I had the E04 error on my Minimax NT model 400 DV and the inside indicator light flashing 3 times to indicate lockout with fan failure. However, it was not the fan.
1. removed hose from fan in top of unit.. used paper clip to make sure no debris was in the nipple on the fan housing.. (it was all clear)
2. removed other end of hose and blew air through the hose to make sure no debris was within the hose.. (it was clear too)
3. checked ohms on pressure switch with and without vacuum to make sure switch was working correctly.. (it was functioning correctly)
4. reinstalled switch and checked voltage during ignition cycle and verified 24 VAC when fan ran and switch closed.. (ok so fan, switch and voltage all good)
5. check voltage on ignitor.. should be 120 VAC but nothing there..
6. removed ignitor, closed circuit and 120 VAC was there.. so problem appears to be ignitor (nothing about the fan was an issue.. and just a waste of time troubleshooting it all!)
7. order ignitor.. will see what happens when replacement arrives