My sons car started overheating so i noticed the waterpump leaking which I replaced. Now the radiator fan isnt coming on. I also changed the t-stat. Here is the part I cant figure out. When I test the new temp switch at T-stat housing and I have my test light grounded and probe the green wire the test light comes on and so does the fan? I am not sure whats next. Any help would greatly appreciated.

 

The switch is a switch to ground, the load from at test light can be enough to pull the relay in. Unplug the switch and put a jumper wire in the plug, the fan should come on whenever the key is on. This proves the fuse, relay, and fan motor are all OK. Then the switch must be bad.

You can also put a jumper wire in the switch plug so the fan runs all the time; test drive like that and if it still overheats there is another problem.