flow.
3. I think my furnace is using Gas. But I am not sure. Will I be able to see the Gas burnning if my furnace is indeed A Gas Furnace?

Any ideas?

[kactuskid]

There should be a power switch that's on the side or near your furnace. Open the switch. Now, make sure the filter is clean, also make sure the pipes that exhaust outside are not covered over with ice or snow, not blocked in any way. Now close the power switch again. I'm guessing the heater will work. The problem is, after it reaches the thermostate setpoint and stops, when it cools down again and the thermostat calls for heat, the heat may not come on again but the fan will continue blowing. If this happens then you need to call a service tech to come in and troubleshoot if for you. It could be alot of things then and you'll need his expertise to fix it.