If the RC is equipted with an "multifunction switch", this could be the culprit,they are easy to disassemble. They are printed circuits with electric grease as a lube, and over the years this dries up and messes up the functions of the sw. I have had two of them, that the blinkers would not work properly sometimes and that affects the tail lights, also. I found this out after months of trouble shooting the blinkers and tail lights. My wifes 96 Dodge van had the same problem with her wipers (part of the MF SW)
If the MF SW is the Problem, remove it from steering coloum, dissassemble it ,and clean it with "Electronic Cleaner", (not brake cleaner), regrease the contacts on the printed circuits, with a good synthetic grease, and reassemble. This process worked on my two RCs, and my wifes van.
If all else fails check the MF SW out. They are easy to fix. New ones from Mopar are (I think), $150.00
They are the same for many years.
Hope this helps
dave C. aka barracudadave67