mefferso

Just wanted to share my DIY experience. All in all, not to bad of job. Half a day if you take your time. My symptoms started with intermittent lack of cooling on the driver's side. It eventually completely quit cooling. Diagnosis from a local shop determined that I needed a new a/c compressor. Here's a list of the parts I bought:

A/C compressor:

Drier:


Orings:


oring removal tools:

http://www.homedepot.com/p/Husky-Pre...+%284-Piece%29

That compressor was a perfect fit in every way. It was pre-filled with some oil, but not enough. You'll need to empty out what it comes with, then add additional oil to get to the 110ml you need and re-fill. Don't forget to put the shipping cap back on it while installing so oil doesn't drip out.

I wouldn't buy that drier. The mounting tab placement and angles SUCKED. I had to do lots of bending and force it to fit. Therefore, I recommend trying a different brand.

Now, for the actual removal of the compressor and drier. You'll need to remove the engine plastic shield/skid plate first to be able to access the compressor from underneath. Next, to access the drier, the whole front bumper cover has to come off. Start with removing outer side of the front tire fender wells. There are 3 rivots that you'll need to remove to do that. For those rivets, use a small flathead screwdriver to pry up and out the center shaft first, then the outer flare will pull right out. Once you pull the outside fender well out, you'll have access to the T25 screw holding the top of the bumper to the fender. Remove that screw. Looking further inside, you'll see a 10mm bolt holding what looks like a wheel with teeth. Its used to hold and alight the bumper. Loosen but dont remove that bolt. Next you need to removed the 10mm bolt that holds a tab on the top of the bumper and the inner part of the both headlights. Once you've done that on both sides, remove the rivets that hold the grill in place and remove it. Next, grab friend/wife/child/randompersonwalkingdownthestreet to help you pull the front bumper cover off. Its takes "some force" but not a lot. BE SURE TO GO SLOW. I say that because there are 2 electrical plugs that you need to disconnect from the front bumper cover for complete removal.

Now you're at the point for removal of the a/c compressor and drier. The drier is easy, just the T25 screw holding down the in/out piping and 2-10mm bolts holding down the drier itself. I put an ounce of PAG46 oil inside my new drier before installing. As mentioned above, the crappy tabs on the one I bought made it a pain. Be sure to install 2 new orings on the in/out pipes. I lubricated them with PAG46 before installing them. Next, move on to the compressor. First loosen the serpentine belt. I used a long pull bar with a 17mm socket on the bolt head thats on the belt tensioner. Next loosen the high and low pressure pipes connected to the compressor. The compressor you buy will have the same bolts on it. So use that to figure out what size allen wrench you need. It took some wiggling and light tapping with a screw driver and hammer to get the high side loose. Push them out of the way to get better access to the electrical connection on the top of the compressor. Be very careful here as well. It will be snug and you dont want to break the locking latch. Once disconnected, I taped the connector up and out of the way. All you have left now are the 3 star headed bolts. You'll need a metric set of e-sockets. Be ready for it when you take that last bolt loose b/c its got a little weight to it. Finally, wiggle it out through the power steering hoses. Now change out the orings on the high and low pressure hoses. Once you have the new compressor filled properly and capped off, reinstall. I did it in this order: mounting bolts to the block, high/low side hoses re-attached, re-connect the electrical connector, serpentine belt. Everything else in reverse of the beginning starting with the bumper cover alignment. That took me awhile and couldn't have been done without the help of my handy wife.

That's it! Crank it up and bring it to your favorite place to pull a vacuum, check for leaks and re-fill with freon. I was quoted $1500 by my local shop if I had them buy the parts and do the entire job. Who knows how much the MB dealer would want. I bought the parts myself for ~$400 and paid my local guy $100 for the re-charge. I'll use half a day to save a $1000 every time.

Final words, don't be intimidated by this job. If you can do a break job, you can do this. Just take your time and pay attention to what bolts went where and what order you took things apart. Hopefully I didn't forget any steps. Please feel free to ask any questions and i'll do my best to help.

SFCabs

Great timing! I'm going to be doing this next week. I'm going to get the Hella drier and hopefully, that fits better.

I rented the vacuum pump and manifold gauges from Autozone so will do the refill on my own as well.

mefferso

Awesome! Hope it goes good for you.

SFCabs

I just started on this tonight and I'll be finishing it tomorrow.

