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My car has a white coolant header tank. The Air Conditioning is working for the first time ever and that's good but when I come off the highway, I'm getting a low coolant level light on the dash. The level is not low, it's brim full and no leaks. I took the level sensor out and soapy water washed it and rinsed it. A lot of junk came out til it cleared. I can feel the float moving inside the tube. Took it for a ride and no change. BTW the car runs cool. Engine temp never goes over 82 C and that's with 90 degree summer heat. Before I had the A.C. fixed the lamp would wink on occasionally but not stay on. BUT I wasn't driving it when it was in the 90's.
So, time for a new level sensor?
 

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I think you can test the coolant level switch by removing it, hook it to an ohm meter and turn it upside down an right side up. You should see one of the two produce an open circuit and the other position a closed circuit. You might also check the wires that go to the switch for any short circuit or worn insulation. The way the wire snakes up behind the header tank can allow it to wear through the insulation from vibration or pinching.
 

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You can check the switch that way with a meter. You can also check the wires by touching them together and taking them apart to test the operation of the light. Make sure that is the correct light and it is in the right position in the binnacle. It is possible the lights got mixed up. That tank is supposed to be full when cold. Check the overflow tank inside the right rear wheel well. It should be at the full cold mark when cold. Check the hose going to the tank to make sure it is not plugged up. You can also remove and wash the overflow tank so it is easy to see the level.The float inside the level sensor could be getting stuck. It is possible to pop it apart and clean it inside. Just be careful to put it all back together exactly the way it comes apart. If you install the float upside down it will not work right..
David Teitelbaum
 

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Discussion Starter #4
Good to know it comes apart! I thought it was sealed like so many things are now.
 

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Discussion Starter #5
I think you can test the coolant level switch by removing it, hook it to an ohm meter and turn it upside down an right side up. You should see one of the two produce an open circuit and the other position a closed circuit.
Just to follow up, checked with a multimeter and it was open circuit no matter where the float was. So I decided to open it up since it seems fubar anyway. The float is at the bottom under a thin cap that comes off with a knife blade. Everything looked fine. Took the top out by putting the electrical connector end carefully in a vice and gently pulling. So, it turns out the innermost tube houses the electrodes and magnet that follows the float. That tube is supposed to be sealed completely from coolant. Mine is split, electrodes corroded falling apart. That sits in another rubber tube which is also split.
Bottom line, if you have open circuit and take the bottom off and the float is free and clean, don't go any farther, you need a new level sensor.

Thanks for all the help! Time to call the parts people.
 

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If you want , you can repair it by replacing the reed switch ( 5 cent part ) and resealing back up. I did it on my S4s .
 
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