Brother of the Benz, TCCBass
You're replacing components without identifying the bad fellow.
Have you tried disconnecting things in effort to find which unit is the bad one?
Try disconnecting components down stream of the Pre-resistor to eleminate the large load.
It's amazing a fuse doesn't open.
Continue disconnecting until you have removed the load.
With everything disconnected, and the load is still present, use your volt/ohm meter, on resistance x-1 scale and test the wiring to ground. Be certain the supply wire for the P/R is disconnected.
Nothing up stream from the P/R will cause this condition.
It is easy if you do it in the right sequence.
Happy Trails Beep Beep from The Spiderman in Houston!!!