A temp sensor is a very sensitive device that can get easily crushed if pressure is applied onto it. Your 2 sensors do not work now because I think they were crushed to death when they are placed between a CPU/GPU and a heatsink.
Pic 1 below shows an AMD Athlon 64x2 6000+. Do not
place the sensor on the top surface (the red arrow
). Not only will the sensor be crushed, it will also interfere with heat transfer from the CPU to the heatsink.
If you are skillful enough, you can try to place it on the side surface (eg the green ova
l) of the CPU.
Pic 2 below shows the bottom of the stock cooler of the CPU which is being used by you. As already pointed out above, the next place to tape a sensor is on the surface pointed by the green arrow
. The measurement will be most accurate when the sensor is closest to the CPU (ie the green rectangle
). However, due to the thickness of the cable of the sensor, you might have to settle by placing the sensor near the edge (ie the green oval