The heater wouldn't run, the blower would come on but no heat because the burners wouldn't come on. A technician got it to run again until it came up to temperature, then it stopped. Then we replaced the pressure switch, the ignitor and the transformer and we got the burners to come on and it ran for about 12 hours. It wouldn't come on again and we were getting three blinking lights from the ignition control panel still, which the manual says that the blower vent is blocked. Once we checked the old transformer after we had the new one installed, we were getting 24 volts. Then we replaced the ignition control panel and put the old transformer back on because it had spades in it that we could use. The heater isn't running and we're still getting three blinking lights from it. We checked the voltage of the transformer and we were getting the correct 24 volts to the pressure switch. We didn't replace the limit switch that plugs into the pressure switch. Is it possible that the limit switch that's connected to the pressure switch is open and not closed?

Have you checked to make sure the flue vent is clear, the obstruction could be in vent pipes or even inside the inducer motor housing, many times if all else fails you have to remove inducer motor and housing and give it a good shaking, might be surprised what might fall out

OK,thank you and we'll try removing the inducer motor and housing and as you suggest. I appreciate the quick reply and suggestion.

have you checked to make sure the flue vent is clear,,the obstruction could be in vent pipes or even inside the inducer motor housing,,many times if all else fails you have to remove inducer motor and housing and give it a good shaking,,might be surprised what might fall out

How do you clear a flue vent? Where is the inducer motor & housing?