When you want to measure current AT ANY TIME AT ALL, here is what you do:
Cut the wire or the track with a knife and insert the multimeter using the highest range on the meter. This can be the 10amp range.
The highest range is the best. If the needle only moves a small, small, amount, you can change the range. It is very difficult to measure current around a 3-terminal regulator as any impedance you introduce via the multimeter leads will upset the operation of the regulator ENORMOUSLY.
Feel the regulator. If it is getting hot, current is flowing.