Who knows where the power to the TCU comes from? I am stuck with no power to the TCU

I am stumped at the moment. My TCU has no power to the red (with grey band) power that comes into pin 28.

I know this because I just installed a Wholesale Automatic lock up converter kit and when trying to test there is not power. Silly me didn't check pre-install that there was power but the transmission works fine so I just presumed it was there....

Looking at the documentation available on line, the power to this 'should' come from the 2nd from the bottom 15a fuse that also supplies the LH headlight. Confused, well so am I so far. So I tested the cable and there is no conductivity between the two.

If I run a 12v source from the battery direct to the pin 28 conductor to power the TCU and the lock-up kit it works. So obviously it is supposed to have power, but where does it come from? Without dismantling the dash and chasing the wire the entire length (which I may end up doing) has anyone done this already and do they know where the power splits off from the back of the fuse box circuit to the TCU?

I am about to (as long as the Mazda comes back tomorrow morning) put a long block TB42 in it so it will be off the road for a few days (or probably weeks) while I do that so I can work on this electrical issue when I get frustrated with the engine change over.

Any help, ideas or crazy theories at this stage are welcome....

Things I have done:

• Checked the fuse is OK and 15AMP
• Removed the fuse (the LH headlight goes dark)
• checked the manuals from here for electrical layout
• searched everywhere I can think of

Regards

Ok, so the Mazda is back so the engine swap (and other works) is about to start.

I will start a new thread on my work/progress in case I do something this has not been done before (unlikely), but also may be of interest to others.

Cheers

Greg