We investigate the changes of planar Hall effect bridge magnetic field sensors upon exposure to temperatures between 25° C and 90°C. From analyses of the sensor response vs. magnetic fields we extract the exchange bias field Hex, the uniaxial anisotropy field HK and the anisotropic magnetoresistance (AMR) of the exchange biased thin film at a given temperature and by comparing measurements carried out at elevated temperatures T with measurements carried out at 25° C after exposure to T, we can separate the reversible from the irreversible changes of the sensor. The results are not only relevant for sensor applications but also demonstrate the method as a useful tool for characterizing exchange-biased thin films.