Passat Highline Combined Aerial & GPS ant unit

[bigchazmo]

I've got a MDF sat nav radio unit, I've recently had some issues with the ant mast which has perished.
Prior to that had great FM reception everywhere! Haven't been using radio as been waiting for replacement mast.
Tried new mast and sort of works but not great.
Discovered the combo base unit is loose but can't understand why the signal goes from poor to non-existent??
Any suggestions would be very much appreciated.
I'm trying to avoid pulling the headlining down but think i'll have too!
Also very concerned about removing side trims as mine has side airbags? Help / advice please....

[snapdragon]

Car aerials usually need to be earthed to the chassis to work properly, I suspect these especially with them having a 12v signal amplifier built in.

[bigchazmo]

would that be around the base of the aerial or at the headunit end? i'm a bit worried about pulling the headlining down to investigate as it's got side airbags etc

[snapdragon]

Yes, the signal booster is for FM and is in the base. There is a nut holding the base to the roof. A threaded tube on the base goes into a hole in the roof, and a nut is on the tube and pulls the base down tight against the roof. It is a PITA on the estate, the saloon must be awful, and in this cold weather, all the plastic clips are like glass.