I just changed a dead alternator in a 99 Chevy Venture, following the Chilton manual step by step. Upon test driving it to work yesterday I noticed my temp gauge registered hot as far as it would go. I pulled into work. It sounded normal running and shut off. After work the coolant level was normal and no leaks, yet the gauge was pegged to hot with motor off. I drove it home. Nothing unusual but the gauge. I changed the coolant temp sensor. Nothing changed. Might I have compromised some wiring behind the block when I raised and lower it to change the alternator or should I look elsewhere?
Some engines have two sensors: one for the engine control computer, one for the gauge. I don’t know if yours is one of these, though. If not, I think you pinched the wire from the CTS, shorting it to ground.