Before it even stats it will repeatedly ignite at 30 second intervals for about 12 times before starting.Then the heater will start up and after about 1 minute will turn off again It will repeat this process until the temperature level of the thermostat has been reached. After the thermostat level has been reached it will blow cold air though the ducts.
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Re: Starts and stops repeatedly
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Have you checked the diagnostic indicator?
Some possibilities are....
If the buner lights than rapidly goes out....You have a dirty flame sensor..... Remove the sensor with a 1/4" nutdriver. This sensor is located under the burners. It has "ONE" wire hooked to it. unplug the wire. pull ou the screw. Carefully remove the sensor. Clean it with a small piece of sandpaper. reintall. This should give you heat.
Pressure switch.....If the burner does not light. It can be a variety of problems. Check your flue pipe for obstructions.
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Typically it should glow for a full 30 seconds BEFORE power is sent to the gas valve to open. This is even after the 'pre-purge' sequence where the inducer starts and runs for a predetermined amount of time to purge the heat exchanger of any residual gas. The whole sequence can approach 3 minutes or more on some models.
Check all connections on the circuit board before assuming the board is bad.
If the unit has a induced draft motor on it it then it shoul turn on first when stat is calling for heat. If it does so then in about 30-45 seconds the igniter whether hot surface or spark should try to light pilot. If this is not happening then you probably need to replace the igniter. Hope this helps. Thank you
Replacing the board, flame sensor, and pressure switch, and cleaning out the induction motor was definitely a good start. Other things to check would be a blocked or restricted flue pipe, I have ran into a few bird nest before!, and you also want to check or replace the hose that runs from the inducer to the pressure switch if you haven't already. To be honest, most of the time I clear out the nipple on the inducer where the hose goes with a small piece of wire and it works. The last thing I would suggest is making sure the new pressure switch is rated for what you need. Alot of the revisions on furnaces actually call for less than the original pressure just for this problem. Hope this helps and good luck!
Are you sure that your gas supply is strong enough, and that being said is there an in line regulator on your installation? You need gas pressure along with volume to burn properly. The itself sounds fine it is going thru all of its system checks then shutting down. You need someone with a set of gauges and check gas line pressure then check past the regulator and again check the pressures. It could be as simple as opening the regulator up slightly or as costly as replacing the line with a bigger one to support the heater. Make sure that you have purged the line good, and I would do this at the dirt leg in the supply or as close to the heater as possible.
You don't mention make or model so here is my guess as to how to thinkout the trouble of what ever is in your attic.
For some reason, your heater is mis-firing. Normally, I would expect 3 to 5 such events at which time the heater goes out on safety. The heater knows it is on safety but you don't until it gets cold in your house. When you turn the power off, wait the 30 seconds, turn it back on, the heater no longer knows it is on safety (memory cleared) so it fires. Your heater continues to fire until ? at which time it starts counting again to 3 or some number. At the max mis-fire number - it goes out on safety again ... repeat - turn it off, wait 30 seconds, turn it back on - no memory and so forth.
Do you have a service contract or regular service man? Might be time to find one.
What usually causes that is the ignition component is not hot enough to sustain a hot enough temperature to keep the fuel burning some have a spark ignition some have a hot surface ignition,try replacing it and it should work fine.