Question : Temp Guage Not Working

[94GPGTP]

1990 Pontiac Turbo Grand Prix 5 Speed Swapped

I replaced the single green wire sensor with a new one before installing my new engine.. Now that the car is running the temp guage does not work.. With the key on i ground the dark green wire on the car for the guage to peg 260 annd it does nothing i can see the interior lights dim and then i had smoke and the wire i was using to ground was hot.. Im going crazy now and i tear the dash down and find that C4 in the cluster plug is for the coolant temp sender.. I decided to test if power was getting in this wire because i dont know if it gets power or not but i ground the meter to the car and turn the key on and touch my lead to C4 and i have 12 volts.. That could be why i had smoke and my grounding wire was hot because i was making a short.. well i have been tracing this wire down all day after work and find out its inside the car thats causing the 12 volts. i dont know what or where the wire is yet on the passenger kick panel but any help is appreciated.. I ohmed the wire from the sensor to the cluster and its good with the key off.. like i said earlier i dont think it is suppose to get 12 volts if its reading OHMS from the sender..
Any help is appreciated as i want to solve this problem among others..

[bszopi]

Not sure where you got the idea that it is supposed to be grounded.

DESCRIPTION
This temperature indicating system consists of a sending unit, located on the cylinder head, electrical temperature gauge and an instrument voltage regulator.

OPERATION
As engine temperature increases or decreases, the resistance of the sending unit changes, in turn controlling current flow through the gauge. When engine temperature is low sending unit resistance is high, current flow through the gauge is restricted, and the gauge pointer remains against the stop or moves very little. As engine temperature increases sending unit resistance decreases and current flow through the gauge increases, resulting in increased pointer movement.

Troubleshooting for the electrical temperature indicating system is the same as for the electrical oil pressure indicating system.

The gauge reads the current going to the sensor. As the resistance of the sensor changes due to changes in temperature, this causes the gauge to fluctuate.

[94GPGTP]

Not sure where you got the idea that it is supposed to be grounded.



The gauge reads the current going to the sensor. As the resistance of the sensor changes due to changes in temperature, this causes the gauge to fluctuate.

In the service manual it states to test if the guage works ground the dark green wire in the engine bay and the guage should peg to 260 that tells you if the guage works or not and to tell you if you have a bad sensor.. Well when i ground that dark green wire my jumper wire im using to gound it with gets hot and the guage does not move..