Heil gas, condensor furnace will not heat

[dj1100rt]

I have a Heil, gas, condensor furnace. Model #NUGK100DH3. Unit is a 1989 model.

As soon as I turn on the main switch to the furnace the house blower motor comes on.  Setting the 1993 Honeywell MagicStat 32 thermostat to heat, nothing transpires.  Gas is on.  Thermostat is programmed okay.  I temporarily turned up the temperature setting to be sure that it is demanding heat.  The display indicates that it is.

I checked the power up to the thermostat from the furnace transformer and it is 28.3 volts.

What do I look at next?

Dave

[ACtechGUY]

At the thermostat , place a jumper wire between R and W terminals. If heat comes on , replace the themostat.

If heat does not come on still, PLace a jumper at the furnace control board between R and W teminals. If heat comes on now , the problem is the wire between the heater and the furnace.

[Bobice]

Problem: Your furnace will not ignite the gas to produce heat for your home. When a furnace has a bad ignitor what I see most of the time is the following sequence of operation:

1. Thermostat calls for heat.

2. Draft inducer motor starts.

3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure produced by the draft inducer and closes.

4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small metal probe about 1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas.

Solution:You probably need to purchase and install a new ignitor. I would suggest that you inspect your ignitor closely for cracks. Make sure you do not touch the ignitor with your bare hands. If you do not visually see a crack, then you could have a furnace control board problem or a limit, rollout switch problem. The furnace's control board might not be supplying the voltage to the ignitor. If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you need to clean your flame sensor with light sand paper or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.