You can pull the connector off, insert a jumper wire into it and ground it. The fan should come on. If it doesn't, the problem is in the circuit. If it does, replace the fan switch. I suggest that you purchase Rodney Dickman's 225 ON, 210 OFF fan switch to reduce the probability of overheating. The switch kicks the fan on before it begins to overheat. If you run a 195 thermostat, the engine will operate in it's correct temperature range. That switch resolved the overheating problems in both my cars.