I don't know your car, but I assume you had the engine running when checking for the lights. On my 87 420, the fuel pump is under the car near the passenger rear tire and if yours is there too, you might have heard the fuel pump.
I still would scratch the grounds and use some dielectric grease. My motorcycle trailer had very dim lights and it was a bad ground on the receptacle into which the plug went on the motorhome.
Now whether/how it affects the cruise control, I have no idea. I would look at the fuse box and see if they are on the same fuse.