I have a lamp designed for 6 12v g4 bulbs. I replaced all the bulbs with LED bulbs and the lamp only flashes on when I flip the switch. I replaced one of the LED bulbs with a halogen g4 and the entire lamp now works fine. The lamp is on an ordinary switch. What is happening? I would like to be able to use LED bulbs in all 6 positions. Thanks in advance.
The transformer that steps the voltage down from 120V to 12V is probably electronic and requires a minimum load to work.
Unfortunately there isn't an easy fix for this as the electronic transformer is probably part of the fixture assembly or small enough to fit into the box the fixture attaches too, and replacing it with a magnetic transformer is just unrealistic due to the size requirements of a magnetic transformer.
Since your lamp uses 12 volt bulbs, obviously, it has something to reduce your mains voltage. Even just putting them in series would top out at 72 volts. Presumably, to save space/weight, they aren't using a transformer but some electronics which either has a minimum load current or needs a purely resistive load.
Probably, there is nothing you can do to make it operate without a halogen (incandescent) bulb.