I've been chasing a radio interference problem for six months. It got to the point where even a 50,000 watt station only 70 miles away was getting hard to hear for static.
Nothing worked. I cleaned the antenna lead ends and used dielectric grease, ran a different ground to the radio, checked the spark plug wires, and was a my wit'* end (admittedly, not a long trip)
It'* August in Northern California, with the typical triple-digit temps. And, my blower fan has slowed down considerably over the last 3-4 months. It started out OK but slowly lost RPM as I drove the car. It was sweltering in the cabin.
I checked out the resistor and the condenser for debris, and both were OK, so, I bopped over to the parts puppies last week and got a new blower motor and fan, and installed it, after wrestling for an hour or so with the bracket that holds the fuel lines.
So, the A/C is again effective, and there was a bonus-the radio problems went away! All I can figure is that the dying blower fan motor was putting out radio interference in the AM/FM band.
Is that a weird one, or what?