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.