This paper presents experimental results obtained with a monolithic implementation of a 3-axis thermal convective accelerometer. In particular, impact of packaging on sensor sensitivity and bandwidth is studied and sensor resolution measurements are performed. Compared to previous work, the originality of the proposed architecture is the absence of complex 3D assembly for out-of-plane sensing. Then, a single suspended planar structure, obtained by front side bulk micromachining of a CMOS die, is used and a front-end electronics is co-integrated on the same die. For in-plane accelerations, a classical differential thermal measurement is implemented with two pairs of detectors symmetrically placed on both sides of a micro-heater. For out-of-plane accelerations, a simple common mode temperature measurement of the same detectors is proposed for the first time and only one micro-heater is required for the measurement of acceleration in three orthogonal directions.