Any furnace guys here? won't fire with cover on. Lol wtf

[FreePenguin]

I am going to call furnace companies tomorrow, but its worked for 4 years no issue. Used it a few months ago no issue, turned right on from thermostat/nest. Today I realized it wasn't firing up when I called for heat, I hear it like priming/but no ignite then turns off. I took the cover off the panel, vacuumed it out, looking at it. Tried it again, fires right up. Runs like a champ!

Put the cover on, thinking I fixed it somehow. It won't turn on, ok. annoying, I repeated by taking cover off, fires up. I put the cover on, nogo. I loosen 1 screw. Just a hair, where a small gap opened, and she fires up. So one little air crack in door being opened is letting furnace run properly.

I googled and found out people say its a intake clog typically, not enough fresh air? I shop vaccd the intake tube, nothing came out. I put a new filter in for heck of it, nothing. Everywhere is closed today, and its not an emergency. But tomorrow before I make a bunch of calls im trying to figure out the best route of ideas.

If the furnace runs fine, it has spark, and gas, but lacks the air. By opening the cover, it has air.

Is this a faulty pressure gauge or some kind of gauge that determines the air? kind of perplexed.

Sponsored

 

[Mikepol2]

Our furnace vents and intakes air thru white 4”’PVC pipes that come out the side of the house. One time a bird built a nest in the intake and blocked the air, it was all the way back in to the furnace. Check your intake 100% of the length all the way into the furnace.

 

[FreePenguin]

Our furnace vents and intakes air thru white 4”’PVC pipes that come out the side of the house. One time a bird built a nest in the intake and blocked the air, it was all the way back in to the furnace. Check your intake 100% of the length all the way into the furnace.

I have like wires over the intake like a blocker for animals, i wonder what I can shove through there to ensure the entire length is not blocked. It’s a weird curvy set up. But looking straight through from outside
,
Looks clean.
will double check, because appears air is the key component here.

 

[FreePenguin]

Here it is.

 

[FreePenguin]

When furnace was on, it blew exhaust out that same pipe. Does that make sense?
It blows heat out that In take

 

[Rapid Red]

if the pilot light will not stay lit, most likely the thermocouple is not working. Pilot light, heats the thermocouple. Allows the gas to the burner .very common problem. not expensive.

 

[FreePenguin]

I have an electronic pilot light. It turns on and off automatically, when the cover is cracked or off. I hear it click and turn on.

ifniter is 100 bucks, not bad. But don’t want to replace it if isn’t cause
when cover is on and fully seated, it doesn’t turn on / it isn’t igniting or whatdver
I don’t smell any gas or anything when it doesn’t

oh, a pilot light isn’t a thermo coupler. Sorry I thought they was same thing.
Could a thermocouple be affected by a cover being on or off?

 

[FreePenguin]

The pilot light stays lit and functions as it should, when cover is off or the screw loosened. Has no issue staying lit or lighting or turning off

 

[Rapid Red]

My money is on the thermocouple .... may have misstated the operation. The thermocouple is a heat operated switch, senses the pilot light is lit, allows gas to the burner.

Sorry for any confusion

 

[FreePenguin]

Does electronic ignition have one? I read they have a flame sensor instead which is a bar looking thing.

I saw the flame sensor, it’s a super hotmetal bar between a burner

reason I ask Google said electronic usually has a flame sensor and traditional pilot has a thermocouple.
I’m not a pro, just trying to get a good idea before a rip off company tells me I need a new furnace
Too many scaly companies in my area

 

[BrianH87]

Fortunately, I may be able to assist. Keep in mind it can be very difficult to remote troubleshoot issues. I do commercial / industrial HVAC for a living. Looks like you have a 90% (high efficiency furnace.) These typically do not have old school thermocouples. They use hot surface ignitors combined with flame sensing rods. They bring in combustion air through one of the PVC pipes and also exhaust it through the other one. There is usually a screen right above the burner box intake that can sometimes get clogged. (I see your pic of the outside screen. There is a second one right where the PVC connects to the furnace on the intake side.). With everything you have stated, there could be numerous things going on. Usually the integrated furnace controller will have LED's that blink fault codes and tell you what to look for. And usually they lock out after so many failed attempts at ignition. There are pressure switch safeties that can also prevent the unit from running if combustion air intake or exhaust is blocked. But, since yours tries to fire up, I assume all safeties are closed. Verify your ignitor is getting hot during the trial for ignition. You should see the glow in the burner box. You can also ohm a cold ignitor. Anything above 100 ohms is suspect, as is an open ignitor. Just don't touch any part of the actual ignitor. You will ruin it. Kind of like how you can ruin a halogen bulb if touched. It could also be as simple as a dirty flame sensor. The metal rod opposite side of the ignitor. These can be cleaned with steel wool. Gas pressure would be the last thing to check, which you probably don't have the tools for. Plus, something like that should be left for a professional.

 

[FreePenguin]

Thank you. I will be going home real soon and checking those other vent screens, I was not aware there was a two vent system going on.

I won’t be diving too deep. I just wanted to fix it if was easybefore getting charged hundreds of dollars that could of been done myself.

if it’s actual failing mechanisms, I have no issues paying for professional work.

but the fact it works when the cover is off and screw was loosen, I think it’s a clogged screen.
I will be cleaning it with shop hsv when I’m back and fire it up.
I’ve never cleaned it, I just change air filter.
It’s a 93% ruud HE, and it works amazing, I have super low bills, sounds like a jet engine taking off, and heats whole house in zero time flat.
I have 3300 in insulation too, r60 settled cellulose, and air sealed.
My gas bill is like 70 bucks in winter. (35 of that is delivery charge)

it is like 12 years old or 13, and had a blower motor before I got the house but I hope to get another 10 years out of them.

I probably should get a tune up/clean up one day.

 

[FreePenguin]

I just sucked out the entire pipe, it’s free flowing. I had shop vac in it ducking from inside and I could feel all the air being pulled in from vent. No obstruction. Yet won’t fire up.

I just started to try it lighting up. It didn’t fire up all assembled. There’s 2 green lights fully lit in the peep glass.

when it’s firing, the bottom light stays fully green, the top light flashes green, didntfire Up thouth and went to both solid green when it gave up.

What are the leds indicating?

 

[FreePenguin]

I just cracked this one screw, and tried again. Fired right up. Now there’s 3 leds, top is yellow, bottom two green. I tightened it up while running and it’s contingent running. Will see if resumes after

 

[FreePenguin]

Ignore previous messages. I have codes.

When it doesn’t start, fully closed and everything. There’s 2 lights, bottom green is solid. One above it flashes twice, pause, twice pause, twice pause.

when it ran,with cover open. It was double green and a orange or yellow above it all solid


But fully assembled as it should, it has a green light blinking twice

Sponsored