Brakes 1990, low coolant light riddle

bdemat

Member
Sep 22, 2018
10
1
13
Acworth ga
Hello everyone, riddle me this, I have a 1990 5.0. Low coolant light always coming on. Coolant is fine, constantly checked it to make sure. Replaced the low coolant sensor twice with new lmr one. Replaced the connector, still on. When I unplug the sensor light goes out. It's not usually on when I just start the car but it will come after a mile or so
 
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nickyb

Active Member
Apr 3, 2009
274
89
38
nevada
i just unpluged mine and check it with all my fluids once a week.i mean do we really need an idiot light?whats next sensors telling us to check our air in the tires?another one to tell us to change our oil?,put our seatbelts on?At this rate the cars will be driving themselves!
 
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Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,061
9,207
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Massachusetts
Unplug it. They are notorious for false readings. They only read the level in the bottle so if you see coolant in the bottle you are fine.
 

bdemat

Member
Sep 22, 2018
10
1
13
Acworth ga
Thanks guys for the advice but I am the type of person that has to have everything work the way it's supposed to. I know it's not that big a deal but I will mess with it a little longer to figure it out.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,061
9,207
224
Massachusetts
Thanks guys for the advice but I am the type of person that has to have everything work the way it's supposed to. I know it's not that big a deal but I will mess with it a little longer to figure it out.
I'm the same way so I understand your plight. Usually it is the sensors but as a check you can check the wiring to make sure it's in good shape. Red will be your power and black is the ground. With engine on make sure you have a consistent 12v here. The blue wire is your return to cluster. Closing the sensor (low coolant) will trip the light which is why unplugging it will keep light permanently off
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
16,827
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polk county florida
IMG_20181223_101244.jpg

This for an 89 and may be hard to read, it shows how to test the circuit, wire colors ma be different but it will give you an idea of what to look for, hope this helps
i like stuff to work right too!
 

bdemat

Member
Sep 22, 2018
10
1
13
Acworth ga
I'm the same way so I understand your plight. Usually it is the sensors but as a check you can check the wiring to make sure it's in good shape. Red will be your power and black is the ground. With engine on make sure you have a consistent 12v here. The blue wire is your return to cluster. Closing the sensor (low coolant) will trip the light which is why unplugging it will keep light permanently off[/QU
I'm the same way so I understand your plight. Usually it is the sensors but as a check you can check the wiring to make sure it's in good shape. Red will be your power and black is the ground. With engine on make sure you have a consistent 12v here. The blue wire is your return to cluster. Closing the sensor (low coolant) will trip the light which is why unplugging it will keep light permanently off[/QUO
 
Last edited:

4ever91

New Member
May 4, 2019
4
0
1
58
Valencia, CA
I will test that and see what happens, Thanks for the help and the pics!
Did you resolve the low coolant light yet? My 91 LX exact same. New radiator. New sensor and pigtail connector from LMR. Coolant levels in both the XS bottle and radiator look fine. No leaks. Not overheating. But low coolant idiot light is on and stays on. I’m tempted to disconnect the sensor and live free. How much more nonsense does Ford want us to go through ?
 

bdemat

Member
Sep 22, 2018
10
1
13
Acworth ga
Did you resolve the low coolant light yet? My 91 LX exact same. New radiator. New sensor and pigtail connector from LMR. Coolant levels in both the XS bottle and radiator look fine. No leaks. Not overheating. But low coolant idiot light is on and stays on. I’m tempted to disconnect the sensor and live free. How much more nonsense does Ford want us to go through ?
Yes and
Did you resolve the low coolant light yet? My 91 LX exact same. New radiator. New sensor and pigtail connector from LMR. Coolant levels in both the XS bottle and radiator look fine. No leaks. Not overheating. But low coolant idiot light is on and stays on. I’m tempted to disconnect the sensor and live free. How much more nonsense does Ford want us to go through ?
Yes and no. I found the ground wire coming off the connector plug and grounded it to the frame. The light stayed on for about two or three days after that and then I haven't seen it since. Don't actually know if that fixed it or if it's just went out. Either way it's gone.
 
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