Armstrong Air Ultra SX 80 Natural Gas Furnace

[gcbrinser]

My armstrong air ultra sx 80 furnace is not running right.  Upon a call for heating, the furnace comes on fine and the burners operate for about 20 to 30 seconds. Then the burners cut out. After a couple of seconds the ignitor relights the burners and they operate for about 4 seconds before cutting out again.  This cycle of cutting out and relighting goes on and on until the house reaches the setpoint temperature (which takes quite a while because the burners keep shutting off) and the unit shuts off.  During the entire heating cycle the fan and blower operate fine.  I've tried cleaning the flame sensor but that hasn't corrected the problem.  Any help would be appreciated.

[ACtechGUY]

If a furnace fires initially for longer than 5 seconds the problem almost always comes down to a bad control board.

You can try reseating / cleaning all connections at the control board , I once saw a similar probem due to corrosion at a connector on a carrier furnace( but this heater would not run for more than 5 seconds ever).

[gcbrinser]

Thanks very much for your reponse ACtechGUY. Would it be the ignition control board or the fan timer control board that I should replace? My guess would be the ignition control board, but I'm only an apprentice.

[ACtechGUY]

I hate to say it...... I just looked up armstrong. I figured it was just another furnace made by a big name and branded as armstrong. Seems to be a rather big player in the oil burner biz. We don't have oil burning heaters in the south. There is no telling what componets are in a furnace manufactured by an company used to making oil burner heaters.

Seems like it could be a different sort of critter than what I may be used to seeing.

Sorry

[gcbrinser]

I think it is a pretty generic natural gas fired furnace. The company is Armstrong Air which is associated with Lennox. It uses primarily honeywell internal components. there is a fan timer control module made by honeywell and an ignition control module also made by honeywell.

[ACtechGUY]

If that is the case then more troubleshooting is needed......

When the burners cut out, how long do they stay off? Oh wait can't read again..... I see they come back on right away.

You should clean or if needed replace Connectors to the spark module and also at the other end of the wire , like the connector at the flame sensor.) Any corrosion on the flame sensing circuit may cause this problem due to the tiny current that must be sensed via the flame. Also important is to check ALL ground connections (like at the gas valve, burner and spark module) including where the power enters heater.

[gcbrinser]

I tried checking and cleaning the spark module connectors, the flame sensors, and checking the grounds, but no success. Here is a video I took of the furnace operating. Should I start to replace parts? If so, should I start with the flame sensor, ignition module, gas valve?

[ACtechGUY]

Draft inducer. Pull the vent pipe off and check the inducer wheel. The fan is not creating enough vacume to keep the pressure switch made. Check the tube for leaks or bad connection . I see the tube kinda jumping around. It isn't supposed to move.

[gcbrinser]

I took the draft inducer off, cleaned it and reconnected the tube and it ran a full cycle without cutting out! Thanks very much for the help ACtechGUY.

[applianceman18007260692]

Nice observation AC

[CoolFish]

Was there any water in the pressure switch tube? you might checked for a plugged bleed vent hole on the pressure switch which might cause water vapor to condense to the hose.