Make sure the connection to the dimmer switch is good especially as it pertains to the R/Y wire. Also, take the voltage reading of the R/Y wire w/the low beams on and pull back the lever of the dimmer switch to turn the high beams on and see if the voltage goes from 12 volts or so and changes to a low voltage for a consistent amount of time. If it does not, then the problem is the latching mechanism of the dimmer switch.