Coolant light on but level is ok?

Choppa7

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1995 C180 W202 is the car in question here chaps

The coolant light illuminates gradually when I start the car. The coolant level is fine and I can see the coolant when I remove the rad cap, the car temperature holds steady just over 80 when driving and I get hot air through the heaters.

All in all I think the cooling system is working ok, but could there be a level sensor which needs replacing which is throwing this error light on, on the dash?

Thanks in advance

Peter
 

television

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Do check the level in the washer bottle the 2 are wired in series
 
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Choppa7

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Thanks for that, the washer bottle level is fine too, I only recently filled it up, so I'm pretty happy with that level, interesting to know they're wired in the same circuit though!

Any other suggestions I could check?
 

Dec

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There is number 11 in the link which seems to be a coolant level switch, not clear from picture exactly where it is located on the radiator,
I think there is some kind of float switch inside radiator similar to the washer bottle as I have two wires coming from a sensor on top of radiator, unplugging the wires causes the low coolant level light to come on.

I think your initial theory is correct but as you don’t have a problem at the moment you should wait a while to see if this float unsticks itself…but keep a close eye on your temperature in the meantime.
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=202018&M=111920&GA=722421&VIN=2020182f218560&CT=F&cat=44V&SID=50&SGR=015&SGN=01

Dec
 
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Choppa7

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Thats great, thanks chaps, was just after some reassurance since I've got a 2hr drive at the weekend I dont fancy extending with some surprises lol
 

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Re the level sensor,,you could always unplug it and bridge the 2 terminals to see if it stays out
 

Dec

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I over looked one other possible explanation in my last post, if the sensor wiring plug on top of radiator is making a poor connection then this would cause the light to stay on, same as if it were disconnected, try wiggling it a little or squeeze its two lugs and pull it of and give it a bit of a clean.

As Malcolm says bridging the 2 terminals on the plug will make the light go out, if it dose, it will prove that the wiring is ok so the fault must be either a stuck float inside the radiator OR a poor connection when the plug is put back into the radiator sensor.

Dec
 
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Choppa7

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hrmmm, I unplugged the sensor at the top of teh rad last night, it loos like both connections could do with a clean since they had a white residue on them, but when I unplugged the sensor the light went out.

Am I right in thinking it should illuminate when unlpugged as the connection is broken, the same as the float breaking the connection?
 

Dec

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No it shouldn’t illuminate when unplugged, I just disconnected my own sensor and the light remains off, sorry I was confused in my last statement about that, its when you short the two wires in the plug that the light comes on.

I know you said in your first post that you checked the coolant level visually but is there any possibility that the radiator could take another liter of coolant which might then put the light out.
Looking into the radiator, it can look like it is toped up but that can be deceptive.

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I think that the washer bottle sensor needs to be looked at and unplugging
 

c class sport

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I have the same problem, stuck what to do now though, the coolant level and temprature are fine but the coolant level light remains on what ever i try, i have replaced the coolant level sensor today and whether it is plugged in or out the light remains on???
 

bouncer

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Had the same problem with my old W202. it was the rad sensor.
The resistance was way off.
Rad sensor used to put the washer level light on as well.
They are only cheap. and 10 seconds to change.

sTeVe
 

c class sport

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this morning the coolant light wasn't on, as i left Nottingham for Newcastle the coolant level light came on and stayed on all the way back, I have cleaned all the contacts, cleaned the jelly off the washer bottle sensor and double checked all levels, the light remains on, even with the rad sensor and washer bottle sensor unplugged the coolant light stays on, is this right? is it worth replacing the washer bottle sensor, I have already replaced the rad sensor,
thanks...
 

c class sport

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Hi, I also replaced the washer bottle sensor today, took a gamble with a breakers yard £5 sensor, am glad to say, it has worked and resolved my problem, Thanks everyone for pointing me in the right direction. :)
 

c class sport

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Hasn't worked guys, the light has come back on, I have discovered though if I remove the washer bottle sensor and let it drain the light then switches over to the washer bottle level light which I assume is correct, as soon as the sensor goes back into the water and fills up it switch back to the radiator light???
 

lukejr

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Same Issue

I just had the coolant light problem this week. I topped up the coolant, but the light doesn't go off right away.

So when I start my car the light is on, after driving for 5-10 mins and the engine temps is just over 80 the coolant light turns off. It now does this for all trips.

Could this be an electrical problem, I know the wiring in the W202 isn't the best.
 


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