AC is intermittent
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Junior Member
Joined: Jan 2013
Posts: 54
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AC is intermittent
I have a weird problem...
When I get in the car in the mornings and at lunch time the AC kicks on
Right after I start the car,
When I get in it after work and start the car the AC does not come on.
I also notice in 2 occasions the AC kicking on after running over a bump.
Could it be a relay or loose connection somewhere?
Can a relay or switch not make contact when sitting in heat all day?
Let me know your thoughts!!
TIA
G'
When I get in the car in the mornings and at lunch time the AC kicks on
Right after I start the car,
When I get in it after work and start the car the AC does not come on.
I also notice in 2 occasions the AC kicking on after running over a bump.
Could it be a relay or loose connection somewhere?
Can a relay or switch not make contact when sitting in heat all day?
Let me know your thoughts!!
TIA
G'
Senior Member
Joined: Oct 2011
Posts: 399
Likes: 14
From: Chicago, Illinois
2008 S63
I'm having the same problem. I went so far as to remove the blower motor clean and lubricate. Still have the same problem. I noticed before it would only happen on rainy days. Now it happens all the time. If it's not the motor itself then I think there are another few components related. There is a blower motor resistor somewhere and there is a small square shaped device inside of the blower motor compartment that might be the culprit. Let me know if you figure anything out. I'm trying to avoid the stealership.
Super Member
Joined: Oct 2007
Posts: 643
Likes: 51
From: Southern California
2007 CL550
The A/C system is extremely complex. Take a look at the following information on the W220 A/C. The W221 system is probably even more complex. Click on the following -> https://mbworld.org/forums/6010836-post3.html Once you look at the pdf file at the link you will see that your problem may require someone with a lot of expertise in Mercedes A/C repair. If you are paying by the hour, the bill can run up fast for someone lacking the experience. I assume there is a similar W221 hidden diagnostic menu, but who knows how to access it?
Last edited by steveb9771; Aug 20, 2014 at 12:15 AM.
Member
Joined: Apr 2008
Posts: 131
Likes: 0
From: DFW
S550
It is probably your blower and or your relay. If you want to DIY, just unscrew it underneath the passenger side dash. I believe it is about 7 screws: 2 for the panel and then 5 for the blower housing. It should all come out in the pan and unhook the relay wiring. You'll definitely notice a lot of dirt / grime from excess water in the pan and also the blower coil will look nasty. In my case, I wanted to see if I could revive the blower before I bought a new one so I cleaned it the best I could. I also took a can of compressed air (stuff you use for your keyboard) and blew all the dirt and grime out of the blower coils. I basically took the can and out it right up to the center of the cool and blasted it with air. If your blower looks dirty on the outside, just wait until you do this. Mine exploded in dirt everywhere. I would suggest doing this outside when you hit it with the compressed air can. I cleaned that and the relay the best I could and reinstalled as that seemed to do the trick for me. I hope that helps since I know this is a common problem for a lot of s550.
Senior Member
Joined: Oct 2011
Posts: 399
Likes: 14
From: Chicago, Illinois
2008 S63
Blower motor regulator is the small plastic/metal box like device that sits next to the blow motor itself. Which could be a possible culprit. Now where is the blower motor fan control module located?
Last edited by Zerocarpileup; Aug 20, 2014 at 07:55 AM.
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223.168 & 213.012 & 906.633 & 214.005
Intermittent blower operation, sometimes the blower even runs on its own, is quite a common blower motor regulator issue on many other MB models.
Control unit location in the picture.
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Senior Member
Joined: Oct 2011
Posts: 399
Likes: 14
From: Chicago, Illinois
2008 S63
Which one of these 3 components would be more affected by a sudden impact or jarring? I would imagine the actual motor itself. I ask because as soon as I hit a hard enough bump the damn thing turns on. Never thought id be actually LOOKING for potholes to hit. Womp.
Member
Joined: Apr 2008
Posts: 131
Likes: 0
From: DFW
S550
Yup that worked for me. I made sure i used an air to clean out the coil looking thing. I was definitely surprised how much dust and dirt got in there. It'll save you a couple hundred at least.
Super Member
Joined: Jul 2007
Posts: 636
Likes: 3
From: Orange County, Ca
C350
Hi All, I seem to have a similar problem but mine is simply when turning on my W221. Then the AC may or may not come on during the drive, but usually it will not. If it does, it takes around 30 minutes which is just unbearable inthe Socal sun.
Can anyone please provide instructions and DIY pics? The one pic was a bit confusing to me. Are these parts in the glove box or under the glove box?
Thanks in advance! I've taken my car to MB Anaheim and have contacted MB-USA but they havent found the problem and are pretty useless. Now I'm out of warranty.
Can anyone please provide instructions and DIY pics? The one pic was a bit confusing to me. Are these parts in the glove box or under the glove box?
Thanks in advance! I've taken my car to MB Anaheim and have contacted MB-USA but they havent found the problem and are pretty useless. Now I'm out of warranty.
Member
Joined: May 2007
Posts: 95
Likes: 17
S550 4MATIC
Hi All, I seem to have a similar problem but mine is simply when turning on my W221. Then the AC may or may not come on during the drive, but usually it will not. If it does, it takes around 30 minutes which is just unbearable inthe Socal sun.
Can anyone please provide instructions and DIY pics? The one pic was a bit confusing to me. Are these parts in the glove box or under the glove box?
Thanks in advance! I've taken my car to MB Anaheim and have contacted MB-USA but they havent found the problem and are pretty useless. Now I'm out of warranty.
Can anyone please provide instructions and DIY pics? The one pic was a bit confusing to me. Are these parts in the glove box or under the glove box?
Thanks in advance! I've taken my car to MB Anaheim and have contacted MB-USA but they havent found the problem and are pretty useless. Now I'm out of warranty.
Super Member
Joined: Jul 2007
Posts: 636
Likes: 3
From: Orange County, Ca
C350
I believe, there is no air at all, so maybe that means its the blower motor? I think there has been a couple of times when the problem happened and I turned the fan to setting 7 and it kicked on again at full blast, so maybe thats the regulator?
Junior Member
Joined: Aug 2017
Posts: 50
Likes: 8
From: Houston, TX
W221
Junior Member
Joined: Aug 2017
Posts: 50
Likes: 8
From: Houston, TX
W221
Oh, this 'ol thing! I hope this is not the problem. My AC fan comes on and off intermittently. Since it does come on most of the times, I don't think its the fuse. That leaves me with the actual blower (2218202714) or the blower regulator (2218706758). My logic tells me that since the fan blows decent amount of air when it does come on, its not the blower either. That leaves me with the regulator. The regulator may be giving intermittent signals to the blower to come on. Does my logic sound correct? If so, is there a way to test the regulator before I order new one?
Member
Joined: Mar 2018
Posts: 187
Likes: 34
From: Henderson, NV
2008 CL550
I realize this is an old thread but I encountered a similar issue with my 2008 S65. I followed all the recommendations here but none worked. Finally took it to the dealership and had them diagnose the issue. Turns out the front SAM was bad and not sending voltage to the blower motor. $1,000 later I have a working AC again.
