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2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
WHY is this fan running?
Today, I drove to the grocery store, 20 minutes in and out. Then to Wally World for 2 boxes of BC Powder.
I arrived back home at 2.30pm and parked in the garage, but left the garage door open. I went out at 4.00pm to close the garage door (now 4.30).
I heard a fan running under the hood. What the he!!? Watch the video below. So, I checked the voltage and it was at 12.06. Is THIS my battery problem I described in my other post ?!??
I removed the battery cover and see this fan running - not sure what that fan is for.
I sat in the GLK and turned the key to ON, and the fan stopped, then I turned the key off, got out and shut the door ... moments later, that fan started running at full speed !!
So I turned the key ON, then Off, but I did NOT shut the driver's door completely, only pushed it to the 1st "click".
Fan did NOT turn on.
Problem I was worried about is that the overhead lights were still lit (dash lights did turn off). So I waited a couple minutes, then used my thumb to push the driver's door completely closed.
No fan at this moment (4.40pm). I also put the trickle charger on it. Thankfully I left the garage door open and went back out, or that fan might have run all night long until battery dead.
What in the he!! is going on? Why was that fan running for 1 1/2 hours? Notice in the video I proved the fan is running when I stuck my fingers in there
I think that’s the climate control - vent AC Heat fan . Is air coming out the vents or floor? Just a guess a bad control module . Yes that will kill a battery
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by calder-cay
Is THIS my battery problem I described in my other post ?!??
I think this is something new, because I have never heard this fan previously. I've been out in the garage numerous times throughout the day, every day, to check the battery. This is some oddball prob that showed up today.
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by Mmr1
I think that’s the climate control - vent AC Heat fan . Is air coming out the vents or floor? Just a guess a bad control module . Yes that will kill a battery
Climate control fan (?).
The inside fan is set on Level 2 (2 lights lit on button). I had the inside air on (it's always on) to the grocery and Walmart. But on the way home, I fired up the A/C and bumped the fan speed to 3 ... but turned A/C Off (as usual) and dropped fan speed to 2 as I pulled into driveway.
I find it odd that fan is directly associated with battery top cover. (it has a dedicated tunnel). I just checked (7pm) and it's not running
Last edited by calder-cay; Feb 28, 2025 at 08:45 PM.
My Volvo XC90 used to do that to purge moisture from the AC evaporator. It's informally called "afterblow". Never heard of it in a Benz, although I understand it might be a good idea in the X166 cars... (Smelly climate control boxes.)
From my understanding the fan kicks on to dry out the vents to prevent mold/odor.
That blower/motor is where the fresh air enters the car. The plastic box installed above the battery directs air from in front of the windshield into it then into the car. so dirty air from the engine bay does not enter.
@calder-cay Yes, that’s the climate control (hvac) fan. And yes it’s supposed to run as described by @TimC300 . Every MB I have owned has done that in some form. But no, it’s not supposed to run on high. It’s supposed to run on the lowest speed. If it’s running on high for 30 minutes that will be a large current draw from the battery and could be contributing to the low voltage you have been experiencing.
Serendipity?
Do you still have the old battery ? 12.06v isn’t good . Is it possible 12.06 is causing electronics to be erratic ? I didn’t think what others mentioned about the vent system automatically running the fan to dry it. Voltage can cause weird things to happen . Have you ever cleaned the AC coil and vents using a spray up the AC condensate drain ? I ask because you must be in a warm humid climate to be running the AC in February. There must be a moisture sensor inside the vents somewhere. Is it possible spraying a cleaner up the AC condensate drain could clean the sensor ? Is it real humid where you are ?
I cleaned my AC coil and ducts with AC coil spray by spraying the liqued up the AC condensate drain, my ducts smelled of mold which is a common Glk issue, ( wasn’t there a recall or court order for this ?) . I also got myself sick for days by driving the vehicle right after doing it. All the mold and chemicals filled the cabin . Be careful and let vent system air out as they recommend. I think at least 30 minutes without being in the vehicle with windows open and vent fan on high. Hot air logically would speed up the drying process.
Today, I drove to the grocery store, 20 minutes in and out. Then to Wally World for 2 boxes of BC Powder.
I arrived back home at 2.30pm and parked in the garage, but left the garage door open. I went out at 4.00pm to close the garage door (now 4.30).
I heard a fan running under the hood. What the he!!? Watch the video below. So, I checked the voltage and it was at 12.06. Is THIS my battery problem I described in my other post ?!??
I removed the battery cover and see this fan running - not sure what that fan is for.
I sat in the GLK and turned the key to ON, and the fan stopped, then I turned the key off, got out and shut the door ... moments later, that fan started running at full speed !!
So I turned the key ON, then Off, but I did NOT shut the driver's door completely, only pushed it to the 1st "click".
