7.5 telltale and cigar lighter fuse blew my USB adapter

[Ontical]

I have exactly the same setup on my boat for all USB adapter cigarette lighter sockets and they all work fine.

How can it be different in the car? The adapter can’t be faulty as it’s been working with 7.5 amp fuses for a year until I put it into the car as the cigarette lighter socket was too shallow to accept an adapter.

I changed the brown positive and black negative for blue insulated crimps and put a marine 12v socket in - I located the 2nd fuse which was for the tell tales and cig lighter, which is rated at 25 amps, so I put in a 7.5 after first checking this was the correct fuse.

The adapter pinged and is now knackered.

What could possibly be going wrong? I don’t get it. The fuse is fine, the tell tales work but the USB adapter is FUBAR.

[iangsi]

The Brown in cav's is the negative you may have got them crossed.

[Robsey]

Agreed you have got the wires the wrong way round.

On Cavaliers..
Red is permanent live (+12 volts)
Black is ignition live (+12 volts).
Brown is ground / chassis / earth.
Grey with green stripe is illumination.
Grey with black stripe is illumination with dimmer control.

Usually 3rd party equipment uses -
Red for +12 volts
Black for return / ground / chassis.