I have a Furnace Model PG 100 HBM and SERIAL number is 77619. The blower is now running continuously. I am looking for a schmetic for this furnace. If you can provide me any information, diagrams and let me what could be causing this and what I need to do to fix this, your help will be appreciated.

Does your thrmostat have a switch marked ON/AUTO? I would not be overly worried about this condition, many folks set their stat to ON only. Does cost much more than when on AUTO and makes the home more evenly heated/cooled.

That I do not know, I have a ON/OFF switch with that I can turn the blower off manually but when there is no heat demand blower fan doesn't turn off automatically. That is the reason why I requested diagram so I can find out where that auto On/Off switch is, so I can replace it.

Thank you for your help

Is that switch set to ON or is it set AUTO?

I can't find the thermostat switch on the furnace... I have a one switch and that is for a blower. This switch is a simple ON/OFF switch... no marks on it

The thermostat I am referring to is likely on your wall, maybe in a main hallway. The ON/AUTO switch is most frequently a toggle which can be slid sideways from ON to AUTO and vice versa. Guide to Fan On Off Auto controls on air conditioning and heating thermostats (http://inspectapedia.com/heat/Thermostats8.htm)

Yes, I do have a thermostat switch, this switch is very old and it has one handle on the side with numbers like 30-40-50-60-70... If you turn this handle up heat comes on and if you turn it down heat turns off. Problem is when handle is down and cold air still comes out from the vents. I did not see any NO or Auto mark on that switch

The switch is on the side. Please review the attachment I provided in my previous post. The" handle" you are talking about is how you adjust your temperature

Guide you provided is for a newer switch. This does not help me. I have a older thermostat with a handle to control the temperature. What I need to know is if there is a auto relay installed on the furnace for a blower to come on and off automatically with a heat demand. IF yes then please tell me where this relay is located. That's all I need to know

I have attached a picture of my thermostat... please let me know if you can provide me a diagram that I requested