2012 F-150 platinum. Heat and a/c went out, so I replaced the blower motor resistor, and now it’s doing this. The heat and A/C will lope (high output, then low output, then high output again, endless cycle) every other second. Any idea on what could be wrong?

 

New resistor bad?

 

Did you run the resistor before you installed it into the duct?
Did you by a reputable brand, like Motorcraft?

 

Could be the resister is bad or the pigtail harness. I’ll try replacing them later this week. Bought a duralast part, and did not run it before installing it.