The low coolant light is on the radiator full
why ?

 

There are old threads on this, the sensor below the tank seems to cause problems if I recall properly.

 

The coolant level must be high up in the reservoir tank, like about one inch from the top, to be properly filled. The light will also activate if the coolant temperature is too high.
I would first add some distilled water into the reservoir to be certain you are topped off, before troubleshooting the sensor.
PS you got me while I was typing 180.

 

WRONG. It is not the "low coolant light". It is the "General cooling system alarm light" and your owner's manual essentially calls it that, when it tells you to "go right to a dealer if the light comes on".
Of course, taking a Crossfire to a dealer is foolish - see my sigline below.


ANYWAY:
IT comes on when:

The coolant in the tank is low.
The sensor in the tank is bad.
The water temp is above about 230F (gauge will show this as well).
The engine cooling fan motor is defective.
The fan control module is either defective OR senses an issue with the fan motor.
Communication is lost between the Fan Module and ECM (in this case, the fan will be running at high speed).

There may be other reasons for the light to come on that they don't tell us about.
My money is on a bad sensor in the tank, but I"m not standing next to your car.....

 

So, I have read all of the information in thread and have a similar problem. Light comes on, but temp seems to be fine, and coolant level is fine (to to white peg in tank when cold). SInce the engine temp is consistently staying good, am I danger of causing damage if I continue to drive? It seems that the light goes out after some time.

Thanks,
Castokrk

 

You have a bad coolant level sensor. No big deal.

 

Hi Pizzaguy - so, I realized that the fan is not coming on at all hence it runs hot just sitting at idle. I replaced the fan and still no luck. 50 AMP fuse or do you still think it is the sensor? I think that the fuse is blown because I can not read the "50" on it like I can on the other one or on the 200 in the same box, but am not sure as I have never seen these mounted type fuses before.. thoughts???

 

Well, if you fan is not coming in, THAT is why the damn light is on. The ECU is not getting the response it wants from the Fan Control Module.

Check the 50 amp fuse, if it's OK, order a FCM. They are EASY to change, two bolts and the connector is a quick-connect thing - super easy. Search "2003 Mercedes SLK320 Fan Control Module".

 

thanks for the help!!!

 

7/15/2021: Hi pizzaguy. fan seems to be working after the fuse replacement. Same day I got the fan working, car went into "limp mode". Code was something throttle body or pedal position, type of error. Reset and no issues since on that front. The AC just stopped blowing cold on my way home from the shop. Question: - can this be related to the FCM? (the AC that is), or am I probably looking at the HVAC controller in the dash? It seems odd that I am having these sequential failures all since the fan went bad. If I lived somewhere a bit cooler, I wouldn't worry about the AC, but South Carolina in July & August is a bit "warm"!! Any idea would be helpful. Mu local/usual mechanic is stumped (and he is good). I may try Zachery down in Columbia if you don't have an idea.
Thanks
castokrk

 

Hello, Pizza Guy is the best no question on that front but I will try to help with the AC system issue.
1) Is the a/c compressor clutch engaging?
2) If not check that fuse as well.
2) If it is engaging are the lines getting cold to the touch?
3) I looked at the schematic for the FCM question. I did see where the FCM gives a signal to the PCM. PG 546 or 7-2.Then the PCM communicates with the ECU and AHCM. You can download the service manual( available on this forum) PG.4130 or 24-1 starts the A/C troubleshooting information and the schematic can be found on PG. 4189 or 24-60.
If it makes you feel better within three months I had a top hydraulic cylinder go bad, CSP/SSM module/wiring harness, alternator,A/C controller, TMPS sensors replaced, and I just repaired the valve cover breather due to it leaking oil. This is all in a very well cared for garage kept 05 SRT with 91,000.
These cars are starting to get some years on them and it takes a devoted person to keep them up and running.
I hope I helped.

 

If I understand this right (?) if the engine cooling fan is not running when it's needed, it's either the 50 amp fuse or the fan control module. Are these two located in the same place or different?

Jim

 

What I can tell on page 7-37 in the service manual for the FCM the engine fuse block and the FCM are in two separate places. Also if you have an SRT-6 the FCM is in an different place than a N/A. The engine fuse block housing is located near the ECU housing near the battery next to the fill tube for the wiper fluid. Hope this helps. Please read post #4 from pizza guy on the communications from the FCM and the ECU.

 

The fan itself could be defective also. You are supposed to jumper the wires to the battery to check it. The easiest to check first is the 50 amp fuse box near the battery but you need to disconnect the battery first if the fuse does not visibly look broken if that makes sense. Otherwise disconnect battery, disconnect fuse and take a close look at it.

 

I had low coolant lite come on a few time while driving, when checked, found coolant was low. Refilled coolant tank, but light came on again not long after. Found that there was an old repair (b4 me) to the top radiator hose. Simple - replace hose, refill, all set. But the part shown has an extra hose which returns to the coolant tank. When I checked my car, it lacks this hose, altho there is what appears to be a factory setup which routes along the top of the radiator back to the tank. Am I somehow looking at the wrong part, or should I just buy the hose recommended and cut and plug the extra hose??

Thanks in advance for your help!
Crow13

 

There is no aftermarket hoses available for the top radiator hose. One part goes to the expansion tank and the other to the side of the radiator and another side to the engine if I am not mistaken. No part of the hose should be plugged at all.

 

Crow, is that repair you have located where that smaller hose goes over to the overflow tank? A second question, that hose going from your overflow tank (the second hose), is it connected to anything? The three part hose (connections) shown IS the correct hose for the car. The two large hoses goes from radiator to engine. The smaller hose routes around to the overflow tank bottom from where that connection is closest to the top of the radiator. Hope this clarifies.


.