the burner on my furnace won,t light the pilot light will light off of the igniter and both will go out?

Question

it is a lennox cosavetor 3 also the sensor gets glowing red

Answer 1

Sounds like a flame sensing problem. Hot surface igniter (HSI) glows, pilot holds for about eight-seconds, then drops out. Usually retries three times before going into "lockout". There should be a rod that sticks up into the area of the pilot light. On pilotless systems, the flame sensor is at the far end of the burners from the igniter. Chances are that the flame sensing rod dirty. Carefully remove the pilot assembly and clean the flame sensor.

If your furnace is equipped with a "smart valve" to control the gas, then you probably won't be able to clean your sensor. If your pilot assembly has one thin blue lead going into the sensor, and two black leads going into the igniter, the pilot assembly (Honeywell Q3400-A) is so small and fragile that you stand a good chance of breaking your igniter in the process. Occasionally, the igniter will double as the flame sensor, in which case you may have to replace the igniter.

The only time that a flame sensor needs to be replaced is when there is physical damage to the component. The way that it can be checked is by seriesing a multimeter, set for uaDC, into the sensor. Anything in the 0.8 microamp or less range, and typically a good cleaning will bring it back up to 3.5 ua. Any furnace that uses flame rectification must be properly grounded- this usually leads more to intermittent problems, but it's a good point to add, as most service technicians don't even know it. If the microamps check okay, the gas valve or ignition module usually needs to be replaced.

If you have any uncertainties about your safety, or that you won't be able to put back together what you are taking apart, it is best to just call a service technician. I have often seen the DIY'er who cost themselves more time and money than they would have needed to spend by calling a professional first. Also if it starts becoming to much of an ordeal, consider what your time and your family's comfort is worth.

If this doesn't help, update your question with a more detailed description of the symptoms. Best of luck!!!

Answer 2

HI Mike, it seems that you've got gas coming through the valve as evidenced by the pilot staying lit. So the problem is on the demand side of the furnace, which could be one of 3 issues. From least to most expensive here they are: 1. The Flame sensor is carbon coated, clean it off with steel wool. This part has a ceramic sleeve over a wire and sits in a bracket where the pilot heats it. If the pilot lights but the burners don't kick on, this is probably the culprit. 2. The thermocouple, an aluminum tube that runs back to the gas valve from the burner may be bad. 3. Pressure Switch is bad, have found this on Ruud furnaces. 4. The gas valve is failing to open when demand is called for which leads to number 5. 5. The "brain" or ignition module control board is not working correctly, there is sometimes a reset on the board that you can use, most have to be replaced, Good Luck!

Answer 3

Somethings wrong.

The burner ignition is blowing out the pilot and the burner.
Does it go "wooof" when it does it?

Do you know how to make a cat go "woof"? Gasoline and a match.

I would guess that it's not lighting as soon as it should be, letting a little extra gas build up, and blowing itself out.

Almost sounds like it's not getting enough gas.
That's make it slow to light AND easy to blow out.

Check to make sure the main gas and the valve to the furnace are both all of the way open. Usually if the valve "handle" is aligned straight with the pipe, it's on.

Are your other gas appliances OK?
Natural gas or LP? I was thinking maybe you got a bad load of LP...

I dunno, but now's not a good time to not have a furnace - at least not here in Missouri.

That's all of the ideas I have.
Hopefully you'll get some better ones and can figure it out.
Or, call a repairman.

Answer 4

flame sensor is probably bad.

all gas appliances need to "prove" a flame before main gas is allowed to come on.

generally this is a THERMOCOUPLE it should be roughly at the tip of the pilot flame. other types use the electrical charistics of a flame. The sensor is probably bad.

Check the documentation on your furnace (try the website if you can't find the paper book) for what type of device is used. Replace if necessary.

Turn off gas before attempting any work on appliances..

Answer 5

Read furnace manufacturer's instructions carefully and do it step by step. It is normally on the unit next to the burner.
If still pilot does not light you need to replace it.
It is easy to remove and buy a new one from hardware stores.
Good Luck
hmm97