HELP PLEASE! I have an old Janitrol FHS90-25 natural gas heater that fan motor blows constantly. Don't know much about heaters. Removed access panel and can just see motor. Can't physically find limit switch and can I still get parts? Heater under house - very hard to get to. Just bought this house couple months ago. Had friend look at it said be better just to buy new one. Thanks.S:

Probably the fan switch. You need to find the switch and test/replace.

Also check the relay.

Do I just follow wiring to find switches - because don't see any through access panel... think I can still fins parts - heater about 20 yrs old?

You may have to use generic parts. If you do not know what you are doing I suggest calling a professional. They will also be able to make universal parts work where you do not have the knowledge. Safety first.

Follow the leads to the blower motor back to the relay that controls it. The relay will have wires running from its coil to the limit switch. Older furnaces had 2 limit switches. The lower limit switch closes when it gets warm sending power to the relay coil. It opens when it cools off. Either the relay or switch can stick in the closed position.

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.

I have a janitol ucs 175-55 gas furnace. Where do I light the pilot light?