The_7

i am currently troubleshooting an overheating problem with my 7. first of im trying to test the sensor and guage to see if its actually overheating or if the electrical stuff is messed up. a new water temp sensor is $30 and i am very low on cash so i dont want to buy it if its not broken so i need some help testing it. what is the proper testing procedure? i measured the resistance with one lead of an ohm meter inside the sensor and one touching the end (i removed it) im not sure if this is the right way (correct me if im wrong). the haynes manual says when the engine is cold the resistance should be between 150 and 233 ohms. however i could get readings from .5, fluctuating around 10-15, and sometimes 20 megaohms by moving the inside lead around. am i doing something wrong or is my sensor bad? thanks in advance for any help.