I have a 1990 GXL with a LS1 swap. All of my dash gauges were working for over a year and now my temp gauge stopped working. I have a second cluster so I swapped the gauges and the temp gauge still doesn't work. My question is, What type signal does the sensor send to the gauge?
There are three screws. I assume one is power, one is ground and one is a signal from the sensor.
When I put my test light on the three screws, I get:
screw 1 - a bright light I am guessing power 12V
screw 2 - no light I am guessing ground
screw 3 - a dim light I am guessing the signal or a short. What type signal does the sensor send to the gauge?

 

From the 89-91 FSM, grounding the sending unit wire through a 13 ohm resistor gauge should display 130C (266F) and through a 154 ohm resistor gauge should display 50C (122F). I am assuming that 50C and 130C are respectively the bottom and top of the operating region or hatch marked portion of gauge. Sending unit acts as a variable ground dependent on coolant temperature. Sending unit should have a resistance of 57.7-49.3 ohms at 80C (176F). Here is reference: https://www.rotaryheads.com/PDF/2nd_...cal_system.pdf

 

Thank you. I’m going to test it this evening. I hope that’s all it is. I have ordered another temp sensor sender just in case.

 

i put a potentiometer on something (i think its in an enclosure?), and put a **** on it. then i measured the resistances, and marked the **** position. then you can put one side to ground, one side to the car and turn the ****, and the gauge moves accordingly. the S5 one is weird!

you could do it with a switch and resistors too, i just used what i had laying around

 

Yeah, that's a good idea too, but if you're just doing a one time check it seems like a lot of extra effort to go through.

 

it was neat, and i had the bits, but yeah its way overkill for just testing it once