Low Coolant Sensor Schematic
Thread Starter
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
Low Coolant Sensor Schematic
I found this module in my dash right behind the fuse panel. It turned out to be the low coolant indicator module. The box was covered with sticky goo from being taped to the wiring harness and when I cleaned it up the part number that was rubber stamped on there got erased so I added the label.
The back side:
This is an interesting circuit. U1-E & U1-F are an oscillator that operates at about 5 KHz. The circuit filters this out and applies it to the transistor, which turns on the low coolant indicator lamp. When the low coolant sensor is submerged it basically shorts out the output of the oscillator and turns off the transistor, so the low coolant lamp goes out. The 160K resistor and 10uF capacitor put in a delay of a couple of seconds, which keeps the lamp from blinking rapidly when the coolant is sloshing around the sensor. I think it's interesting that the coolant is the return line to ground for the one wire sensor. None of the components have mysterious GM part numbers, so it should be easy to repair this module.
The back side:
This is an interesting circuit. U1-E & U1-F are an oscillator that operates at about 5 KHz. The circuit filters this out and applies it to the transistor, which turns on the low coolant indicator lamp. When the low coolant sensor is submerged it basically shorts out the output of the oscillator and turns off the transistor, so the low coolant lamp goes out. The 160K resistor and 10uF capacitor put in a delay of a couple of seconds, which keeps the lamp from blinking rapidly when the coolant is sloshing around the sensor. I think it's interesting that the coolant is the return line to ground for the one wire sensor. None of the components have mysterious GM part numbers, so it should be easy to repair this module.
Last edited by Cliff Harris; Dec 28, 2011 at 02:54 AM.
Thread Starter
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
That's cool. I like the color coding. Did you draw that?
I didn't calculate the time constant. I just guessed based on what I saw happening on the scope.
One thing I noticed: 100M is not a standard resistor value. They only go up to 20M.
I didn't calculate the time constant. I just guessed based on what I saw happening on the scope.
One thing I noticed: 100M is not a standard resistor value. They only go up to 20M.
Slingshot
Joined: Dec 2001
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From: Charlotte NC
I don't know about the resistor value.
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OOPS post on wrong thread. LOL
Last edited by kenmohr; Apr 18, 2018 at 06:48 AM.
