No Fiero ever came with a low coolant sensor, so I added one to mine. I give some credit to Oliver Scholz because I saw him add the light first. He did it differently than me, so here’s my write up on what I did.
I started with an ACDELCO 19299321 Coolant Level Sensor. This is an expensive sensor, relative to a typical simple switching sensor. The reason for using this sensor is that it also does the bulb check on its own. The circuit is simply …
Battery –> LED –> Resistor –> Sensor –> Ground
Then I had a better welder than me modify the 3×00 coolant line on the top of the water pump to mount the sensor. Also, he tried to modify the top of the tube so that I could use it as a fill point. So, this one tube, which was only a bleeder, would now be a bleeder point, a fill point, and a low coolant sensor mount. Once I installed the new tube I quickly realized that it is still in a hard spot to reach. You need a funnel to reach it at all. Oh well.
It is also a little close to the valve cover, but installation was very easy. Wiring the sensor in was the easiest part of this addition. In the C500 connector (the weird bulky connector with a 5.5mm bolt in the middle near the battery), pin D3, there was already a wire for the old over temperature sensor to the cluster. I just added a wire to that and then connected it to pin B of the 3 pin coolant level sensor connector. Then, pin C from the sensor I ran to the ring terminal ground in the C500 harness that bolts to the engine block. It is all wrapped up the in C500 harness nice and clean.
Here is a video of the gauge cluster when turning the key on.
In the video above, notice that when the key is turned to ignition that the over temp bulb gets really bright for a half second. Then it gets dim and stays dim. It is an LED that I rigged up just like the LED for my door ajar indicator. It is really easy to distinguish between the bright and the dim brightness too. Also, the dim appearance is very dim. I think it is nice to have a suddle reminder that the wiring and sensor are still working all the time.
The funny part is that the same day I installed this sensor, I blew out a coolant hose. The complete white-out behind me was more of warning sign than any light bulb in my dash though (the light did work). Thanks to a friend I was only stranded for about 30 minutes. I was able to cut the hose one inch shorter, clamp it, fill it and drive it. That was a new hose from the engine swap too! Not one of the old hoses on the car.
Here is the wiring diagram and connector info for the 1999 Buick Regal, which uses this coolant level sensor:
According to RockAuto.com, you can find this sensor in all of these vehicles, on the passenger side of the radiator:
BUICK CENTURY 1997-2002
BUICK REGAL 1991-2002
CHEVROLET CAMARO 1994-2001
CHEVROLET IMPALA 2000-2002
CHEVROLET LUMINA 1991-2001
CHEVROLET LUMINA APV 1996
CHEVROLET MONTE CARLO 1995-2002
CHEVROLET VENTURE 1997-2000
OLDSMOBILE CUTLASS SUPREME 1991-1997
OLDSMOBILE INTRIGUE 1998-1999
OLDSMOBILE SILHOUETTE 1996-2000
PONTIAC FIREBIRD 1994-2001
PONTIAC GRAND PRIX 1991-2002
PONTIAC MONTANA 1999-2001
PONTIAC TRANS SPORT 1996-1998