"Pulsing" auxiliary power

[davekmoore]

Some odd stuff had been happening with various electrical items recently. Got some compressed air and switch cleaner into the fuse box (although simply ensuring the fuses were properly pushed in might have done the trick on its own) and all good except for one item - the aux power supply which goes from somewhere under the dash, through the correct rubber channel to the door, then up to the quarter light to power my GPS/phone cradle. This continues to have power for a few seconds, then goes off again, then power back on etc. This is particularly annoying as the phone beeps and iTunes cuts out on each cycle. It seems to be about 2-3 seconds per cycle and doesn't vary whether the motor is running or not, or with changes in road speed, or with changes in road surface, all of which suggest to this non-electrical person that a short is not the cause.

The cable was installed by an audio specialist (although recent searches for rattles in doors show the rest of his work wasn't very special), so I don't know where he would have taken the supply from.

Thoughts appreciated please.

[Cus]

Hopefully he took the power from the lighter socket (already fused & switched), follow the lead and see where it comes from though, you can pick any wire at random in the dash and have a 50% chance of getting 12v out of it. (Generalisation)

Also check where the ground goes, you can pick up earth off any metal part (also a generalisation) but if they've not cleaned the paint off and just tapped a screw in, it may not be a clean connection