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Discussion Starter #1
my coolant light goes on soon as i start the car and stays on. The coolant level is at the correct level (cold level).

I assumed the coolant level sensor was faulty and needed changing, until i noticed coolant temp gauge only reaching 60 this morning and then hovering between the 90-100 mark on retuning from work.

i did have a problem with the washer bottle sensor light (fixed by simply unplugging and plugging the connection to the sensor).

Could this be a coolant temp sensor problem?

if so
1. is it a easy fix?
2. where is it located?

or a coolant level sensor problem?

Thanks
 

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02 ML320 06 ML500
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16,928 Posts
The owner's manual says that the Coolant Level light will illuminate if (of course) the level is low or the coolant temperature is high.

If there was just a problem with the the level sensor, it would have no effect whatsoever on how the temp. gauge reads. But a false signal from the Coolant Temp. Sensor could trigger the level light.

It is not known where your Temp. Sensor is, but on the US model it is directly on the top/front of the engine, marked B11/4 in the diagram. It is a two wire sensor and very easy to change. With an Ohm meter you can compare the values as outlined in the chart.

There are two possibilities. You could have a faulty thermostat or your elec. fans are not turning on.
 

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Discussion Starter #3
just to let everyone know the light problem has been solved.
The problem was an over voltage fuse had blown (sits on the positive terminal on the battery-£10 from mercedes).
 

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ML270CDI Auto Luxury 2000 Phase 1 W163
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After repairs on my 2000 ML270 including engine rebuild and wholesale sensor swaps, my coolant light came on. It turned out to be a 7.5 amp fuse in the loom behind the engine fuse box near the ECU which has something to do with the Radiator fan. To get to it just remove the cover behind the fuse box. Swapped it out and it blew again when the engine reached temp. Swapped it for a 10 amp fuse problem solved!
 

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02 ML320 06 ML500
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16,928 Posts
After repairs on my 2000 ML270 including engine rebuild and wholesale sensor swaps, my coolant light came on. It turned out to be a 7.5 amp fuse in the loom behind the engine fuse box near the ECU which has something to do with the Radiator fan. To get to it just remove the cover behind the fuse box. Swapped it out and it blew again when the engine reached temp. Swapped it for a 10 amp fuse problem solved!
Using a higher amperage fuse is a recipe for disaster. You are only masking the problem by using a higher fuse.
 

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ML270CDI Auto Luxury 2000 Phase 1 W163
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Using a higher amperage fuse is a recipe for disaster. You are only masking the problem by using a higher fuse.

The main radiator fan has not been used for 2 years while the car was idle and in pieces in the open hence it drawing higher current. Iv'e cleaned the motor as best I can but I think it needs bedding in again and I'll switch back to a 7.5 amp otherwise its a new fan!.
 

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02 ML320 06 ML500
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16,928 Posts
We do not have any wiring diagrams for Euro. models, but all suction fans run off of a 100 amp. fuse.

What this 7.5 amp fuse controls is the issue.
 

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ML270CDI Auto Luxury 2000 Phase 1 W163
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We do not have any wiring diagrams for Euro. models, but all suction fans run off of a 100 amp. fuse.

What this 7.5 amp fuse controls is the issue.
It seems to be a factory fit but given the year (2000) and hidden location away from either fuse panel under the ECU/loom cover, I think it's an addition which is specific for the ML270CDI. There are some other electrical issues with the loom including the passenger seat when moved causing SRS light illumination. I am lining up a few days to go over the loom section by section with a multimeter to find breaks and bad contacts.

In the meantime I will be running the engine and doing some more runs after the overhaul I did and when it's up to running temp when I get back I'll change it back to a 7.5 and cross my fingers
 
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