Corsa Fuse keeps blowing

[udder]

My Cig lights (a 20amp) fuse keeps blowing.

I recently bought a 20amp fuse to replace the one that went. It blew the cig lighhter and my reversing lights.

I was told by the motor shop guy that leaving your sat nav plugged into the lighter when you start can cause a short pulse and blow the fuse.

So I took the Sat Nav out and then plugged it in after starting. Fine at first.

Got into the car today to find it's blowne again, not even used the Sat Nav.

Anybody know what it keeps blowing?

[woodchopper]

Have come across a faulty reverse lamp switch on the gearbox which shorts out when the car is put in reverse - or else try disconnecting the cigarette lighter for a while therfore eliminating it from the possible cause.