When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
2010 S450 4matic. The car is new to me. It was my Dad’s car. He can’t drive anymore for health reasons 😢. The car sat in the carport for about 8-10 months. Trying to sort it out so will be posting multiple threads. Thanks in advance for the help. I am grateful.
Radiator fans starts full blast as soon as the engine is started. Stays on even after engine is shut off. Will run indefinitely. The only way to shut it off is to unplug it.
2010 S450 4matic. The car is new to me. It was my Dad’s car. He can’t drive anymore for health reasons 😢. The car sat in the carport for about 8-10 months. Trying to sort it out so will be posting multiple threads. Thanks in advance for the help. I am grateful.
Radiator fans starts full blast as soon as the engine is started. Stays on even after engine is shut off. Will run indefinitely. The only way to shut it off is to unplug it.
Fan has 04 wires:two big one connect to battery, the other small one is 12V powered when you turn the car ON, the last one is control signal connected to pin 43 of the ECU (small ECU harness) and fan will run max speed if control signal is lost.
12V main power and connected to battery 12v power when car is on Pin 43 is fan control signal from ECU You need to check conntinuty between pin 43 and the last terminal of fan
The fan runs if it doesn't receive a signal from the ECU.
It can therefore be SAM, ECU or Fan controller.
It will also run if there is a communication issue with another ECU.
e.g. gearbox ECU disconnected will cause fan to run on full blast. I would assume that there is an intermittent communication issue with something not critical to driving.
A malfunction in my air conditioning compressor which occurs after its been running for about 30 minutes where the head pressure gets high and sends a signal to the fan to turn on high to try to cool it down. I don't really loose cold air until it gets to a certain temperature
If the ECU gets implausible readings on engine temp it puts the cooling fan on max
If there are complaints with these vehicles that the electric radiator fan or auxiliary fan runs constantly, even when the ignition is switched off, one possible cause is moisture in the fuse box. Water penetration into the fuse and relay box gives rise to corrosion and therefore to contact problems on the electrical connections. In order to eliminate the fault, the fuse and relay box should be removed, and the electrical connection checked for corrosion. If possible, the connections should be cleaned. In the event of excessive corrosion, the fuse and relay box must be replaced
I vaguely remember something similar happening to my 2010 cl550 4matic. I believe I caused the radiator fan to get stuck on by clearing codes with the engine turned off. Have you done something similar recently?
I vaguely remember something similar happening to my 2010 cl550 4matic. I believe I caused the radiator fan to get stuck on by clearing codes with the engine turned off. Have you done something similar recently?
yes actually I have cleared codes recently…interesting.
you don’t happen to also remember what was the fix? 😄
yes actually I have cleared codes recently…interesting.
you don’t happen to also remember what was the fix? 😄
that’s kind of why I didn’t want to chime in, unfortunately I don’t exactly remember what the fix was...I think it was doing a rescan and clear of the codes with the engine running.
that’s kind of why I didn’t want to chime in, unfortunately I don’t exactly remember what the fix was...I think it was doing a rescan and clear of the codes with the engine running.
that’s kind of why I didn’t want to chime in, unfortunately I don’t exactly remember what the fix was...I think it was doing a rescan and clear of the codes with the engine running.
Gave it a try this afternoon. Used a random Optima scanner to clear all codes. SUCCESS!
never heard of or come across this as a result of running diagnostics - these first two reasons for the fan running, came from to very experienced merc experts in the UK
The fan runs if it doesn't receive a signal from the ECU.
It will also run if there is a communication issue with another ECU.
as they both say its can be comms issues on the car driving the Fan to run in safety first mode - it would suggest if you have ever got this from running diagnostics tools - then you should STOP using those tools - as they are not communicating correctly with the car - indeed it indicates they are attempting deeper level control (than just reading and clearing fault codes) and getting it wrong - this is a very dangerous situation as it could damage modules or software making the car undrivable, introduce errors an or make it unsafe by confusing or damaging safety systems
