I've recently acquired a 91 FLHTC and I'm having a problem with one of the turn signals. The right turn signal and hazard lights flash correctly but when I activate the left turn signal it just comes on steady and doesn't flash. Since the left side will flash when the hazard lights are on, I know that everything physically works, it just won't flash on the left turn signal.

My two questions are these: Does it sound like the turn signal module is bad? And: I eventually want to upgrade the rear turn signals to operate as stop/turn/tail lights. If I buy the module to make them the S/T/T, will it also fix my current problem?

 

just out of curiosity do you have a bulb out in either the front or rear of your left turn signal? or the wrong bulb in there. it takes an 1157 in the front and an 1156 in the rear, just so you know. twin element in front, single element in the rear, unless i'm missing something with the 91 model year which may be different. remove the bulb and see if it's got one or two contacts. two would mean it takes the 1157 and one contact would mean it takes the 1156.

 

Swap your bulbs side to side and see if the problem replicates itself. If it does, check you have the correct bulbs installed.

 

When I had a bad electrical connection between the stator and regulator, my battery was not completely charging. The first symptom of the battery not fully charging was the turn signals. Sometimes they wouldn't work on the right side, other times they were slow to flash or would turn off quickly. Long story short, after fixing bad electrical connection to ensure a good charge, the turn signals have worked flawlessly.

 

+1 on this post!! My '91 FLSTC would start telling me the charging system was degrading by doing bizarre things with the turn signals. If you suspect this is the case, heed the warning! Check the charging system and the battery!