Hi have been reading the various posts for a couple hours now. When my Goodman GMNT-080-48 forced air starts up, all appears well on start up sequence ; blower runs and igniter heats up and then turns off. Blower never comes on and the heat never seems to get going full. The little red light stays solid the entire time. I have read some people said the sensor needs to be cleaned. Does this sound right and if it does, is there a diagram to show me where it is? Thanks in advance. -Tim

If the gas valve never opens, it could be bad. Check to see if it ever gets power to it. If it gets power, and doesn't open, it is bad. A bad sensor will shut the gas off again after it comes on.

Any advice as to how to check for this? Thanks -Tim

To do simple checks like this you do need some tools. A test light, a meter, or a voltage detector might be the best place to start with. I came across the niftiest gadget for trouble shooting, a voltage detector. They work through the insulation of wires. There are several brands. I have a GB Instruments GVD-505A, less than $15 at Home Depot. Touch it to a hot wire, and the end glows red. Find the doodad that lights it on one side, and not the other, and you have the culprit. You do not have to open up housings and expose electrical contacts. You are looking at where your hand is, not where the meter is. Most people are capable of doing repairs and will get it going and not get hurt if they use a little sense. The voltage detector makes it even easier.

The voltage detector I have could just be touched to the wires to a 24 volt AC gas valve to see if it has power. It doesn't detect DC.

Most Gooman furnaces have safety devices such as rollout limits or a pressure switch in series with the gas valve, check to see if these are getting 24 volts in and out all the way to the gas valve.