switch for fan and radiator check engine light keeps coming on ?

Hi, unfortunately, I'd need more information to create an opinion on this. What diagnostic trouble code or codes are appearing? Can you share them? What testing has been performed to determine it's a "switch"? There is nothing to determine or share without knowing more data. I can't possibly dream of what's wrong unless I know what's happening based off of data retrieved and testing performed. If testing has not been performed, it needs to be performed hands-on with the vehicle. No measure of me imagining and guessing what your concern might be and how to fix it or possibly help you legitimately. Seek local guidance - or post test results and codes retrieved so I can evaluate.