Furnace runs for 12hrs on thermostat then goes to safety and shuts down control board indicates vacuum problem. On manual it will only run 5 hrs before it does the same thing.I have changed the vac switch but still does the same thing. cleaned the hell out of the furnace but still same problem. Check all seals on all doors no leaks any body have this problem????????
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Since you did a massive clean and lube job, hard to tell what was the fix. High pressure air can dislodge hardened ash and seems the first go to for troubles - just tough containing airborne particles!