How to know if you have a tracking device on my car?

A GPS tracking device usually contains a GPS receiver and a cell-phone + sim card in order to send data to a remote location from the car, it would help to know if you think the device was 'placed' or installed in your car, a placed tracker would have to use it's internal battery which won't last very long, if the tracker was installed (which obviously takes longer), it would probably be taking power from the car's battery and therefore can operate indefinitely.

Ideally the GPS needs to be able to 'see' the sky in order to determine it's location, so unless it has an external aerial, I wouldn't expect to find it anywhere on the car where it has large amounts of metal above it, i.e. under the car (away from edges) or car bonnet etc.

Detecting the tracker would be a the same as detecting a cell-phone, there are devices you can purchase to do this but they're not cheap, which really just leaves physically looking for the device, it could be as little as 40mm x 40mm and if it has been 'installed' will have wires connecting it to the car's power supply

 

Yes, Favourite areas of the car are, in the dashboard or maybe the light fitting in the roof lining, it will need an always-on power source not effected by the ignition switch e.g. internal light or possibly the cigarette lighter (on some cars)

Other Notes:-
1) When not being used the car is less likely to be detected if it is in a garage because the GPS needs to see the sky
2) The cell-phone in the tracker can either automatically transmit it's location at regular intervals or it can be 'called' and asked 'where are you now', the second option uses less power, whereas the first may only last a few day on internal batteries

 

If you are going to wire in the tracker, it is best always-on, it would work from a car battery for many months before draining it, also it takes time to work out where it is, so on a short trip it may not have time to get a satellite 'fix', they sometimes have movenent detectors so they can 'sleep' when in the same place

 

If the tracker has been off for some days, is mounted in the car with little or no clear view of the sky and is trying to get a satellite fix in an urban canyon, I wouldn't be surprised that it could make a 10 minute trip without finding it's position