Tip & How-To about Heating & Cooling

Heater check out list for heater failures

Almost all furnaces built after 1978 have intermittant type pilots.
Ca banned them requiring electronic spark or hot surface ignitors, followed by induced draft motors, pressure switches or centrifigal switches that "prove" a induced draft exists, allowing the pilot sequence to commence.
electronic spark type units have a high voltage low amperage spark that is AC. Fire rectifies electricity that passes through it meaning AC becomes DC ! Fire is a terrible conducter however as a result , the DC signal is only milliamps/volts signal strength. the DC prescence is proof a flame exists for pilot, and safe to commence to mainburners.

As long as pressure switches stay closed, safeties and limits stay closed
and the DC signal to the ignition module is not broken, the furnace will run.

The normal sequence of operation is upon a call for heat from the thermostat a 24 volt signal is sent to W white (heat circuit) at the low voltage terminal board on furnace.
from there depending on unit and age the heat circuit may include a circuit board, but it still has the typical limits and safetys reqired for operation
its just not using electromechanical relays to control fan and induced draft motor etc.

for the induced draft to begin ,all limits, safetys in heat circuit must be closed.

induced draft begins and a proving switch, either pressure or centrifigal close allowung the pilot to begin, a spark or hot surface ignitor is energized and a pilot flame established,modern types use flame rectification to prove a flame, older Carrier, Payne,types have a 3 wire switch in the piloyt assembly that is a bi metal that expands and contracts clicking open and shut, allowing pilot or main burners, depending if cold or hot.

pressure switches are attached with tubing to the induced draft wheel housing and sense pressure differential and close upon induced draft running, the orifices that the tube attaches to on induced draft housing often plugs or is restricted causing pressure switch to fail to close, or waver on open and close , open , close, .

if you can run the fan in the on postion , you have both high and low voltage to the furnace.

if you dont have fan control check power, breaker , fuses.

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how do you light the furnace of a goodman ez 1625


We have not lit pilot lights ourselves since 1978 when they outlawed standing pilots in Ca for furnaces. We have electronic ignitions of spark oror hot surface ignition, neither of which can be manually lit.
Do you get any fan action if you flip the fan on from auto?if so, you have power and 24v control power too, I would start there.

Oct 31, 2012 | Goodman Heating & Cooling

1 Answer

where is the pilot light located on the furnace?


Depending on what kind of furnace you have and how old it is, you may not have a standing pilot. Newer furnaces use electronic ignition systems. Hot surface ignitors and spark ignition.

Feb 05, 2011 | Heating & Cooling

1 Answer

heater doesn't come on?


The electronic ignition system in a gas furnace is a modern development that allows more reliable performance than standing pilot furnaces, provides energy savings and contributes to better furnace efficiency (AFUE). With a standing pilot, found most commonly on older low efficiency furnaces (55% to 65% AFUE is not uncommon), a small gas flame is always burning and is known in the lexicon of American home repair as a "pilot light". The problem with this type of "analog" ignition is that it wastes energy by constantly burning gas and can sometimes be unreliable. These issues have led to the development of electronic ignition systems for mid to high efficiency furnaces that exceed the U.S. government's established minimum AFUE rating of 78%. The electronic ignition occurs typically in one of two ways:
  • Intermittent Pilot, or
  • Hot Surface Ignition The intermittent pilot system uses an electronically controlled high voltage electrical spark to ignite the gas pilot and then subsequently the main burners, when the thermostat calls for heat.
    The hot surface ignition system uses an electronically controlled resistance heating element not unlike a light bulb filament (and shown in the photo above), to ignite the gas burner.
    It is important to understand some of the other components of a modern furnace that you will encounter depending on the type of high efficiency furnace you have. Why? Because they can also come into play in repairing an electronic ignition furnace when it won't run properly. Let's take a quick review of the types of furnace designs and components found in high efficiency furnaces using electronic ignition.
  • Nov 14, 2010 | Goodman GMS90703BXA Heater

    1 Answer

    how to light a American Standard furnace


    If it is an old furnace with a manual pilot light there are pilot lighting instructions usually on a door or panel. If it is 15 years old or newer it probably has either a spark ignition or a hot surface ignitor. These can't be lit manually. If they fail they usually require parts to be repaired.

    Jan 01, 2009 | Heating & Cooling

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