How to get to furnace flame sensor????

Emporio

I have a 82 percent efficient Armstrong gas furnace, and been having problems with it igniting. From everything I have read about it, it seems to be the flame sensor. I am trying to get to the flame sensor but it is impossible since it is crammed all the way in the back. The space is very limited, I cannot get any type of wrench to undo the screw. Please help guys with any suggestions, of how to get to the flame sensor. Here is a pic of what the unit looks like and what I am trying to part out.

Emporio

bump...I really need some advice guys...

bigMikeB

Disconnect the pilot line from the gas valve and pull out the burner assembly as a whole unit.

Emporio

I took the whole pilot unit with the flame sensor apart. I polished the flame sensor, got all the oxidized scrap off it, but the furnace still will not ignite. What else do you guys suggest? The flame sensor seems to be fine!

bigMikeB

Do you hear the spark ticking? Not igniting isn't a flame sensor issue, igniting and going off in a few seconds is the sensor. Do you smell gas when the pilot is clicking? When you had the pilot out did you blow through the tubing to see if it was clear?

HvacWiz

Looks to me like that is the igniter that goes to the honeywell smart valve, if that is the case you more than likely need to replace that valve.

Emporio

Ok, so the igniter works perfectly, yes there is clicking involved as the pilot goes on and I don't smell any gas, the flame sensor gets bright red but nothing else happens, the pilot keeps staying lid. I blew through the pilot piping with a straw , it is clean. I took the whole pilot unit off again and polished it with sand paper, put it back together and nothing. The furnace acts like its working, the fan also blows but no heat, since no gas is being burned. What do you guys recommend I should do next? I am thinking of purchasing a new flame sensor. Any further advice would be great, I been trying to keep my house warm with my two fireplaces but that is not working that great. I appreciate all the support.

hvac122

As said above this unit has a smart valve on it.
Thats the name for the gas valve. It is known for going bad and sounds like your problem. There is no good way to check one of these without a special tester. I think its time for a pro. Also if you are cleaning the flame sensor with sand paper then you have probably ruined it. It comes with a coating of some kind on it and the manufactures recommend cleaning with scotchbrite or a dollar bill only.

Emporio

Well before I start ordering parts, I want to know how hard the gas valve is to swap. Is there a DIY tutorial on this? I am thinking of changing both the gas and the smart ignitor valve. Please let me know guys if any of you have done this yourself.
I got kind of confused when you guys mentioned smart valve
the smart valve is the ignitor flame sensor assembly

And the gas valve is

bigMikeB

No the smart valve is the gas valve itself. You need to check it with a volt meter and see if it is getting 24v to the pilot valve before just changing it out. I'm a firm believer in finding something to be bad before just swaping out parts.

TobyU

Are there any blinking leds? Some will flash codes.
Are you sure the gas valve in in the on position?
Try cycling it back and forth from off to on a few times, and turn mian power off to unit then back on.

If the pilot comes on and stays.....from what you described, it sounds like the gas valve is not getting the 24 volts signal to open gas flow, or it is bad or the flame sensor signal is not telling the board that the pilot flame is there.
The flame sensor is the cheapest to try.
You can check for 24 volts at the gas valve with a meter. If the flame sensor and all is good, the signal will be sent to the gas valve to open and you will see thisi on the volt meter. If you have the voltage, but o valve opening, you almost certainly have a bad gas valve.