W202 Coolant Warning Light

[A17 LTF]

My warning light came on the other day and has not gone off since. Coolant expansion tank is full of coolant and i have already taken the sensor off to have a quick check and it seems to be fine. The white plastic part inside the tank - is this a float that the sensor detects and then makes the light come on?

I have read elsewhere that the windscreen washer light is connected to the coolant warning light and that if one of them goes wrong, then the coolant warning light comes on but that did not sound right to me. Again, read elsewhere that the fan control module can go faulty and be full of water. Funny thing is the flashfloods of recent did not help and i was driving the car through some deep waters two days before the light came on. Could this possibly be the case?

At the moment me and my father have looked at changing the reservoir tank but i dont think this will solve the problem. Any advice would be much appreciated.

 

[andy27168]

Hi,
Had the same thing on my C230K, coolant light was on, header tank full, replaced the sender and it was still on, replaced the windscreen washer tank level sensor, low coolant light was extinguished.
I was told to replace the washer tank switch by a MB tech, he said due to the way they were wired this would happen.
So what you have heard is correct.

 

[dickchailey]

Wired in series with different resistances, if the washer contact goes open citcuit the coolant light comes on!

 

[A17 LTF]

Many thanks for that i will try cleaning the tank first and change the windscreen washer sensor. Am i right in thonking the float is there for checking the water level?

 

[A17 LTF]

I have now just experienced my car overheating today in traffic due to the fan not kicking in and it is now pointing towards the fan control module. Will update once this has been changed.

 

[A17 LTF]

I have messed around woth the fan control unit and noticed water leaking out of the wiring loom. Took it all out and refutted the module. Coolant light is now out but the fan is currently staying on all the time. Is this normal? Does something need to be reset or will it reset itself because the fan has not been working for quite some time?

 

[andy27168]

Are you talking about the fan control module fitted in the Passenger Side wheel arch? if so these are known to fail.
It should,nt require any codes resetting.

 

[A17 LTF]

Yes its that same module. Tried messing about with it again as it has just drained my battery by keeping the fan on permanent, regardless of the temperature of the car. Looks like it will need to be replaced

 

[A17 LTF]

Fan control module has been replaced today and the warning light has not reappeared so thats a good sign. Plus the fan has not been on yet as the car has not been running warm enough for it to kick in as of yet. Will update if any further problems arise but for now a happy chappy!

 

[andy27168]

Hi,
Glad you got it sorted.
FYI,
The fans in front of the rad are there primarily for the A/C system, they should switch on/off at varying speeds as the refrigerant pressure rises in the A/C system, if they don,t run with the A/C system its normally an indication that the refrigerant gas level is low.
They can also operate as additional cooling fans for the engine being switched on by the engine ECU, though this only occurs when engine temp. is in excess off 100 degrees.

 

[A17 LTF]

Hi,
Glad you got it sorted.
FYI,
The fans in front of the rad are there primarily for the A/C system, they should switch on/off at varying speeds as the refrigerant pressure rises in the A/C system, if they don,t run with the A/C system its normally an indication that the refrigerant gas level is low.
They can also operate as additional cooling fans for the engine being switched on by the engine ECU, though this only occurs when engine temp. is in excess off 100 degrees.

Thank you for this information as i may need it later on down the line although my current vehicle does not have aircon fitted to it but still thank you anyways. Was frustrating to say the least and it was all beacuse of this flashflood weather we have recently had!

 

[A17 LTF]

Another quick question to those in the know. What temperature should the fan kick in at? It got upto around the 90 degree mark and the fan had still not ccome on.

 

[bedwards1966]

Another quick question to those in the know. What temperature should the fan kick in at? It got upto around the 90 degree mark and the fan had still not ccome on.

This should answer that...

They can also operate as additional cooling fans for the engine being switched on by the engine ECU, though this only occurs when engine temp. is in excess off 100 degrees.

 

[A17 LTF]

G

This should answer that...

Thanks for that pal, put my mind at rest! Now have to sort the MAF now!