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utphotoman
Rheem 90 Plus furnace problem

I just reinstalled a Rheem 90 Plus furnace I had in a previous home. I knew at the time I pulled it out of the old place that I had to replace the control board, so I did that and completed the reinstall.

Now, when the door safety switch is pushed to check if it runs, both blowers kick in, the igniter never kicks in and this is all without the thermostat even being hooked up. Also, I get three blinks on the light. I think that's suposed to be something to do with the limit switch being out, but I can't figure out why everything runs without the thermostat being connected.

I'd appreciate any help. It was -29F here the last two nights.

Thanks.

Sten
Re: Rheem 90 Plus furnace problem

It should say what the error codes are on the front access panel, but it sounds like the limit to me. If you can follow the wiring diagram it will tell you where the limit is, take it out. Get a cheap multi meter and set it for ohms, then go across both leads, if you have continuity numbers will show or the meter will beep. This means it's good, If you get nothing you have a bad limit. You have to take it out to get a true reading. Be sure that the board you got is good.
When a furnace goes off on high limit the stat opens but the blowers continue to run in order to cool the heat exchanger, it's the same as the stat not being wired in. Good Luck!!! :)

utphotoman
Re: Rheem 90 Plus furnace problem

Thanks, Sten.

I did as you suggested and found that one of the two roll-over switches had gone out. I was excited, thinking that I'd finally have a warm bedroom tonight . . . not the case.

After changing out the roll-over switch, it continues to trip, usually in the middle of a cycle after running one successful cycle. I can't figure out why.

The furnace exhaust is 4 inch pipe and is unobstructed and I've watched the flame during the first cycle and it doesn't differ from the flame on the second cycle when it trips.

I have noticed that no condensation drains from the furnace until the end of a cycle. Could this be part of the problem or is it normal?

What would you suggest I look at next?

Thanks.

canuk
Re: Rheem 90 Plus furnace problem

Time to call in a pro.

Sten
Re: Rheem 90 Plus furnace problem

We had a call once on a Goodman 90+, the installer put the Condensate drain hose on an upper connection instead of lower at the Inducer motor so it would run for a while and fill, it couldn't drain and shut down. Sounds similar but if it was running before and you didn't change anything that might not be it, check anyway. It doesn't take much to block those intakes or exhausts, spiderwebs will do it. Good Luck!!! :)

If your roll out was tripped you should get a Tech down there to check your Heat Exchanger. Since you have a 90+ it wouldn't have been a downdraft that caused it to trip

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