Does an AAR typically fail open or closed?
 

I'm having trouble with very low idle on startups, and don't reach normal idle until the engine is warm. After that it starts and idles like it should. I'm suspecting my Aux air regulator, but think that if the heating element wasn't working, the idle would be high and not come down quickly, not the other way round. Does the AAR get stuck closed sometimes, which would cause low idle, or does it normally fail in the open position?

(Testing the heating element doesn't seem fruitful in this case because the I'm dealing with the opposite of what the heating element is supposed to do).

Take it off when it is cold and look through it.
If it is fully closed it is stuck. If you see less than a 1/4 moon opening it is open as far as it normally does.