York P2MPD08N04801B furnace won’t light

SallyVN

Hi! I’ve had problems all winter with this furnace. Replaced the inducer motor, pressure switch, high limit switch, and flame sensor. After replacing the inducer motor and pressure switch, it has worked well for about a month and a half. Prior to that, I was getting lock out errors frequently until it finally just stopped lighting at all. I thought it was all good until last night when it stopped lighting and gave me the 7 red flashes again (ignition lock out.) It tries to light, but I am not getting a flame at all. The ignitor glows as it should, but none of the burners light. After three tries without lighting, the fan comes on and blows cold air. The burners are mounted horizontally with the ignitor in the path of the first burner. The flame sensor is in the path of the last burner.

The filter is clean...replaced 3 weeks ago.
It’s not quite warm enough here yet to go without heat, and I am out of work due to covid19, so funds are slim.

I did have the gas company out to check the gas pressure...they said it was good. I’m sorry I don’t remember what he said it was reading, but he did say more than enough pressure.

Furnace is in the basement, it’s natural gas, and fairly old (probably early 80s.) Any advice on what to look for...my son can help with replacing parts if necessary. I’m no hvac tech, but I’m intelligent and willing to listen. Thanks in advance.

JUGHNE

Is this the first season with problems?
Have you been in house several years?

How about pictures showing the entire furnace including the exhaust system. Also a couple with the doors off showing internal components.

In what state are you located?

EdTheHeaterMan

@SallyVN After many years with little or no maintenance, (no fault of yours, if you were never told to do so) the burners can get clogged with dust, rust, and corrosion. In this illustration, there is a burner similar to the one in your furnace. The end of the burner closest to the flame has a small slot that aligns up with the ignitor. Gas from the burner flows out the larger openings to create the main heat.

The smaller slots line up with the ignitor and that is the gas that starts the burning process. If the small slot is blocked, then the gas may not get close enough to the ignitor to start the flame. Cleaning the slot(s) will solve the problem. These slots also allow the flame to "run" to the next burner, then the next until the last burner is lit. That is why the flame sensor is at the opposite end from the ignitor.

I recommend a professional for this, however, with your current economic situation you may be able to clean this slot enough to get past the last few weeks of the heating season. If you take a coat hanger and bend a small hook at the end. Use that to see if you can scrape the slot enough to loosen the blockage. Then take the crevis tool from a vacuum cleaner to remove any debris.
BE CAREFUL NEAR THE IGNITOR IT IS VERY DELICATE. Do not touch the hot surface ignitor because they are very brittle.

HVACNUT

Do you have an electrical meter? Is there 24v at the gas valve?

unclejohn

Sounds like the only thing they didn't stab at was the gas valve.

drewlinden

I am having the same problem for several seasons. Igniter glows, but the burners don’t light and after three tries the furnace locks out. I’ve been through all the same changes.

Did you ever determine the problem and get the furnace working again?

thanks

digitalman218

I would try (if you're handy with your hands) what ed said about cleaning the burners. I am just an old truck driver and I had the same problem you're facing now, and after researching on u t u b e I cleaned my burners and got the stove to stay on. It would come on, then go off, then come on and go off. This is called short cycling and I had a hunch that's what it was doing. So after watching a few videos, I got a little mirror and positioned it where I could see the end of the burners, then took a wire brush and a piece of sandpaper and carefully cleaned the ends of the burner. And he is 100% correct, be VERY careful around the igniter as it's more fragile than a piece of lint taken out of the dryer. Mine was easy cause it just screwed in from the top,so I just took mine out before cleaning the burners. I really didn't have any money to buy any parts, so after trying this and it worked, me and the cats were glad to get some heat back into this cold house here in KS!! If you're not comfortable with doing this yourself, you can pay somebody to do it, if you have the $$. But, if you have a plan with your gas or electric company, your furnace repair may be included! Good Luck