Fan did NOT turn on.
Problem I was worried about is that the overhead lights were still lit (dash lights did turn off). So I waited a couple minutes, then used my thumb to push the driver's door completely closed.
No fan at this moment (4.40pm). I also put the trickle charger on it. Thankfully I left the garage door open and went back out, or that fan might have run all night long until battery dead.
What in the he!! is going on? Why was that fan running for 1 1/2 hours? Notice in the video I proved the fan is running when I stuck my fingers in there
As other forum members said, it is the fan that gathers air from the outside, goes through that filter you see in the engine compartment then a second filter called activated charcoal air filter inside the cabin to deliver fresh air to you. As others mentioned, it is supposed to run, to optimize the air and prevent mold and mildew to form like the newer MB models. Newer MB models have a feature called residual heating in certain markets that does the same thing with a press of a button.
That got me curios. There was a lawsuit on mold and mildew build up from newer models, I wonder if it is because they disabled this fan from running after shutting down for an hour because of battery drain issues, leading to residual moisture? It is not documented anywhere.
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by Mmr1
Do you still have the old battery ? 12.06v isn’t good
...
I ask because you must be in a warm humid climate to be running the AC in February.
@Mmr1 ... I still have the original battery - have not bought a new one yet.
That 12.06v is the reading I got AFTER that fan quit running. That battery averages a reading of 12.48 every day about 10am. So that 12.06v was the result of that fan running.
And yea, it's hot down here in south east Texas, and we have high humidity levels. Yesterday, it was 82°F with 40% humidity. Right now (10.30am) it's 71°F and 50% humidity. It's not unusual to have 100+%f temps in mid summer with 90% humidity.
Originally Posted by Odd Piggy
@calder-cay Yes, that’s the climate control (hvac) fan. And yes it’s supposed to run as described by @TimC300 . Every MB I have owned has done that in some form. But no, it’s not supposed to run on high. It’s supposed to run on the lowest speed. If it’s running on high for 30 minutes that will be a large current draw from the battery and could be contributing to the low voltage you have been experiencing.
@Odd Piggy ... it's odd, after all these years with the MB, I've NEVER noticed that fan running after a drive. I placed a spare Wyze security camera in the garage, pointing at the GLK, and have it set to send a notification to my phone if it detects a sound.
So, Fri was the last GLK drive. I'm tempted to go for a 30 minute drive later today, then park it and see if that fan fires up again.
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by TimC300
From my understanding the fan kicks on to dry out the vents to prevent mold/odor.
...
Can find it in the manual under Heating and Air Conditioning > Description and Operation > Regulation of Automatic Air Conditioning, Function > Part 1
...
Its the Manual for the 2010 GLK350.
...
Looks like after the car is switched OFF the fan kicks in 1hr later for approx 30 minutes.
Hi @TimC300 ... I appreciate your detailed reply and reference to the manual !!
I have a paper version of the manual in the glove box, and have a PDF version on my laptop, so will see if my manual has this section.
@Odd Piggy ... it's odd, after all these years with the MB, I've NEVER noticed that fan running after a drive. I placed a spare Wyze security camera in the garage, pointing at the GLK, and have it set to send a notification to my phone if it detects a sound.
So, Fri was the last GLK drive. I'm tempted to go for a 30 minute drive later today, then park it and see if that fan fires up again.
It's likey running on slow speed and the microphone would probably have to be unnecessarily sensitive to pick up something like that.
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by MBKLUE
It's likey running on slow speed
Flipping TV channels to the NASCAR race in progress... they are actually on a track that has left and RIGHT hand turns?? Hope that doesn't confuse them
@MBKLUE ... nope - if you go back to the video, that fan is running at top speed - it was obvious in person.
...
Okay, I drove 45 minutes today, then parked and checked every 10-15 minutes. It's now been 1 1/2 hours. That fan NEVER turned on.
However, today, I mistakenly forgot to turn the a/c on the last 15 minutes of the drive as I did on Fri - maybe that makes a difference. So tomorrow, on the grocery errand, I will fire up the a/c back home.
Guess what I discovered (?) ... there is a "door" that closes that fan area. I witnessed it today after the first 5 minutes after shutdown. Then it immediately opened back up after 10 seconds. I will show it to tomorrow. it's easily closed with a finger.
2006 Alfa Romeo Brera, 2010 GLK350, 2018 BMW 640i GT, 1997 Subaru SVX, 2012 Moto Guzzi Norge GT8V
I always turn the AC off a few minutes before parking the car. It dries things out. I've never had the fan run by itself even at 90F and high humidity.
The link I posted is for the entire repair manual, I think it may be referred to as the WIS or workshop manual. https://charm.li/Mercedes%20Benz/
It only has 1982-2013 Models though, and the 12-13 manuals dont seem all that complete. But for my 2010 it looks like everything is there.
