Temperature gauge issues

[Kevin1972C20]

I need some electrical advice on my temp gauge issues.
The gauge reads max hot the second the key is turned to "ON". I can reset it to max cold with a AA battery jumped between the terminals, but again max hot (0 ohms) if key is turned to "ON".
I assume there is a ground/wiring/dash printed circuit issue somewhere but not sure. Here is what I have checked so far.
1. Replaced the sending unit and verified the old was bad (bent post and cracked center = dead)
2. Verified continuity of lead wire from sender to gauge
3. Checked ohms of sending unit (~600 ohms at 65 degrees, cold engine) however, as soon as I have the lead wire connected I get only 55 ohms.
4. Same 55 ohm reading at gauge when connected.
5. Ran seperate wire from sender to guage, bypassing all connections, still receive 55 ohm reading at gauge and sender.
6. Verified resisitor on rear of gauge is functioning (~115 ohms)
Thats where I stop and come to you all for help.
Any ideas?

[VetteVet]

What do you get on the gauge with the sender wire disconnected. It should read empty?
In order to read full hot the terminal that the sender unit wire connects to has to be grounded. It sounds like the gauge terminal is grounded , or the circuit board strip that feeds it is . You know that the terminal posts are insulated from the dash with little insulators. Below is the readings you should get at the gauge.