I personally never cared for speed fan because I have gotten wrong temps and never was able to control fans. With a temp like that the GPU would be about to catch fire if not already on fire. Besides if it was that high the card would of crashed. Usually the max temps are 110°C then they crash from over heating.
That temp reading is wrong try CPUID (HardWare) HW monitor, GPU-Z or even OCCT to get the temp that is reliable.