Another thing to keep in mind is that your TC lock signal may not be a simple steady voltage applied, it may be a PWM signal (as in my 2002 GMC). It's important to find that out before just sending power to the TC lock wire.
Keep in mind the TC lock up clutch is relatively small compared to a manual shift car clutch and the auto trans is designed to unlock the clutch anytime the torque demand from the driver is likely to exceed the limits of the clutch.
This is to give a longer life to the clutch unit.
That depends on a lot of stuff(car make for example).
The Aisin transmission in the Tracker is an A44DE (VERY closely related to the A43DE used in the 84-86 Cressidas and Supras) and the A43DE in the Toyotas (along with the A340E in my 88 Cressida) would lock under WOT operation. First gear was TC lock-free as the Tracker is but in second gear at WOT ~4400(peak torque) you could hear and see the engine speed fall a few hundred rpm as the converter locked.
In the Tracker, the same transmission make but a different brand and slightly different model, the TC won't lock under heavy load no matter what the gear. I was under the impression though that this is done because it revs the engine up a little higher without completely changing out of gear.