I cannot get my turn signals working. I have two flasher units(one new) and neither works. I attempted to test the flasher unit by removing it from the three prong plug and attaching a hot lead to the input side and a test light to the output side. The test light, 'lights up', but does not flash. Is this a valid test, or is the test light to small of a resistive load to cause the thermal flashing unit to cycle on and off?