cooling fans not turning on.....

hi peeps wanna know if anyone can help or has an idea i have a 2000 imp 3.8 i had a leak in my radiator took to my uncles radiator shop and had it fixed when i put radiator back in i was puting coolant level sensor back on radiator and when i looked at the sensor probe on the sensor it was rusted when i touched it it fell off so i put sensor back on radiator and now cooling fans do not turn on anyone had this happen please help.....