Low current control of triac speed controller?
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Two ways of holding the gate off. One works.


  It was suggested to me that shorting A1 to G would disable the triac – it does not.


If 'A1' is the lower terminal as shown on my schematics then Figure 1 (a) should work. If it doesn't then I suggest that you have mixed up A1 and A2 or that the gate drive current is somehow strong enough to raise the voltage across the switch contact resistance enough to trigger the triac. The first option is the most likely.


  Is significant current flowing through the gate at any time?


It may be significant as far as your switch is concerned. It may also be high voltage and if your switch isn't rated for this it may not last long.



Update:

Triacs can be triggered if the dv/dt is very high. In other words, if something else up stream is switching the voltage very suddenly. I can't think what this would be in your case but we know nothing about the controller.