Did you have any problems getting the o-ring off and on of the low-pressure hose? It's not easy to get to from the top or bottom. I guess I'll try to grab it with the pick.

Did you torque anything to spec? Although, I can't really get my torque wrench onto many of the bolts anyway.

mefferso

I found it easiest using the curled pick reaching up from the bottom. I got one side under the oring, twisted the pick, then grabbed the end of the pick with my thumb to keep the oring from sliding off. Putting the new one on was a little tougher just because it was slippery from lubricating it.

There was no way i could reach my torque wrench in there easily. I'd try to pay attention to how tight they are when you take it off and snug back on similarly. I just kept reminding myself that we're tightening onto aluminum and not cast iron or steel.

SFCabs

I'm having trouble getting the top A/C Compressor bolt off. The power steering metal pipe is lined up exactly on top of that bolt so my ratchet won't fit on top of the bolt. I'm trying to loosen and move the power steering line a few inches out of the way now. Was yours also in the way?

mefferso

Interesting, I don't remember mine being that close. I think i used a 3/8" pull-bar to break it loose. It's slightly shallower than the ratchet. Would a universal socket joint or swivel socket let you get in there at a different angle?

SFCabs

Some notes:

This appears to be the 3rd compressor for my GL in 9 years, which seems excessive. The original and previous owner always complained about AC issues, so hopefully, this compressor lasts for some time.

This took me way longer than the original poster. I blame my short fat arms and lack of visibility and access. It seemed I kept hitting some roadblock where I would need to go get something to help resolve it.

I had to loosen the power steering line coming out of the pump and rotate it a bit out of the way. Without moving it, there was no way to get a socket onto the top front bolt of the compressor.

You need a 12 point 17mm socket for the belt tensioner.

Getting the new compressor on and lined up took some time. You'll have no real visibility and you have to hold the compressor at an awkward angle while trying to get the first bolt into it.

My Denso compressor had ZERO oil in it when I got it. I tried rotating it in every direction and spinning it but nothing came out.

I filled the system with R-134a myself.

I rented the manifold and vacuum pump from Autozone. I pulled a vacuum for about an hour and waited another hour to make sure it held a vacuum.

The system takes 34 ounces of R-134a. I got 3 cans for $26 at Walmart. and used all of the first 2 cans and only 10 ounces of the last can. The cheapest place in my area charges $75+ for a refill.

R-134a bottles sold in California are self-sealing and need a DVA-1 adapter.

In the end, it seems everything is working properly and I'm getting 41-degree air coming out of the vents now. Thanks again to the original poster!

mefferso

No problem SFCabs, glad to help! Thanks for sharing your experience and additional info for others as well. You're definitely right about the lack of visibility for some things. A nice pair of clear glasses saved my eyes from crap falling too.

4loops

Thanks for the excellent writeup mefferso, I will be replacing my failed compressor and dryer & condenser, as the compressor was diagnosed as failed. I had the same symptoms starting around last summer: ac would come and go, then seem to ironically only work when it's not blistering hot, then nothing. Fortunately the nothing was throughout the winter, but we'll need it again here very soon.

A question for you and others watching this thread: have you heard any warnings against using a non-Denso brand? I've learned Denso is the OEM brand used originally and should work fine, but I have found others can be cheaper. BUT, I think I'm remembering from my research on this last summer that some other brands don't respond to the PWM (or frequency?) signal properly, and won't work. Have you heard anything like this? I hope I'm not seeding doubt or misinformation here but I genuinely think I ran across a thread saying this. Any thoughts?
Thanks!

BenzBallin

is this a Common issue with Gl class ? do these compressors usually go bad on these cars ?

S-Vibes

You can use other than DENSO, but you need to add a 10 cent diode to make it work.
https://mbworld.org/forums/gl-class-...de-9006-a.html
https://mbworld.org/forums/gl-class-...ompressor.html

Tommyworx1

I you seem to have a good understanding about The GL450..I have a 2007 GL450 that I am trying to locate the AC fuse or relay fuse.
I'm pretty sure its the compressor thats bad...but would like to check a fuse if there is one. I haven't been able to find much information about the AC fuse or relay locations.

S-Vibes

http://www.mercedesmedic.com/gl-fuse-chart-x164/

you're welcome

Tommyworx1

GL-Class Fuse Box in the engine bay.

I don't see AC compressor fuse?

is it the same as the power steering fuse?

Its my 1st Mercedes purchase ...thanks for the help.

