Suggestions for Rheem 90+ furnace

[greedyman]

Went on a service call today to replace a circuit board that had a bad blower relay in it. Got the new board installed, ran some test runs and furnace was operating normally. When i put the top cabinet cover back on the burners went out and a pressure switch error showed on the diagnostic led. I remove the cover, reset the furnace, and it ran normally again. Until I put the cover back on. I checked the intake pipe for blockage and it was clear. Checked the drain hoses and trap and they were clear also. I don't know how long this has been an issue with the furnace. I ended up leaving one side of the cover a little loose to allow more air intake into the cabinet and it ran normally after that. Is it a bad pressure switch, plugged secondary, or could it be something in the new circuit board? Any suggestions?

[XcelTech]

make sure the door pressure switch hasn't been replaced with a normally closed switched or see if they rigged it to work backwards.

[ch4man]

did you measure what the pressure switch was reading with your manometer?

what was the switch rated?, also since these furnaces seal so tight the pressure switch refernces different ambient pressure whether the cover is on or off.

need to take that in to account when setting up your manometer

get your post count up, if your not sure what i mean we can talk in the locked areas

[greedyman]

I dont have a digital manometer. Am interested in hearing about how to set it up when I do get one.

[carene 7]

Inclined manometer has more potential in my opinion.Have three and a magnahelic as well.Pretty neat what they can tell you.