I feel like an idiot asking this because I looked through two dozen threads on temp gauge issues without finding my answer, but here's the deal:

'95 civic dx, z6 swapped, si cluster, water pump and thermostat replaced last week. My temp gauge shoots up to max immediately after ignition, and I feel like that is a pretty stand-out issue with one prominent solution that I haven't found yet. From my reading I gathered there are three main sensors in the cooling system. I'm hoping this problem is signature of one of those three sensors being bad, I just don't know which one. I'm going to swap out clusters tomorrow to see if that does anything...

 

Sounds to me like you have a broken wire somewhere that grounding out.

 

Hmmm possibly. I reground all the ground wires, but you're saying one of the signal wires is possibly grounding out? I'm pretty sure they're all well wrapped, but I can check tomorrow.

 

Yeah it obviously doesn't make sense that it overheats immediately after ignition so I would def re-check all wires. Sounds like a bad signal somewhere..

 

If you unplug the 1-wire temp sender unit under the distributor, does the temp gauge now read cold with the key on?

 

Sorry for the delay, I decided to replace the clutch and flywheel over the weekend. But today I unplugged the 1-wire temp sender unit and the temp gauge does in fact read cold now. I haven't gotten around to swapping clusters yet, but since unplugging that sender wire affected the reading on the gauge, does that mean the cluster is fine..? Electrical problems are not my forte...

 

The cluster is fine. Replace the sender unit.

 

Replaced the temp sender unit today with a brand new one...still the same problem. Gauge reads cold when the one-wire sender is unplugged, maxxed out when plugged in. I picked up another cluster that I could try swapping in unless you think it's something else?

 

Its definitely worth a try since you already have it.

 

The cluster is fine based on your test. The problem may be the sender unit plug. How does it look?