This is a troubleshooter for heating problems that cause you to have no heat in part, or all of your home, it also covers too much heat.
troubleshooter will cover oil fired boilers and furnaces and gas fired
boilers and furnaces.
The way this troubleshooter works is, there is a list of options, you select the option that best describes your specific problem or equipment.
You will be brought to another list of options and or questions, select the option or answer that best describes your situation, and so on, till you arrive at the cause, of your problem.
Please note: it is always best to have a licensed plumber, service your furnace and boiler.
There are too many possible scenarios to mention in a website, many of them can put your home and family at risk.
I do understand, that money is tight and plumbers are expensive, but nothing in your home is more dangerous, then your heating system.
The information given here, is intended to be a FYI, not a do it yourself guide.
Be safe call a professional.