1991 Dodge Caravan overheats and no back running lights.

I have a 91 dodge caravan, 140k miles, not sure on engine size. Recently my van overheated. We found that the radiator fan was not working. Our mechanic friend said to check the back license plates lights and that could be the problem. We checked, they were out and we replaced them, which did not fix the radiator fan. Then we found out I have no rear running lights when u turn the lights on. We have turn signals, and brake lights but no running lights. This is really confusing my husband and I. Could someone please tell me what could be wrong? Thank you.