2000 626 2.5 help needed

Check engine light was on. Mechanic told me it was a temperature sensor. He replaced it. Car ran fine for about 15 minutes. Check engine light back on. The mechanic broke the clip that holds the connector on the sensor so it came un-plugged. The mechanic says he can not fix it because there aren't any replacement clips and I'd have to buy a whole new wiring harness (even tho they broke it). So he tied it down with a zip tie. He reset the code and the car ran for about 30 minutes before the light came back on. I took a close look at the zip tied connector and the bonehead had cut the plug off and when he couldn't find a replacement he twisted the wires back together and wrapped them in electrical tape. I removed the tape (it just about fell off) and crimped on some new ends that plug together. Then I tightened the zip tie as it was loose. Now I think they have put the incorrect part in. I would normally hear the electric cooling fans come at a stop light. I have not heard them come on at all. I asked the mechanic to check it and he says the came on for him as they should (I don't trust him anymore). Now I have a leak in the overflow
tank that I did not have before. It's a small pin hole according to the mechanic. Also, while at idle coolant drips out of the overflow hose. I was not loosing coolant before the mechanic got his hands on it but he said it was.
QUESTIONS
How often should those fans come on once the car is warmed up and sitting at idle?
Can anyone tell me what the pins on this sensor should look like? The ones in there now are thin and flat. The sockets on the connector look a lot larger than the pins on the sensor. The sensor is in the top of the thermostat housing.