Ive got an 85 4runner SR5, factory coolant temp gauge in the cluster.

I just did a 5MGE engine swap.

Before the gauge would sit dead center while running all the time, clearly before it has heated up. (I think it drops to 0 when the truck is shut off)

Figured there was an issue with wiring or the sensor or something.

Now that I've done the swap though, those wires are no longer hooked up - still sits dead center.
Where should I be looking for the issue? Is this a gauge problem, could a wire be shorted out causing this?

 

the connector or the sending unit could be corroded or the wire could be grounded someplace.

when you turn the key off does the gauge go all the way to left??

I have a few disconnected temp gauges that once in a while will do the same thing which means some place the circuit is getting a ground