Hey guys, does any of yours vehicle’s radiator fan will go on for around 10 mins after turning the vehicle off? Oil temp, coolant temp etc all normal. The fan will on at high spend for about 5 mins, and the at relatively low speed. Went to the dealer twice, they checked on computer, all codes are free from error. Driven the car a little bit over a year, never happened before, just recently. Every time after driving for a while and temps go up to the normal and turn off the car, the fan kicks in. Really annoying. Please help. Thank you for your reading!
Radiator fan running for about 10 mins at high speed after turning off
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I have not noticed my fan running after shut down. I haven't worked as a dealer mechanic for many years. So I could be suggesting the wrong discovery path. But, based on my non-MB experience, electric cooling fans are typically triggered by a temperature sensor that typically screw into the radiator. I may be remembering incorrectly, but I believe the fan goes on when the temperature sensor completes a circuit by establishing a ground when it senses the coolant temperature reaches a certain point. So, based on this logic, it seems likely that your sensor is completing the circuit by establishing that ground when the coolant is lower than the normal trigger temperature. If I am correct, and I could be wrong, the malfunctioning sensor will not show up on the dealer's computer. I am not aware of any way to test the sensor. So, the only way to either verify my diagnosis, or show I am incorrect, is to replace the temperature sensor. This may cost a few Dollars to buy the sensor. But I am not aware of any other way to test my theory. Just an idea...
Hi Rob, thank you so much for your reply. Can I double confirm the sensor you are referring to, is that a coolant temperature sensor that may have malfunction? I’m sorry that I’m not very familiar with the mechanic part, may I ask what is the specific term for the sensor based on your experience?
I visited two dealers and both of them told me everything is alright, that’s really annoying because the fan noise is very noticeable especially when I parked the vehicle in a underground parking lot. Again, thank you so much for your clarification!
I would call it a cooling fan switch. I say that because, although I may have the MB terminology wrong, our cars also have a coolant temperature sensor. The sensor feeds the coolant temperature gauge. (In some cars the sensor may feed an idiot light and not a gauge.) The fan switch is a separate component. Using the incorrect name may lead to somebody like a service manager or a mechanic respond to you with an incorrect answer. The cooling fan switch is in the circuit that powers the cooling fan. If you want more information just google "cooling fan switch". When you do it responds with pictures of various switches from Autozone. They all look a little different because they are likely for different cars. But you can see they all have male threaded ends that screw into radiators, and connections for wires. Our cars likely have a switch that looks similar. When you google it the results include a demonstration of using an ohmmeter to test the switch. Ohmmeters measure electrical resistance. I believe the fan switch should normally have high resistance until it senses coolant temperature raised to a certain temperature. When the coolant reaches normal operating temperature the resistance should drop to a lower point which allows the DC current to flow through the switch and the fan to come on. BTW, you can get a pocket dial thermometer from Amazon for $8.69. I haven't used mine for years. But you can use it by inserting it in the coolant when the fan is on or off to tell you the coolant temperature when your fan comes on. It will likely tell you the fan is coming on at a lower than normal temperature.
That's really helpful! Thank you so much of being so patient and I will definitely let my mechanic take a look into it. Hopefully I could have this issue resolved soon. Thank you so much!
You are very welcome. Keep us informed so we know how the issue is resolved.
Can you provide the coolant temp when this happens? Not how many bars real temp. There is a screen it displays oil and coolant temp.
I can tell in my car it never goes above 93C
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Do know that in hot climates that cars that have aircon than the interior fan will keep operating for some time after the engine is switched off ..Reason is to bring the temperature back down to normal in the cabin..
Others may know more about this than me. So, please feel free to respond to this to agree or disagree. But I am skeptical about this AC fan theory. First of all, what is "normal" in this scenario? For example say it is 85 degrees F outside, and 68 degrees F inside the car. Is normal the exterior temperature? If the car is not running, which means the AC compressor is not rotating, how does running the fan alter the interior temperature? Also A/C systems often recirculate the interior air so the system is cooling the cooler interior air, not hot external air. So, if I am correct, how does recirculating interior air after AC compressor is shut down when engine is turned off alter interior air temperature? Am I misunderstanding anything?
