Gas and Oil Home Heating Furnaces - no heat

My son say his unit won't heat, several months ago, he said he turned off the gas to the unit, using the outside valve. He thought the unit had a pilot-lite, it doesn't. I didn't think that could cause any harm.

This gas valve on the inside of the unit, has two wires going to it, according to the wiring diagram on the back of the panel, those wires appear to be switched, I don't know if that makes any difference?

That gas valve has a couple of allen screws in the top, I guess on the outlet and inlet sides of the valve. I thought about removing the inlet screw to see if gas was getting to the valve, I also thought about removing the outlet screw to see if the valve was letting gas through, but to do that I would have to turn on the controls to energize the valve, I'm not sure what the ignitor is going to try to do, while I'm doing that. I'm a little worried about that.

I tested the voltage to the unit, it has power. I didn't do any other testing, nobody was home.

Are there any safe tests we can do on this unit. I don't know the name of the unit, the tag was wore off. It is a heat and air unit, sits outside. I guess it has electronic ignition for the heater part, looks like a sparkplug wire going to the ignitor. Not sure how that works. thanks

the allen screws are adjustments dont mess with them unless you have the right gage to use to adjust the pressure. if it was working right last year it should this year as well with out moveing wires around . it sound like you just have air in line just turn heat on max start unit and let it try to start a few times to blow air out of line, if this dosnt work call a tech dont need to blow self up

The unit is a heat and air combo unit. They rented the house a few months ago, said the ac part worked fine, but the heat doesn't, they never tried the heat until recently. For all I know it never did work. I told him to call the landlord, but he thought the fix, might be something simple.

I don't have enough basic info on these systems to do any good. thanks

I told him to call the landlord, but he thought the fix, might be something simple.


For sure call him. Dont mess at all with the unit there. It all can be put on you that it dont work.


ED ;)

Right, I understand.

Just for my basic understanding. You request heat through the thermostat controls, then the ignitor, which is a heating element? heats up, then there is a sensor close by that detects the heat from the ignitor and signals the gas valve to open? Is that anywhere close? thanks

If he's renting, he should have called the landlord first and not messed with it. After all, it's really not his.

There is no sensor to tell if the ignitor is hot. It is all done on time. Stat calls for heat..X seconds later the ignitor is energized, ignitor warms for Y seconds...gas valve opens

There is a sensing element next to the ignitor. If that isn't a heat sensing element, what is it? The end of it almost feels like a thermocouple. I guess it senses heat from the main burner, it's my understanding, if it doesn't sense any heat for a certain amount of time, the gas valve will close?

It's also my understanding, that if the ignitor was the only problem, it is possible to lite the burner manually. It will work fine, until the heating cycle ends, then your right back where you started.

Since my son had trouble with that unit, it just caught my interest. I'm reading everything I can get my hands on, trying to understand the basics. thanks

The sensor is for the main burner, not the ignitor. If that sensor does not detect flame within the prescribed safety time, it will close the gas valve. Some systems lockout after 1 trial for ignition, some after x tries, some not at all (just keep trying).