Rheem Classic 90 Plus furnace - Pilot light acting up

derekahc

Hello!

I have a Rheem Classic 90 Plus in my condo, circa 1998. I moved in about a year ago, and have had no problems with the furnace until now. I was hoping I could get some insight on the issue I'm having.

It's been cold here (20-30 degrees). Yesterday, I noticed that the heating in the condo wasn't working, and the temperature had dropped to about 60, compared to the 71 degrees at which it had been set. I fiddle with the thermostat some, and no dice. The fan seems to be working fine. If I set the thermostat to "Off" (as in neither Heat or Cool), and set the fan to "On", the fan turns on just fine. But when set to Heat, the fan turns off. When it's trying to turn the heat on, I can hear the furnace start making noise, and it vibrates, but the pilot light never turns on.

I took off the upper access panel on the furnace, but I'm not well-versed enough to identify if there is a problem by sight. However, with the access panel off, I used the thermostat to ensure that it would try to start heating. This time, the pilot light ignites and the fan starts, properly beginning to heat the condo. I replaced the access panel, and after a couple minutes, noticed that the heat had stopped again. I repeated the process, and it began working. At this point, I can consistently get the heat started by removing the access panel, making the heat turn on, then replacing the access panel without fully screwing it in. However, after a while of the heat working consistently for a few hours, it will eventually stop igniting the pilot light again, and I have to repeat the process.

Does this mean that there is some kind of air flow problem preventing the pilot light from igniting? Again, I'm not very knowledgeable about furnaces, so I don't know if there are any risks involved with keeping the access door not fully secured.

Additionally, while the pilot light is on, I can see some infrequent orange flickers in the flame, rather than pure blue all the time. This has me worried that there may be a gas leak, although I can't smell anything and do not feel ill. I have a carbon monoxide detector in the condo, and it has not gone off.

Any help will be greatly appreciated. It's cold, so I'm eager to get the heat back on, but not at the cost of a gas leak!

Thanks!

Derek

JUGHNE

Check your outside air inlet. It should be near the exhaust pipe or part of an assembly outside.
It may be partially plugged with frost or snow.

derekahc

Hm good idea! I do not have access to the building roof, where I imagine the air inlet is. I've contacted the HOA about it. In the meantime, do you think there's any danger in leaving the access panel a little ajar?

Thank you!

Derek

JUGHNE

First post a picture of the front of your furnace with the top door removed. One front on and 2 others at about 45 angles.
Include the PVC piping for the furnace.

derekahc

derekahc

Let me know if the pics aren't quite useful! Thanks!

Abracadabra

Verify that air pressure switches are not kicking off the burner.
Verify proper pressure across combustion chamber
Verify proper draft inducer operation

JUGHNE

This has the symptoms of your combustion air inlet being plugged. You can see that the air inlet pipe just dumps air into the burner area. Pressure switches shut down the burner if the inducer fan has no air to suck thru the burners.

Often these are vented out the side wall of the basement, something to look for.

If the outside temp gets above freezing with sunshine the frost on the inlet may melt.

Reasons to not leave the top door off during operation for any extended length of time include:
----The air in the furnace room may be contaminated by cleaning products etc.
----There may not be enough free air available for the furnace to use for combustion as what used to come in thru the inlet pipe now is pulled out of the house by the small inducer fan. This air could come down some other chimney for water heater, fireplace etc.
----Also running clothes dryer, kitchen & bath exhaust fans could pull your furnace gases out of the burner compartment.

So if you are to do this, I recommend cracking a window to allow more fresh air into the basement/furnace area.

You need to get this resolved ASAP.

neilc

1st picture,
is that gas line service valve open all the way?
looks a little blurry but also looks 1/2 closed as I'm seeing it

neilc

nevermind,
it's the paper tag I'm seeing

derekahc

Hey all,

It appears to be working now. As I continued to mess with the furnace, the ignitor began not working.

I believe the initial problem could have been nothing more than a dirty air filter, combined with ice on the air inlet as mentioned above. The problem with the ignitor appears to have been caused by the pressure switch. I took it off, cleaned the tube and the orifices at both ends, and it all began working again.

Thanks for all the help!