explain coolant low sensor
Thread Starter
Racer
Joined: Oct 2002
Posts: 470
Likes: 1
From: Kingwood TX
explain coolant low sensor
I have a low coolant lite on my 91 L 98. I Pulled the sensor out of the bottom of expansion tank. Sensor looks like cheap xmas lite bulb with 2 wires exposed on top. only mention of it in "FSM " is section #8 showing circuit schematic. My electronic skills are vacuum tube era.
Anyone familiar with this small glass tube ,how it works & what its proper name is.? Thank You.
Warren
Anyone familiar with this small glass tube ,how it works & what its proper name is.? Thank You.
Warren
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
Likes: 71
From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Coolant level sensor, I believe is the name. It works off of a voltage signal from the ECM. And the amount of voltage returned informs the computer as to whether the sensor is immersed in coolant or not. Failure of these is not uncommon, especially as a vehicle ages.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The sensor makes contact with the coolant which causes electrical conductivity. If no conduction occurs, then no coolant is in contact and the low coolant light will be lit by the circuit that is activated by high sensor resistance.
Melting Slicks
Joined: Oct 2004
Posts: 2,283
Likes: 0
From: Leeds Alabama
Long story short, if the light only comes on and off for a while, the filler neck where the sensor is located is ABOVE the engine waterline by design. Park your car on a slight hill nose foward. Run the car will cap not tight until motor is warm (not hot) take off cap run engine at 1500 rpm until warm fill radiator with water until the BRIM OF NECK while engine is at 1500 rpms do not let drop below. When coolant is full (basically running over) put the cap on radiator, that will eliminate the two inch air pocket on top of the filler neck and radiator. This will cure an intermittant coolant light problem assuming no leaks exists.
