I have a 350SDL that I have redone the entire cooling system from the radiator to the hoses to the heater core, water pump, temp switch, etc.

the car runs well and I drove it for the first time in an extended drive when it was more than 101 degrees outside.

The car did get up just a little above 100 on the temp gauge, but had the A/C on and it was HOT outside.

The coolant level light went on (new resevoir and level switch already installed). The car did not seem to heat up any more, but the exterior temp indicator went as high as 116 (and it is close to the radiator).

I checked coolant level in the resevior and it was fine.

I turned the car off to gas up and when I turned it back on the light was out for a few seconds and then came back on.

I got home and parked it. Later I started it to move it and the level indicator did not come on. The car was no longer extremely hot. I am thinking it may have something to do with the temperature even though it is a coolant level indicator.

Anyone see anything like this, or have any idea what it might be?

Always check your grounds. they can cause odd lights to go off, I dont know if there's more sensors on a S350 then there are on the regular 603 but you might have a defective coolant level switch.

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

I thought about both of those and am going to check them. I did take the dash off to do the evaporator, so it is possible a ground is not tight. I am also going to check the switch, but because it only came on under high temp conditions (both engine and environment) and did so consistently, I am thinking it might be something else.

It is easy to check out wiring or to confirm an intermittent ground.

1) Remove the plug to the sensor ( at the front of the expansion tank ) and the light should be off. Drive around for a while to make sure it stays off. If it comes on then there is a wiring fault somewhere.

2) Jump the plug and the light should be on. Make sure you have enough coolant and drive around for a while also. It it goes off then there is a wiring fault somewhere.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Any ideas what if it could be something other than the fluid level if the light it legit?

In looking at the wiring diagram, the switch is also connected to the wiper fluid switch and the front brake contact sensors (as strange as that sounds...)

For the coolant level? No.. there should be a separate Sensor for each of them... the might go to a Central source like a computer maybe... but their functions shouldn't be related to each other

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed