looks like a bit map job to me. By the way, the aux fan may be bad, or have the blown fuse (maybe because the aux fan motor is corroded-personal experience). I vote (100%) for the fan switch. The best known syndrome is what you described - temp skyrockets in traffic. My suggestion is for now turn your heater on max to protect your engine. however, it may be too late. My temp is also erratic, but never goes over 100C while driving (after replacement of a radiator). I believe it may be an indication of a blown headgasket
