Bizarre reading from a single DS18B20

I'm new to the Arduino and 1-wire sensors, but I had the sensor working perfectly with my Uno. I then built a dedicated shield with connectors and resistor for the 1-wire and now can't get it to work. When the shield is not connected, ie no resistor or 5V connection, I get a reading of 32 Fahrenheit (or 0 centigrade when I change the code to display centigrade). When the shield is installed but no sensor is connected, I get -196.60 (or -127 centigrade). When I connect the sensor, I get the same readings. How do I know if the sensor is damaged and not working?? As I said, it was working and was intermittently not working - now not at all. I'm using it in parasitic mode.

Thanks for your help!!

You could first try it in normal mode; -127 means the sensor is not found. The cause can be in the sensor itself, the wiring (connection , capacity, pull up resistor etc) or in your sketch. Did you modify it recently? Post your code if you want us have a look.

This http://milesburton.com/index.php/Dallas_Temperature_Control_Library contains a device count function. might be helpful

The sensor was - it thanks! Although each wire checked out, when I desoldered and then resoldered the sensor, it worked.

Thanks for your help!

Doug