Sounds like the sending unit is sorted closed since that is the only on/off circuit.

 

How would you suggest I did this problem

 

Did you ground the lug or the threads? Threads should be grounded, and the lug should go to the relay. Lug and threads should not have continuity (~1000 ohms) at low temperature and should have continuity (~25 ohms) when hot.

 

I grounded right by where the wire that goes to the relay

 

You have to see if that's like-conductive to the lug or if it's the other side of the thermostat. You should be able to see the silicone isolator. Big threads need to be grounded, little threads (or 1/4" spade connector) go to relay.

 

There is silicone between where you connect the wire that runs to the relay and the sensor part

 

I'll try that after work today and give an update