miami1lt

All,

After shutting off our ML350, about 10 minutes later, there is a noise that sounds like an A/C fan coming from the driver side engine compartment. I can hear it through the little air ducts in the hood...it almost sounds like a fan (like if I had accessories on but I don't).

Then, when I open any door, it goes off...I don't know how long it stays on, as I haven't ever waited it out...but at least 5 minutes.

Thoughts?

It shouldn't be accessories, since I've cleared the car and removed the key. But not sure what is on that side of the engine bay that could turn a fan on, and why it would happen when the car is off. Thanks!

pharaoh

That could be the COMAND's fan running. Check if your lights are turned off and your key is out as well.

brentkhack

It is the A/C rest button that is on. I think it uses the engines heat to keep the inside warmer up to 30 mins or until the battery goes below a certain level.

miami1lt

Interesting...never heard of the A/C rest...

So, when you say inside, do you mean inside the engine bay, or inside of the car? Since I live in HI, inside the car wouldn't do anybody any favors, but...is it temperature drivin or simply something that just happens?
Very interesting stuff! Thanks.

gsrjc

hmm, i'll have to pay attention to this as i don't think i've heard this noise.

pharaoh

That is incorrect. The AC Rest will not turn by itself unless you turn it on after turning the car off.

brentkhack

I have had the A/C Rest button turned on while the vehicle is on. Then parked in my garage. A few mins later I went back in the garage and found the same fan running by the grilles in the hood. So I looked at the manual and it uses the residual heat in the engine bay to heat the inside of the vehicle.

ajSvat

The A/C rest feature only functions if you activate it.

Let’s say it’s very cold outside and you’ve just parked your vehicle to wait for a passenger to arrive. You turn off you vehicle and the interior slowly starts to get cold so instead of staring the motor to warm up you just push the A/C rest button and vola! You have heat.

ductman

My wife"s 2010 does the same thing, doesn't matter whether the heat or air is on or not, kind of strange if you ask me. Dealer claims it is" normal", something about drying the evaporator out, do not see any mention of this in the manual.

miami1lt

Exactly, somebody else notices it. My wife can run to the corner and back within 2 minutes, and it makes the noise. I always know because I go out in the garage 30 minutes after she gets back, and I hear the "vvvvvvvvvvvvvvvvvvvvvvv" of a generator fan. It is very interesting, and agree, it is nowhere in the manual or any tech notes I've seen. Thanks for confirming that is happening for me.

MB211

It is indeed normal. The blower fan runs for several minutes interm to dry out the evaporator. This reduces chance of a/c musty odor.....I believe MB term for it is "afterblow" or something to that extent. Also happens on other MB models.

jimmyp

My 2010 gl sometimes does the samething its the fan running

bdbML350

I have the same problem with our 2010 ML 350 Bluetec. Residual heat fan turns itself on after enginer is shut off and everyone exits the vehicle. Not sure how long it runs for, but might be as long as 30-45 minutes. Open the door and the fan turns off. Will let you know what my dealer says about this. Also have similar problem with radiator fan turning itself on after engine is turned off. MB says it is normal - but don't explain why or what circumstances cause it to occur. It's intermittent and not caused by over-heating. It's been plenty cold here at -5C and it still happens 1-2 times per month.

sosh

Wrong!! Does not use the residual heat in the engine bay. It does use the same heater core that it uses while running to provide heat UNTIL that cools off.

EnigmaAW

mb211 is right on the money. my glk does not have this function, so i get a pretty bad musty odor sometimes when i turn the a/c on. this is something MB started after my production date in 2008. several glk owners have the musty a/c problem.

miami1lt

Guys, sorry for the 3 year hiatus, but I'm back, with an ML63 now...use...2008. Anyway, I see mention of the muster odor from the A/C...well I can tell you this is an immediate problem. Has anybody found a way to reconcile this problem (we are thinking of using little febreeze plugs in every vent, but I hate to ruin the interior ambiance with a bunch of smell sticks). Appreciate any help.

BMW&Benz

so on your 08 ML63 you don't have an A/C Rest button? is that why you have the musty odor?

My 2010 does this **** a lot and I knew we were turning the A/C off and engine off only later to hear this sound.

Does anybody know how long it will run for? When I've gone out to the garage it turns off as soon as I open the door....but if I didn't do that how much longer would it run for? I'm concerned of battery drain issues.

bdbML350

this fan runs to remove/reduce condensation in the HVAC system and vents. when I mentioned this to our dealer back in 2010, even the service manager thought it was strange. his own demo unit did the same thing, so we he wheeled it into the service department to have it checked out. it seems like an awkward way to keep condensation from building up, but I don't think there's an easy way to disable it. you'll have to get used it running on it's own.

bdbML350

some more info....it seems to run for about 10-15 minutes, and will shut off as soon as a door is opened. as for battery drain, dealer says the system will shut itself off well before draining the battery.

blake.1

Hi, I have a SLK250 with the same problem. It shut off as soon as a door is opened, however, when I shut the door, it goes again. I took the car to the dealer's service centre but they couldn't locate the problem after the car in their workshop for a week. This problem comes and goes. For example, yesterday I came home, turned off the engine, pulled out the key, got out and closed the door, I put my hand over the little air duct in the hood but can't feel anything. My husband came home an hour later and told me that the fan is running again. We didn't know when it came on but we waited to see how long it took to go off. It took another half an hour. So my question is do you think this is also caused by the condensation? By the way, I live very near to my work, about 7mins drive, do you think the short distance driving creates more condensation to the air conditioning unit?

buckybr

blake.1 I have a 2013 250 SLK and a 2011 ML350 and both do the same thing.I am told by dealer it is normal.

blake.1

You have had your 2011 ML350 for a while now, so you never had any flat battery problem associated with it? That's a good sign.

mghomes

I'm having the same problem with my 2010 ML350. I took it to the dealer and they claim it's feature of the vehicle. Yet when I initially told my service tech. and left the vehicle with him (8days), the motor fan was changed because according to him and his mechanic, that was the problem. Drove it home and drove it back the next day for the same issue. Now they've had my vehicle for a week and the great news according to them is that it's a "FEATURE" of the ML350. "It's NORMAL" they say. I wish I could believe them.

mickeyb

Joining this thread late - not sure if I'm having the same issue.

The radiator fan on my '07 ML350 has been turning on and off almost constantly for the last few weeks, running so loudly that it sounds like a truck is driving alongside. Happens on short trips, long trips, in traffic, on the highway -- constantly. On, off, on, off, etc.

Took it to the dealer and they said it's "normal," and that I must not have noticed it before. Ah...no. It is not that I haven't noticed it before; it started doing it a couple of weeks ago.

Something is telling the fan to kick on, tho nothing indicates over-heating.

Any ideas or insight?

don.calo

Noticed fan under hood driver side running on 2010 ML350 4Matic after short runs in hot weather (AZ) also. Takes about 45 min to go off and no dead battery.
Have not experienced this with 09 ML but it is used for longer runs.