1991 suzuki Sidekick- tail light troubles?

i own a shop and try looking on the left side tail light ,for a small box that clips on it,and has a wiring harness on it,this is a control unit for the rear lighting system,I'm not sure if they used it on all Suzuki,s but i think they did,and this thing will short out,and make the lights go crazy on it,Nissan used them also,and it caused a lot of problems,its not an expensive little unit ,but it can cause some real headaches in trying to trouble shoot a wiring problem,yours may not have one but if its there try getting a good used one from a junk yard and see if that doesn't fix it,good luck with it,i hope this helps.