Quick Fix Mr. Heater Big Maxx [Won't Ignite]

If your Mr Heater Big Maxx garage/shop heater won't run and has a 3 flashes / blinks LED error code, here's how to fix it.

Although you might be tempted to just replace the pressure switch, that most likely isn't the problem. You'll need to open the side access panel and inspect the clear tube that goes from the inducer motor to the pressure switch. It could be blocked. Also, the exhaust (chimney) could be blocked.
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