Hi,

I have a Rheem Classic 90 plus. The status indicator LED blinks twice followed by a pause. The manual says it indicates "Pressure switch is open." It doesn't say which pressure switch is open "blocked drain pressure switch" or "main pressure switch".

I checked the two small tubes leading out from both the pressure switch. They are all clear.

Also, I noticed that if I do not tighten the screws on the top panel, the furnace works. Is it OK to leave it like that while I try to diagnose the furnace.

Any help is appreciated very much in making this furnace work.

Thank you.

Also, I noticed that if I do not tighten the screws on the top panel

Explain exact location of screws and Exact model number of furnace.

It looks like this:
http://www.rheemac.com/products/Prod...ificModel=RGRA

By panel, I meant the top door that provides access to the inside of the furnace.

Thanks.

Something could be blocking the incoming air. Check the pipes that go outside for blockages.

The incoming air pipe is coming from the wall, but doesn't show up outside (the exhaust pipe does open outside). Could the incoming air pipe be opening in the crawl space?

While we are trying to figure out this issue, is it OK to keep the furnace running by leaving the top door of the furnace a crack open?

Thank you very much!

is it OK to keep the furnace running by leaving the top door of the furnace a crack open?

It is never OK to operate a furnace by improper means! Now if you are freeezing to death that could change your position as to weather to run it or not. As a professional I would be a fool to give you any other advise.

Where is this furnace located?

What is the exact model number?

If the white combustion air intake pipe is clamped to the unit and the furnace is located in a open area you could disconnect the pipe and allow it to drawn in the surrounding air. If the furnace runs correctly after doing this then you know for sure the intake pipe is plugged up somewhere. NOTE do not disconnect the discharge pipe and allow the fumes into the home. Only the intake combustion air pipe should be disconnected for the test.

That did it! I pulled the intake pipe and saw bright light coming in from the wall. So the pipe did lead outside. I went outside and discovered why I couldn't find it earlier. The intake was completely covered with leaves. And that explained why the pressure switch open error was showing, because it wasn't able to get air from outside. Everything looks good. We are warm and toasty now.

By the way, I don't know where to look for model number. On the top of the unit it just says Rheem Classic 90 plus. Inside the two door panels, there are circuit diagrams, etc. but no model number.

Thanks very very much for your expert help in solving this problem.

Warmly,

Mich

Glad you got it going. BTW that pipe should be installed so as not to be blocked.