Throughout the later years of the Fox chassis, the low coolant sensors had some differences that caused confusion for some engine builds. Follow the article below, and we will cover everything you need to know!
Being able to monitor your coolant levels is essential for any Mustang owner. For most of the OEM Fox Body Mustangs, these cars came equipped with a dash light that turned on if the coolant within the reservoir was too low. This safety feature allowed the driver to know if it was time to pull over and top off the engine coolant without constantly having to pop the hood to visually inspect the tank.
I would like to note that some of the 5.0L Mustangs were not equipped with this factory sensor. So you can check over your engine bay for the factory wiring harness that we will cover later in the article. Also, the overflow tank has a slightly different design as well.
The 1987-1989 low coolant sensor used a bulky float design. While this design worked fine, it used up some of the internal room on the overflow tank for fluid capacity. This style sensor can sometimes be a pain to remove from the tank. This caused overfilling and spilling issues in most cases. The internal float design was a simple switch that, when full, kept the dash light from emitting. Once the fluid level dropped low enough, the float would drop, and this would cause the light to turn on inside of the vehicle's dash. One common problem with these sensors was build-up around the float, causing it to stick or cracks in the float that would not allow it to raise up to the full position. The wiring of this sensor was a simple 2-wire design.
For years, this sensor was never reproduced. At the current time when this article was written, our friends over at Daniel Carpenter Mustang Restoration Parts had just released a newer version of this outdated sensor.
The 1990-1993 low coolant sensor had a new redesign change. This new sensor used a simple 2-pronged end that used the coolant and water mixture within the tank to complete the circuit. As long as the proper amount of fluid is present within the reservoir, the light would not pop up on the dash. This new design also solved the bulky nature of the previous model, and this one was much easier to remove from the tank for fill-ups. Ford carried this same design over to the new body style change on the SN95 1994-1995 5.0L GT and Cobra. This sensor featured a 3-wire connector for the dash light.
One common issue with the 1990-1993 design was corrosion on the 2-pronged end. Over time, these tips acquired build up, and this can cause intermittent light issues on the dash. Normally, cleaning these tips on the sensor helped, but ultimately, replacement of the sensor was needed.