Last night I plugged in my block heater for the first time to see if it worked. I know how block heaters usually work and don't think that there would be any connection to my problem but who knows? My temperature gauge is completely dead starting today, the needle is pegged against the cold side. I hooked up my Dash Command program and confirmed that my operating temperature is normal so that would suggest that the temperature sensor and associated wiring to the computer is functioning. Any thoughts?

2008 4.2 s-type.

 

Look for broken or disconnected wiring at the connectors. Check wiring loom for breaks.