Went on a long mostly freeway drive over the weekend. First thing I notice is the rev match won't turn on. Later on I notice the water temp gauge is pointing at zero. I didn't notice for a while since I had the performance screen up and I know the needle is almost useless. Water and oil temp read about 160 for the entire trip. When I get home and shut it down the fans ran full blast. I thought it might be a flaky fan controller so I open and closed the door and restarted. This time even the performance screen read zero degrees water temp. The temp needle does sweep at startup. Shut down again and the fans ran for at least twenty minutes. The air coming out of the hood vent was cold so I don't think it was an overheat condition. This morning the fans cranked up right at startup. 2014 M7 61K miles. It did not set a check engine light. The battery may be original but it starts up easily all the time. A few people on anther forum suggested they've seen the same problem and it was a flaky temp sensor which makes sense. One said to disconnect the battery and that would reset it but that it would eventually come back and changing the sensor was the fix. One other person suggested a bad thermostat but got butthurt when I questioned him on how that could make the dash say zero degrees.

Thoughts before I blindly change the sensor?

 

Not likely the battery. Probably the temp sensor circuit

This other guy has the same problem. See discussion in this thread:

https://www.corvetteforum.com/forums...-turn-off.html

GL

Rpn

 

Thanks for the find. I've posted on that thread as it seems we're having the same symptoms. I'll swap out the sensor tomorrow.

 

Quick follow up: I did change the sensor with a new ACD sensor. They both had the same resistance at room temp so no smoking gun there. The zero temp values didn't change after swapping the sensor and the problem persisted, so I disconnected the battery for a few minutes and even though the fans drained the battery enough to not start, the temp values came back to normal. After an overnight charge the car started right up and everything was normal. So I guess at this point I'm going with a flaky failing sensor.

 

A dying battery can do seemingly bizarre, "unrelated" things... that and corroded connectors are usually the first place to start when electronics seem involved. Just sayin' All the best.

 

This also happens if the car doesn't get up to temp in a set amount of time. The car thinks something is wrong and engages the fans to 100%. Simple battery reset will fix that. On cold days I will let the Z warm up for 5-7 min in the drive then ensure it gets past 163 coolant temps before any highway driving.