Had similar problem awhile back. Seems that the amperage thing hold true, when there is nothing to take the load, like a working blinker, then the relay goes insane. When all bulbs are good/working, the relay works as advertised, when a bulb goes bad when turn the blinker switch to the bad bulb it blinks at an out of control rate because nothing is absorbing the load/amps. Check the blinker when you do this, if the light/bulb is good and flashing but out of control, then probably the relay or something else bad causing extra amperage in the system.
Electrical problems are so much fun!!!!!!!!!