My furnace is not igniting but the blower comes on and blows cool air.?

Question

My furnace comes on but it is not igniting-it uses gas as the fuel source-was told not to light it. I feel cool air and the blower is on. I checked my filter (I had replaced it last month and it had very little dust on it) but noticed my indicator was blinking. It read 4 flashes-open high limit switch. I own a RPJ II comfortmaker and I am unsure of what to do. I cannot afford to call a serviceman and want to know what it is, what's causing it, and can I honestly fix this myself. Any help is truly appreciated.

Answer 1

You really need the services of a qualified professional service technician. To begin you could temporarily bypass the high limit switch if that is the problem and see if the furnace will start. This could be very dangerous and possibly fatal. The safest and probably the fastest is to have a service tech work on it. The weak point on my unit is the HSI part and they are easily replaced once you get the part. Trying to light the unit when there is a warning against it could cause an explosion depending on the design of the unit. Trying to service any gas appliance without training is just plain dangerous and possibly fatal.

Answer 2

An open high limit switch is an easy job to fix. A sensor close to your burners has burned out, possibly from age.



It might look something like this:

http://ww2.justanswer.com/uploads/kentguidry/2010-01-09_203809_limit.jpg



Yours may have a reset button, in which case all you have to do is push the button. That may be all it takes.



If you can use a meter, you could first look on the wiring diagram to find all the high limit switches, then find them in real life and test them - infinite resistance means the switch is probably cooked and that's the one that needs attention. They're cheap and easy to replace.



If none of this made sense then drop back and call a tech. But before you do that, consider: none of my recommendations cost you anything, and the cost of the part is only a fraction of what the tech will charge you BEFORE HE EVEN DOES ANY WORK.



Good luck with it.

Answer 3

If it is gas and has a standing pilot the first thing you have to do is light the pilot. Whoever told you not to don't know squat about it. Be sure the gas is on. If it has an electronic igniter for the pilot you should hear a small ticking sound. That's the igniter trying to light the pilot. Get someone to look at it and see if the pilot is lit or will light - a friend or neighbor if you can't afford a service call.

Answer 4

If the high limit went, you may need to physically reset it, they just sort of pop like a bubble. That is what is keeping the heater from igniting. If you don't have a schematic or something, I don't know if you can identify where it is in the unit. Mine is in the top left of the fire box, four screws, pull it out, pop it, put it back in, see what happens, as well as the filters being clean, make sure that the returns are not blocked off.

Answer 5

if you were told not to light it i might guess its a DSI system (direct spark ignition) it runs off a circuit board most likely its defective and in the state of lock-out you'll need a pro to test the board last time i checked they run just over 100 bucks

Answer 6

/\Shorty gave you good advice.