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Please chime in if you disagree with my initial assessment:

First pass:
Connector problem.
Corrosion with spade connection and wire. 

Resolution:
Verify motor amperage requirements
Verify Proper wire size
Utilize WAGO fasteners for connections. 
Secure wires and connectors to minimize movement during travel. 
Incorporate motor fuse into system, in an accessible location. 
Utilize dielectric grease on all connection associated with the dash air system where possible.

Nice work and I will be going up under my dash to take a look at mine as well. I am glad you are checking the motor amperage, its a good idea since these are most likely brushed motors. Probably would not hurt to go ahead and pull the motors to inspect the brushes and to clean up the commutator while you have it apart. A little oil on the bearings as well will help things out and keep the amperages down.