In that case, see if you can find the layout of the thing to get near where you need to be and inspect the PC board fro bad connectuions. The wway the heat flowsa in these things can do nasty things to solder joints.

And the fact that it is not goiung into protection means it may well be just bad connections. When things short out, it usually won't kick the relay in or maybe blows fuses. I rarely say this - but it might be something simple.