Rob just saying how it works on my other car . Went for a run first time ever after i purchased it Returned home switched of the engine .Left the car and went indoors ..My patio doors were wide open it was a hot day.Then all of a sudden the fans started to roar .Went out lifted the hood , but the engine fans were stationary .The air was being drawn in through vents under the front screen .Nothing i could do to stop it ,but after a short time the fans stopped .i read all about this in my owners hand book ..said its normal .
That function is to dry evaporator to prevent musty odors.
Well whatever you say .
That makes sense to me. Thanks!
We are talking about HVAC blower for evaporator drying.
Radiator fan is driven by engine coolant temp, oil temp and refrigerant pressure. Reading codes is not the method.
Need to look at actual values. What if refrigerant pressure sensor is stuck high?
I am not an expert on the way the technology works that supports the cooling system in our cars. So, please feel free to reply with answers. And feel free to correct me.
My terminology may be different than others. This may be because I have not worked as a mechanic for many years. I have a few questions/comments about the explanation above.
Think about the cooling system systemically. It has multiple components including radiator, water pump, thermostat, heater core, radiator cooling fan, coolant temperature sensor/switch, and hoses and/or plumbing. Under normal running conditions the fan turns on after the thermostat opens and coolant is being pumped through the entire cooling system. In simple terms hot coolant is pumped into the radiator, it is cooled by the air flowing through the radiator, and cooler coolant is pumped out of the radiator back into the engine. So, here are my questions:
Depends on the coolant temps. RO: At what coolant temperature does the fan turn on? If intercooler pump is dead and the turbo coolant is hot, RO: If the engine has been turned off, the coolant is not circulating. So, what is the purpose of cooling the coolant in the radiator if the coolant is not being circulated to the other components of the system? the radiator fan will keep running until it times out. RO: When does it time out? I ask because the ambient temperature varies based on factors like car location or season. As a result the coolant will take longer to cool in summer than it does in winter. Does the time the fan runs after shutoff vary based on factors like ambient temperature?
I also wonder how a cooling fan that may be designed to turn on after the engine has been turned off may affect mechanics. Is it possible for fan to turn on while car is turned off and it is being serviced or checked?
Sorry for the long winded response.
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG. 2011 BMW 335d
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Depends on the car, but usually around 105c if engine coolant, lower if turbo coolant circuit. Or if the refrigerant pressure is too high.
Hotspots. Heatsoak can and will damage the engine, particularly turbo's if you shut off the car immediately after running it hard. Coolant is definitely being circulated, most MB came with auxiliary pumps, the pump sometimes keeps running after the shutdown depending on situation.
Location or season is irrelevant. Hot is hot. Hot, fan runs. Temp comes below a threshold, fan stops.
Time out means the timer runs out and the fan MUST shutdown to prevent battery drain, irrespective if coolant temp hasn't gone down or not. Usually 10 mins, no more.
Irrelevant. When the delta between the coolant and ambient temp is over 50C, it will cool down. What does the car care if the outside temp is 45c? Coolant temp is 95 to 100C. The delta is big enough to allow for ambient temperature exchange. Yes, it's true that in winter the coolant will cool faster due to bigger delta, but at summer time it'll still cool down just fine. Otherwise all those cars in Sahara desert or Death Valley would've gone up in a ball of fire by now.
If you put a bottle of water in the fridge so it is at 10C and then put it outside in room temp of 22C, it will warm up and come to equilibrium temp. Delta is only 12C, but that is enough. The bigger the delta and the type of material used to process the osmosis of the temperature difference will affect how quickly (or slowly) the product reaches equilibrium with ambient temp. Think hot tea in insulated travel mug vs hot tea in an all aluminum cup. Which one will stay hot for longer?
No. Either the target coolant temp is reached after running the aux pump and fan, or fan times out. One or another.
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Bumping this. Took my car to the dealer but they insist that this is typical behavior for all GLC43 and GLC63’s which have large engines to cool. This is extremely frustrating problem for what is essentially a 1 year old car - can anyone with an AMG GLC tell me if the radiator fan kicks in when the car is shutdown on almost every trip?!?
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