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gmay10
join:2012-01-08
Mount Joy, PA

gmay10

Member

Re: Gas Furnace not always turning on

I know it sounds weird and I have looked everywhere. I emailed the company my question and I am hoping to get a response today. I have taken the top and bottom panel off so I am not worried about doing it. There is also a piece of metal that is over the control board. I took that off a few weeks ago.

The furnace does not always go into lock down mode. It happens here and there. Yesterday it happened around 3 PM so I went down and turned it off and then turned it back on. It started up and didn't have any problems at all last night as I heard it come on a bunch of times in the middle of the night.

tp0d
yabbazooie
Premium Member
join:2001-02-13
Bulger, PA

tp0d

Premium Member

Intermittent fault sounds like a flame rod or an airswitch.

-j
gmay10
join:2012-01-08
Mount Joy, PA

gmay10

Member

I am about to go crazy!! I called the goodman company and they said that my model does not have a sight to see the blinking red light. Seh said that when that bottom panel comes off, it does nto reset the furnace. The light is pulsing which means everything is running normal. The thermostat says the heater is on. It is 62 degrees in here and should be 70. ANy thoughts. I justjust turned off the heater and that should reset it as I want to get some heat. But again, this only happens once everyweek or so. I am sure I would call someone to come out here to fix it and everyhting would be working fine!!
Thanks for all the help so far- I really appreciate it!
robo_geek
join:2007-08-09
Roswell, GA

robo_geek

Member

The simple gas furnace is pretty straightforward, there is the controller board, the gas valve, the pressure switch, some limit switches, an ignitor and a flame sensor. In most cases the controller board and gas valve are standard parts made by Honeywell.

If it runs at all, the controller board is probably good, and limit switches would also likely not make it not work at all.

In terms of 'failing to start' the top three things would be either the pressure switch is shot, the ignitor or flame sensor is cracked, or the gas valve is sticking (and needs to be replaced).

Normal startup is:

inducer fan starts, which opens big silver pressure switch (you can see small part move if operating properly). Pressure switch has Normally open and normally closed contacts to prevent somebody bypassing it with a jumper wire.

if pressure switch closes, then the ignitor should glow, followed by the pilot light ignition. (soft click sound)

if the pilot lights and stays lit, the flame sensor rod tells the main gas valve to open, and the main burners light. (strong click sound from gas valve).

If the inducer stays on foreever and there is no glow, then the pressure switch is where you start. Verify that pressure switch plunger is moving and measure if ignitor wires are getting voltage. Beware that pressure switch will not open if there is no good updraft, which can be very very fatal.

Also, the gas valve can just stick, so if the inducer is on, and the pressure switch is closed, then a gentle tap on the valve can sometimes get it to operate. Even if it's sticking, it will operate in correct sequence.

I might add that if any part is faulty, just replace it. Do not try to fix any of the parts or bypass anything. If the system is old, there also can be safety issues that can be very fatal, such as a rusted out heat exchanger or a blocked gas vent. Make sure the home has at least one CO detector, preferably two.