Jamie wrote:

I have an idea for you.
get your self a low voltage auto tail light lamp.
use it in place of the fuse that blows. start disconnecting
things until the lamp glows dim or not at all.
this will allow you to keep the circuit on, you can then
track down some heat traces which won't be much..
actually, you'll be able to do a volt tracking using that
method..
You might have some logic issues that is causing current
to exist only when the circuit is fired up.

Good Lord. You made a suggestion that's slightly sensible !

Lightbulbs do make practical current limiters when selected appropriately.

In this case an auto 12V lightbulb will be no good however, the volts involved
won't even barely make it warm. I'd initially suggest a 1.5V or 3V type. Then it
may serve some purpose.

Graham