[rummer]

Hi,

I have A Carrier Weathermaker SX furnace, model 58sx040-cc. When the thermostat calls for heat the draft inducer motor turns on, then the burner ignites. After the burner has run for about 30-45 seconds, the blower motor is triggered and comes on, but the burner and inducer shut off. Then after a minute or two the blower shuts off and the process is repeated.

If I turn the fan on always instead of auto at the thermostat, the furance will run until the thermostat reaches the proper temp. and shuts off.

Any ideas?

[hvac1000]

Brand of thermostat?

Exact model number of thermostat?

You are saying if you turn the blower switch to the on position that the furnace wortks normally and stays running till the set temperature is reached but if you leave the blower set at automatic the furnace short cycles?

That is a very strange problem.

I know what you are saying about the gas bills mine are high also.

[rummer]

Thermostat is a Hunter digital. Don't have extact model with me.

The answer to question is yes.
Furnace will short cycle if the thermostat setting for the fan is Auto. I have had the thermostat for 5 years and it has worked fine in the past.

[hvac1000]

It is a toss up?

I might have a look at the fan and limit first.

Post brand and model number or post a picture so I can see what type of unit is on the furnace.

[rummer]

The thermostat is a Hunter model is 44550. I don't think it is the thermostat, the thermostat is calling for heat. I thought it might be a control board or a pressure switch that is not working properly.