Turn signals dont work

My older peterbilt trucks 94-99 have them behind the dash

 

i have a 93 fld120 and had a turn signal/flasher issue...(http://www.thetruckersreport.com/truckingindustryforum/trucks-eighteen-wheelers/79003-intermittent-turn-signals.html)...

installed a new switch/lever on the steering column, didnt solve. ended up using the solution offered up in the thread i posted about it (see link). all worked fine until i rewired my brake/tail/turn lights (which corrected a short that i didnt know was there). the rewiring caused the turn signals to act up again. i ended up figuring out that undoing the "flasher work around" and putting in the original flasher fixed the problem.

 

Could also be a mechanical flasher with all led lights, not enough resistance to make it flash.