LOW COOLANT Warning Light

[MSG2004]

Hello,

My 53 plate, 180k, Auto - the low coolant warning light came on a few weeks ago as i drove the 2 miles to work, took about 15 mins, weather was cold - checked collant, it was at the right level.

The same thing happened yesterday, approx 4 mile drive,a bit warmer and 15/20 min drive - light came on when i switched off as before.

About 6 months ago, it came on whilst driving on the motor way at about 70 mph for an hour.

About 2 years ago, stuck in traffic on a hot day, the low coolant light came on and temp was high, so i turned on fans and temp went to normal - as i was going to the dealership for a service, they said as i expected, nothing wrong and car then was inder warranty.

Model W203

All help appreciated.

Thanks

 

[recycled]

coolant level sensor

 

[television]

To me it sounds like a faulty sensor

 

[BlackC55]

thirded.

 

[MSG2004]

Thanks all

BTW - engine ino runs a bit hot but done that since purchased more than 3 years ago - car was 6 months old - runs normally in mild weather at approx 90.

Is the sensor easy to replace and approx cost of item or to have it done?

Thanks

 

[recycled]

£10-£15 easy to replace. disconnect plug,twist and turn like a light bulb, replace and plug back in

 

[television]

http://www.detali.ru/cat/oem_mb2.as...605716.628&CT=F&cat=69P&SID=50&SGR=165&SGN=02

190 in the link

 

[MSG2004]

thanks

 

[dickchailey]

Not sure about W203's but on CLK's the coolant sensor is in series with the washer bottle sensor but with diffferent resistors across the contacts. If the washer sensor goes open circuit the coolant warning comes on!!!

 

[television]

Not sure about W203's but on CLK's the coolant sensor is in series with the washer bottle sensor but with diffferent resistors across the contacts. If the washer sensor goes open circuit the coolant warning comes on!!!

This can be true and other odd things on MB the fan on constantly can come up with low washer lamp on a 202.

Its a minefield out there

 

[GazCaff]

I had a phantom low coolant warning for quite a few weeks over the Christmas period. I changed the sensor, but the warning light stayed on and testing the circuit with a multimeter left me non the wiser. It may sound irresponsible but in the end I removed the warning bulb.

I've got my head under the bonnet at least once a week anyway, I'm not worried about overheating the engine.

 

[dickchailey]

It's not that difficiult to test. One sensor has a resistor of 110 (coolant)and the other 174 (washer)across the contacts. If the resistor has failed the sensor will be open circuit. If the level is low the switch shorts out the resistor. If the resistor in the washer bottle goes open circuit the circuit fail to work as it should and the coolant warning comes on. Muitimeter should sort it out.

 

[GazCaff]

When I tested the circuit, the coolant sensor was showing about 118ohms. I cannot remember what the low washer sensor was reading, but it came on today to show low washer fluid. Is it possible for it to be at fault and still apparently work properly?

 

[dickchailey]

After I replaced my washer sensor I smashed it open and found it was badly corroded and the resistor fell apart. If you could find a resistor between R170 and say R200 and push the ends into the connector you could leave it like that for a few weeks to see if you have a cure.