Differences between temperature maps built using data from detector 143-1a, for Surveys 1 and 3 (top) and 2 and 4 (bottom). In both cases, large-scale features appear. Their amplitude and disposition on the sky are compatible with residuals from the solar dipole, due to time variations of the detector gain, of the order of 1 to 2%. These residuals should be compared to the amplitudes of the solar dipole, 3.353 mK_CMB, and to the orbital dipole that is about 10 times lower.