First off I’m not sure which yr or model this instrument cluster came out of. I has a tach on the left and the temp and fuel gauge are on the right. If I plug in the original(has no tach) everything works correctly. When i plug in the swap the temp gauge go to max scale and stays there. I was originally thinking the voltage connections were reversed from unit to unit. Is it possible i need a different sending unit? It has a d16y7 under the hood right now so not sure which sending unit it it has.

 

If the temp gauge works fine on your stock gauge cluster, but doesn't work properly with the replacement EX/Si type gauge cluster, it sounds like the temp gauge in the replacement gauge cluster is bad. The sending units are the same and do not need to be changed when using different gauge clusters. Try another gauge cluster.