The original style flasher uses a bi-metal contact. The current passing through the contact causes the metal arm to bend from the temperature change and break the contact. The arm then cools quickly, bending the arm back to re-make contact for a second and cycle again. These units are very sensitive to the amount of current going through them. If you switch to LED lights, the current is reduced and the arm never heats enough to break the contact. Likewise, too much current (say from pulling a trailer with more lights), and the flasher flickers rapidly.
The original style flasher uses a bi-metal contact. The current passing through the contact causes the metal arm to bend from the temperature change and break the contact. The arm then cools quickly, bending the arm back to re-make contact for a second and cycle again. These units are very sensitive to the amount of current going through them. If you switch to LED lights, the current is reduced and the arm never heats enough to break the contact. Likewise, too much current (say from pulling a trailer with more lights), and the flasher flickers rapidly.
Back to your issue...it sounds like either one of your lights is not lighting to keep the unit flashing (burned out bulb), or the flasher is rated too high for the number of lights the TR3 has operating. They do make electronic flasher units that compensate over a wide range of currents. Almost all of the older, say pre-1980's, units are interchangeable as far as the electrics go.
Back to your issue...it sounds like either one of your lights is not lighting to keep the unit flashing (burned out bulb), or the flasher is rated too high for the number of lights the TR3 has operating. They do make electronic flasher units that compensate over a wide range of currents. Almost all of the older, say pre-1980's, units are interchangeable as far as the electrics go.