1997 Chrysler Grand Voyager cooling fans

Hi I have just had head gaskets done on my voyager 3.3 1997 everything was fine but the fans will not cut in automatic like they should as when I brought car it was hot wired so the fans run permantley when running if I unplug this quick fix! The engine boils up after a while and the temp gauge says o.K middle of gauge because they r not cutting in like they should do u think the ecu is to blame for this as fans won't cut in automatic, and the person who owned it previous hot wired them for this reason i've checked ev ery thing else and this is my only lasdt thought can u help