When I thought I had an issue with my battery and the car electronics doing things when the car was off i bought the bluetooth battery monitor Ancel BM200. Its a neat little device, just connect it to the battery and you can see the voltage off the app. I dont think its accurate for showing the battery state of health or state of charge but for showing real time voltage its good. I would drive around and see how the alternator was charging. You can easily check the battery voltage from the dash but only when you are in the car, with the Ancel monitor you can see the voltage while the car is off and it shows it on a graph. When I had it hooked up over a few days I noticed the battery voltage would drop around the same time in the morning, which seemed to coincide with the sun coming up. I didnt dig into it any further but leads me to think the car was turning something on to remove moisture in the car? Im purely speculating.
I also noticed id go out and unlock the car, open the door and pop the hood, go into the engine bay to do some work and id hear all sorts of things turning on and off under there. When I was working at the battery I would remove that plastic box above the battery and the door/flap at the blower would close and open on its own. the car must be performing its checks.
Talking about mold I was looking thru the manual and came across the procedure to clean the evaporator.
Flipping TV channels to the NASCAR race in progress... they are actually on a track that has left and RIGHT hand turns?? Hope that doesn't confuse them
@MBKLUE ... nope - if you go back to the video, that fan is running at top speed - it was obvious in person.
...
Okay, I drove 45 minutes today, then parked and checked every 10-15 minutes. It's now been 1 1/2 hours. That fan NEVER turned on.
However, today, I mistakenly forgot to turn the a/c on the last 15 minutes of the drive as I did on Fri - maybe that makes a difference. So tomorrow, on the grocery errand, I will fire up the a/c back home.
Guess what I discovered (?) ... there is a "door" that closes that fan area. I witnessed it today after the first 5 minutes after shutdown. Then it immediately opened back up after 10 seconds. I will show it to tomorrow. it's easily closed with a finger.
Yes, there is, it is meant to close when you are in recirculation mode.
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
Originally Posted by W205C43PFL
Yes, there is, it is meant to close when you are in recirculation mode.
We have never had recirculation mode enabled. So why did that door close, then open seconds later.
That sequence happened after the car shutdown ... then a couple minutes later, I got out of the car, opened the hood , then removed the cover (an obvious 2-3 minutes) ... and about 20 seconds later, I saw that door close... then seconds later, it opened back up. What's the point of closing, then opening seconds later AFTER the car is shut down after a few minutes (?)
We have never had recirculation mode enabled. So why did that door close, then open seconds later.
That sequence happened after the car shutdown ... then a couple minutes later, I got out of the car, opened the hood , then removed the cover (an obvious 2-3 minutes) ... and about 20 seconds later, I saw that door close... then seconds later, it opened back up. What's the point of closing, then opening seconds later AFTER the car is shut down after a few minutes (?)
I do know that fresh air/recirculation door will close then open on mine after I unlock the car and open the door. I hadnt even put the key in the ignition when it happened. I figure its the car going thru its function checks. I believe it also happened after replacing the battery, a minute or two after connecting the new battery it did a function check. I also hear noises from the front sam and I think noises from the throttle body.
Maybe it has something to do with the front door opening/closing? The more I read the more im amazed at how these things all work.
Theres a motor that moves that door open and closed. fresh air comes in from the front of the windshield down past the plastic trim, goes through the box above the battery then to the blower. To recirculate the air that door closes to the outside and air is then sucked in from the dash board.
Heres how the air flows, shown with the box above the battery removed.
Fresh air comes in at blue arrow above, recirculated air in red arrow.
I do know that fresh air/recirculation door will close then open on mine after I unlock the car and open the door. I hadnt even put the key in the ignition when it happened. I figure its the car going thru its function checks. I believe it also happened after replacing the battery, a minute or two after connecting the new battery it did a function check. I also hear noises from the front sam and I think noises from the throttle body.
Maybe it has something to do with the front door opening/closing? The more I read the more im amazed at how these things all work.
Theres a motor that moves that door open and closed. fresh air comes in from the front of the windshield down past the plastic trim, goes through the box above the battery then to the blower. To recirculate the air that door closes to the outside and air is then sucked in from the dash board.
Heres how the air flows, shown with the box above the battery removed.
Fresh air comes in at blue arrow above, recirculated air in red arrow.
I had no idea the cabin air filter was in a different location on the pre-face lift model. I'll take it! The filter location/replacement on the later GLK is the most awkward, annoying, frustrating, dumb setup I've ever encountered on a car.
You’re supposed to filter all incoming air , right? I wonder if the filter in the photo - pre 13 would fit on a facelift Glk . Now I’m sucking in everything. I have not done the interior filter myself but my friend who does mine did say the interior filter was a B
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