part of the heating and or air conditioning unit 16 the support 74 essentially comprises a block of parallelepipedic shape having two opposite walls that respectively delimit two u shaped receptacles 80 and 82 these two receptacles being aligned along an axis xx the receptacle 80 having larger dimensions than receptacle 82 provided between the walls 76 and 78 are two opposite deformable lugs 84 and 86 ending respectively in two hooks 88 and 90 that are turned towards one another the support 74 allows a radial attachment of the clip 52 in the direction of arrow f 2 during the introduction the hooks 88 and 90 move apart from one another and then move closer to one another again once the clip 52 is immobilised in the support 74 reference is now made to fig1 which is a perspective view corresponding to fig6 the clip 42 which has a circular cylindrical shape is able to be received in the support 74 of fig9 and 10 which is also represented in perspective in fig1 the clip 42 may also be received in a support 92 such as that represented in fig1 which comprises two pairs of elastic lugs 94 spaced axially from one another.