The signal flasher works by heat buildup from the current draw of the bulbs. When it attempts to flash more than just the vehicle bulbs, heat buildup is very quick. This results in the trailer and tow vehicle signals flashing very quickly compared to the vehicle by itself. A heavy duty flasher is exactly that. It is made to require a higher heat buildup to operate the current breaker inside. The combination of both vehicle and trailer lights will flash at the same speed with a heavy duty flasher. As gmachine said, you may need the convertor for the trailer signals to operate properly, it is usually included with a tow package.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"