hello. i just installed a 02 wrx cluster into my04, everything is what i want it to be, everything lights up and functions BUT the water temp gauge is not working. does anybody know why?

2 reasons why i changed to 02 cluster:

1. wanted tach on side, cause i have a 320mm wheel and can't see the centre gauge
2. wanted to change it to amber, but didn't want to touch my stock cluster.

the 3 harness are in all they way, the gas tank gauge works - and i think it's the same harness as the temp, so i don't know what's wrong - please point me in the right direction!