new power max converter, problems

Humming noise is not the fan. I can see the fan and it does not move. Humming sound is something else. Fan is free when I turn it by hand. The only difference in the lower portion of new and old is old has one red and one white wire for + and - to connect to output side, the new PM has one blue and one white wire.

for checking polarity at batteries, are you talking about the converter supplying voltage/current to batteries to charge them. If so then no I have not.