Whilst driving on Saturday(heavy rain), my 3 year old daughter started getting dripped on from the passengers side interior light!  The car is a 1989 E30 320ise and by the looks of it water is getting into the interior light housing and dripping into the car.  It does not appear to do this every time it rains only certain times.  I think I remember someone saying that the sunroof drain channels are the cause for this, can anybody verify this or offer the true solution.  Any advice on how you go about fixing this will be greatly appreciated.

Tucky

As you said it happened while driving the seal between the sunrof and main roof may be breaking down and allowing water to enter, so have a look at this first. It's true that as the years go by the sunroof drainage cannels can often become blocked as dirt and debris accumulates and then starts to rot out that section of the channel. (Normally the water should run straight down each side and exit underneath the car behind each rear wheel, you can see the flaps through which the water exits by removing the boot trim next to where your crank and jack sit.) 

You could check this for certain by fully opening the sunroof, which exposes the channels at the back of the sunroof. Gently insert a length of wire  into the channel and you'll soon feel if there's a blockage. If so, try to push it clear with the wire.

Next, switch the interior lights to their "off" position, remove them from their fittings (as if you were changing the bulb) and then tape the exposed wiring and bulb to the side of or above their fittings  (this will allow you to clearly see any water that may be leaking in without getting your lights soaked). Then pour a small ammount of water into the passenger side drainage channel, if no water starts dripping through gently increase the flow and you'll soon see if there is a leak. Hope this helps!