First, I don't own an Allegro Bus. Perhaps its the turn signal relay that has/is failed/failing? Replacing it could solve your problem. It should/may be under dash by the fuel and brake peddle. And, there may be two or more flasher relays. If so, replacing it/them with a heavy duty flasher could solve your problem.
Freightliner could tell you the model number to help in locating one at an auto parts store nearby. (1-800-FTL-HELP)
Hope that helps!
Joe and Debbie, Emma the Aussie Cattle Dog who adopted us
2012 Discovery 36J, Blue Ox and Air Force One, 2010 GMC Acadia Toad
USAF (Ret) WDØM http://wd0m.com