Mystery Solved

Brown stuff is glue, not rust.

Generally, my 18 year-old MX5 is reliable.

There have been exceptions.

 The fuel pump died in September last year, and on that occasion the car failed to proceed.

That happened at home, so I wasn't inconvenienced very much.

I was however inconvenienced when it refused to start about a month ago, after I'd left it for half an hour with the parking lights on.

The RACQ got me going, but given that the system (when the patrolman checked it) was good in terms of generating capacity, the reason for the tired battery was a mystery.

Since then, I've taken the precaution of charging it up every now and again, when I begin to suspect it's on the way out. You can always detect a slowing down of the cranking rate.

Last week I had occasion to remove the lining covering the interior of the boot.

I found something very surprising which explained the dozy battery.

Mounted on the driver's side rear of the boot wall was an object, complete with flashing red and blue lights, with a label affixed which read - "Auto Saver Systems".

It is supposed to protect against corrosion. Apparently it works, as there is no rust anywhere on the car. The brown colouration you can see on the pic is glue, not rust.

I've decided that I might as well leave it there.

I can monitor the battery state, and use my you-beaut auto charger to keep it reliable.

Charger - all new tech is tiny.

It was good to get to the bottom of the problem.