Ok, I have an intermittent Low Coolant dash light. I have tried cleaning the leads, replacing the cap/sensor with a used one and even replacing the sensor with a new one (they are the same as the mustang). It usually comes on after a little bit of driving ... sometimes it's dimmer than other times (though that could be in my head). Sometimes it goes out (hooray). It's never low on coolant in the reservoir tank. Any ideas (other than just unplugging that sensor)? (1990 MTX, 45k miles) Thanks, all!
Intermittent Low Coolant Light
- Thread starter Nick0127
- Start date
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SHOrod
Torrie Tuned
Have you confirmed that on your car leaving the sensor unplugged will allow the low coolant light to remain off? Since you mentioned it might be dimmer sometimes, that makes me wonder if maybe you have a wiring issue somewhere, especially considering that you've tried replacing the sensor already.
Also, when you say you've tried cleaning the leads, did you remove the sensor from the tank and clean the internal portion of the sensor, or just the external connections?
-Rod
Also, when you say you've tried cleaning the leads, did you remove the sensor from the tank and clean the internal portion of the sensor, or just the external connections?
-Rod
Thanks … disconnecting the sensor completely keeps the dash light off. I only cleaned the sensor leads that stick into the coolant. But what’s odd is that the brand new one has the same behavior!
SHOrod
Torrie Tuned
I've had luck with removing the sensor and cleaning the portion of sensor that resides inside the tank, but you're right, it seems odd the new one would have the same behavior as the old. It sill might be worth a try, along with making sure your coolant level is not actually low. 
-Rod
-Rod
The sensor is electrically the same as the Mustang (and Thunderbird), but the various versions have a different length of sensor wire depending on the depth of the tank. The coolant overflow tank on the SHO is unusually deep. You may have checked this already, but I thought the Mustang sensor was shorter, so the warning may activate earlier than intended.
I agree with shaldaya that the sensor design of that era makes it prone to false readings. Mustang owners have also noticed this fault.
I agree with shaldaya that the sensor design of that era makes it prone to false readings. Mustang owners have also noticed this fault.
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SHOmont
Member
Common problem in German cars, but more annoying since the sensor is tied to the ECU…..just add salt to change the coolant conductivity……. https://www.slkworld.com/threads/resolved-low-coolant-and-low-washer-warning-no-fault.554618/
Ok so it seems the new sensor just had to settle in. The light is gone. That mustang part worked!
Came back - I gave up and unplugged it. IT's a mystery to me why a brand new sensor would do this. I guess it's reading more than the level - maybe the chemical make up of the coolant?
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