Signal lights, fuel gage, temp gage not working. Could it be the signal light relay? Where is it located?

Check for a blown fuse under the dash. It will be marked gauges or instruments.

Sounds loke a poor connection on the fuselinks . There is a You Tube video on how to test and repair them. https://www.youtube.com/watch?v=-SpsSRGfDQI

it sounds to me like the fuel guage sensor in the fuel tank , i think if it was fuse or relay you wouldn't have any lights on .if you car is sedan or station wagon I would likely guess that it is in boot under carpet there useuly is a plate that requires removing to inspect fuel pump , some cars have guage's and pumps as one unit. hope this helps a little.

CHECK YOUR RELAYS,FUSES

did you check your fuses???

Cooling Fan Temp Sensor is the First thing You Check (with what you have described) Cooling Fan Should ALways come On When The A/C is turned On as A/C Adds A Load to Engine, If Temp Sensor is Faulty it Will Not Give GROUND Signal to ECM >For COOLING FAN >RELAY to Give ground and turn ON The Fan.
There ARE 2 temp Sensors that Serve Different Purposes 1 is for Dash READING GAGE & Or TEMP LIGHT the Other is For ECM or Fan Relay (SAME Thing) you Said>""can disconnect the sensor and fan continues to run" < This Leads me to think you Changed the Wrong One. Not Questioning your Skills Just Here to Help.
TEMP SENSOR FOR 3.1L V6 is Located upper RH rear of engine compartment, near exhaust system. Temp SENSOR for 2.3L Engine is Located in LH rear of engine compartment.
I Hope this Helps Lead you to a NON-OVERHEATING Pontiac.
Good Luck and Have A Great Evening. rejakwilson

The fuel tank sensor is probably malfunctionibng. This sensor is located in the fuel tank. When the sensor receives a signal from the fuel tank level, this is being transferred to the fuel gauge

check your instrumentation fuse.?

The water temp sensor is located near the thermostat housing. This sensor is what tells the ECM to turn the fan on/off. The water temp sending unit is located near the same area. You know you have the correct sensor is because the water temp sensor has a 2 prong plug. The water temp sending unit only has 1 prong.

You need the voltage regulator for the fuel/temp gauge. The cluster has to be removed to change it and while your in there change out the illumination bulbs and that should take car of your lighting issue. I have enclosed a link for the regulator (I found this online, it is not my own). Just copy and paste it to your address bar.

http://www.nissanpathfinders.com/Solution2.pdf