I have a 2012 IC CE maxxforce DT that has a intermittent driver/defrost blower fan failure it likes to quit 3/4 way thru her route then start back up when it gets anywhere near the shop making it impossible for me to diagnosis it b/c I can not get it to fail in the shop. The one time that it failed in the bus line up in the AM I smacked the side wall where the blower is and it took off and worked for a week now she says it fails almost every morning and then eventually will start back up. Thought I had it pinned down when I found the connection at the blower was not very healthy so I corrected that and then the sickness came back. So I am starting to think it maybe a thermo switch in the motor I do know that the heat that does come from it is very warm compared to other buses. ANY HELP WOULD BE APPRECIATED
IC's are famous for melting the connect after the heater switches. Remove the switch panel and follow the harness from that heater to the next connector. There is usually and bank of them together. If I'm thinking of the correct year.
I'm betting its a connector also. I had a rear heater motor do the same. Ended up being the connector at the motor. Its a three wire connector made in a triangular shape with only one retainer. Mine looked to have separated on the side away from the retainer due to gasket force on the two halves which heated up the wire terminals and blackening the connector halves. Not a very good design for a load like a heater motor!! I pulled the terminals out of the connector, slid em back together, silver soldered and shrink tubed them.