I just aquired a 740GL and I want to put my pioneer head unit in it. I pulled out the factory stereo, and besides the cable with all the speaker wires and 12v etc on it (loom?) and the amplifier cable, there are 4 other wires that are connected to the back - I have no idea what these are.

One is connected to the radio via a bullet plug, the other three connect to the chassis of the radio via a screw (they have a ring connecter which goes under a screw and connects to the radio chassis). One of these three has what seems to be a capacitor connected to it. They are all black and of different thicknesses.

I pulled the factory stereo out, and after a while deceided the new head unit project was going to take too long for today, so I put the volvo radio back. But I couldn't remember where these abovementioned "strange" wires went. They all seemed like earth wires, so I just screwed them to the back chassis of the stereo.

Since then the car has had quite a bit of trouble starting. The first time this happened, the car wouldn't start at all. I pulled all the wires off the back of the stereo, and like magic - the car started.

Does anyone know what these wires are for and why they're causing my car to not start?

I dont want to go and put my Pioneer stereo in and find that these wires needed to be connected...