charliediss

I pirated this from somewhere on the internet, it is a pretty good explanation of a CLS.

A Coolant Level Sensor is like a multimeter which measures resistance of a certain amount of water.

Water has conductive minerals in it therefore conducts electricity. A certain amount of water has a certain resistance to electricity.

Fixing this voltage at, for clarity's sake, 12.0v, we can change the resistance of the conductor carrying this 12v by adding more water (and the minerals which conduct in it), or taking water away.

like a fuel guage, At a certain resistance, the sensor will give off a certain reading. The fuel guage uses the change in this reading to move a needle, the coolant temp sensor uses this reading to trigger events in the cars ECU (Electronic Control Unit) or BCM (Body Control Module). The ECU or BCM will then light the dashboard warning for the Coolant Low Warning and log A DEC (Diagnostic Error Code) and probably also flag the CHECK ENGINE LIGHT on your dash.

When the coolant is topped up again, the coolant sensor sends a different signal as it sees a different resistance, and turns off the dash light(s).



Read more: http://wiki.answers.com/Q/How_coolan...#ixzz1WwTcWM5H

Injuneer

Interesting, but the LT1 coolant level switch works nothing like what is described. There is no connecection to the ECM, there is no BCM on a 93-95, the ECM does not turn on the low coolant light based on the coolant temp sensor, etc. There is no diagnostic code.

The lack of conductivity on the level sensor causes it to switch to ground, and the ground completes the circuit that turns on the dash light. Simple as that. In the 96/97 cars, when the BCM was added, the level sensor also causes the BCM to "latch" to ground on the circuit, so the low coolant light stays on, even if the sensor opens the ground.

Water has a high resistivity (low conductivity). Pure water has an extremely high resistivity. But we're talking about coolant, which is a 50/50 mix (or similar) of water/ethylene glycol, which has a much lower resistivity.

shoebox

There also is a latching function in the pre-BCM models. It is contained in the RAP module (RAP was later incorporated into the BCM). The latching function is to keep the low coolant lamp on even if the sensor value returns to a non alarm status during a drive cycle, making sure you don't miss the indicator lamp.

graeme

Hmmm I still think this thing is a Thermistor NTC . I got an X-Ray done on this device and will post this soon (result not conclusive), my next step is to slowly grind the epoxy away from the components and with any luck I will be able to put this question to rest. You can not say im not trying .

Graeme in OZ

Psycho

Let us know. Maybe there is a way to R&R an old one to make them work.

graeme

http://imageshack.us/photo/my-images/827/p9070322.jpg/

above second link is a better shot sorry about that, guess im not used to posting pictures.

I think this link should work, let me know if not.
As you can see there are components in there resistors etc, but it did not show the circuit tracks unfortunately. Still working on this and even tried to contact GM about a general description of these COOLANT LEVEL SENSORS, but they will not correspond to those outside of the USA. .
Thanks GM, they did give me the Australian Holden help line, but when I rang them they had no information on these cars and could not access any from the US either .

Graeme In OZ all alone so it seems !!

graeme

This has really given me a headache, I think I could be suffering from a slight case of Asperger's syndrome (look it up) I just can not let this rest. I contacted RockAuto about returning the low level sensor I bought off them (as it too gave the low coolant light on dash when radiator was full) and they had no problem in doing so, I took there sensor out tonight and put the old one back in so I could still use the Camaro until I got a new one from them. I asked them for a different brand, will have to wait for an email from them to see if they will or not.
Anyway like I said, I put the old sensor in and topped up the coolant level, then ran car and checked for any leaks. I then noticed there was NO Low Coolant Light on the dash display ???. so I took it for a half hour drive and still no light was displayed. This is somewhat confusing, I had another think about this and could not come up with a conclusion, one thing I did do last week was I checked the Body Control Module for any history. There was none, but I put in the code to clear any codes anyway !, could this BCM cause a latch signal when the coolant level sensor was ok ???.
If anyone else has this problem, I wonder if you too might try clearing any fault codes from the BCM and let me know what happens !
Graeme in OZ