keep going through temp sensors

[leanburn]

i rigged up my own relay for my fan useing a 180 degree sensor in the intake that completes the ground circut. i have fried 2 sensors now and don't understand how thats possible. when i disconnect the wire that goes to the sensor and hook it straight to ground the fan works awsome but for some reason when i hook to the sensor it works for twenty minutes and thats it, time for a new sensor. what am i overlooking?

[Chryco Psycho]

use a relay , the load to ground probably eceeds the sensors capacity , trip a relay using the sensor ground then switch the load to ground through the relay

[dodj]

 
I think you have the fan load current going through the sensor. The fan relay should be connected to a temperature switch, not a sensor. A sensor is a variable resistance. 

[leanburn]

sorry i shouldn't have said sensor. it is just a temp switch.

[dodj]

What are the contacts of the switch rated for? (amps)

[leanburn]

Not sure. I assumed that these were designed for what I'm useing them for but I guess not. I should have known that it was to easy