I just bought my first boat and it came with 2 HDS 12 Touch units. One on the TM and one at the console. Both graphs/transducers are acting weird in regards to water temp. Neither unit was set to display water temp when I bought it so either the previous owner turned it off because he knew it was wrong, or he just didn’t care about water temp. Either way, I’d like help in figuring it out. I know it may just come down to buying new cables or transducers.

Here’s the problem:
When at the console, and I’m reading sonar from the transom mounted ducer, I’m showing water temps in the 80’s, which is way too high. When I switch that graph to read off of the TM mounted transducer, it shows what I believe to be the correct water temp.
However, when trying to get the front graph to display water temp when reading from the TM mounted ducer, it doesn’t show anything. Just “- -“.

So I suspect that the transom ducer is messed up and not reading water temp correctly and the cables to the front graph is messed up so the data isn’t getting to the head until from the TM ducer.

Does anyone else have other suggestions as to what could be wrong or how I could remedy the situation?