Fuse Function Ampere 100 Wiper 30 101 Purge Control,
Oxygen Sensor Upstream 15 102 Transmission Oil Pump 10 103 Engine Control Unit 25 104 – 15 105 Connector, ME Control Unit 15 106 Not used – 107 Air Pump 40 108 Air Compress for Air Suspension 40 109 Electronic Stability Control ESP 25 110 Antitheft Alarm System, Siren 10 111 Direct Select 30 112 Headlights 7.5 113 Horn 15 114 Front SAM N10 5 115 ESP 5 116 VGS 7.5 117 Distronic DTR 7.5 118 Engine 5 119 Control Unit 5 120 Engine 10 121 Heater 20 122 Engine Starter 25 123 Fuel Filter 20 124 Power Steering 7.5 125 Not used –

4loops

Sorry for the late reply..

Looks like the compressor would be fuse 7.

My reasoning is,

• According to the link S-Vibes sent: http://www.mercedesmedic.com/gl-fuse-chart-x164/, Fuse 12 is "Air Conditioner Controls"
• According to this page I found (http://ww2.justanswer.com/uploads/eu...assignment.pdf), Fuse 12 is "AAC [KLA] control and operating unit (N22)".
• So, Mercedes Benz calls "A/C", or "Air-Conditioning": "AAC". A little more research on this shows that the acronym means "Automatic Air Conditioning".
• Looking for "AAC" in the remainder of this document finds Fuse f7 (on page 2) as "AAC with integrated control additional fan motor (M4/7). This fuse is a 100 Amp rating, pretty large, my best guess on this is that this is your compressor and Air-Conditioning fan Fuse.
• Page 2 of this document says that this fuse is located in the "Front prefuse" box, and that it is located next to the air inlet of the air conditioning.

I could be wrong on the exact fuse above, but with some quick research that's where I would look, if you haven't already found this or fixed your Air-Conditioning problem.
For me a year ago, it was our AC compressor that went out. It was still barely operating and sometimes it would work just fine, but it seemed to only work when it was cooler, and not when it was warmer. NOT IDEAL! -Maybe that's when we really noticed it though, when we needed it most. These newer compressors are pretty neat in that it's not all on or all off with the clutch-plate style of yesteryear. Instead, these (and most newer AC compressors) are swash-plate type, where the piston stroke of all the (6?) pistons in the compressor can be varied. So when a little cooling is required, maybe 10% stroke. When it's really hot and lots of A/C demand: 100% stroke. Downside I've heard with a mechanic friend is they just don't seem to last as long. Our theory is that one part of the bore gets a whole lot more strokin' than the other.
In our GL's case, it was siezing up, and fortunately the controller notices too much load on the engine and cuts off command to the compressor to not shred a belt or grenade the compressor, leading to other A/C components to require replacing. Pretty neat, but also loads harder to troubleshoot, as you can't simply look at the compressor to see if the clutch is engaging or not, like the older compressors. Ah, the good ol' (rather inefficient) simple days..

Let us know what you found was the issue!

Tommyworx1

Great attention to detail! Thankyou for helping a newbie. I will take a look and let you know what I end up doing. I'm sure I will attempt to locate the right replacement compressor...not OEM as this is just a second vehicle. Then I will check here..to see if I can find instructions on DIY replacing the compressor.

cztexas

Really detailed information, and really helpful. Thank you so much. I have get my compressor and dryer done. My 2 cents:
1. I did not take the bumper out for the dryer. but I did tear down a small piece of plastic cover under the dryer to remove it (not the large bottom one). Forgot who I have mentioned in his thread, using locking plier can loose the T25 dryer screw, then replaced it with hex bolt. I found one from my old compressor, and it fits perfect. Thus next time, I can easily take it off by using wrench. Thank you for the tip of oil, I added a little bit as well.
2. I think you should not top the compressor with 110ml oil if you did not completely flush the system, or replaced all the major components (which are evaporator and condenser). 110ml should be the total amount of oil for whole ac system. Oil balancing should be better (measure the oil in old compressor, and that's the amount of oil should in the new compressor, plus 20ml per WIS document). Even for my case, there is no oil left at all for my old compressor, but I guess the oil did not loss, it may stay inside evaporator.

crypticresponse

Hello. I may have to tackle this job soon. Thanks for the info, everyone.

So do I have it correct that, once you remove the plastic fender liners, you can reach the compressor with the car on the ground on its, or does it need to be lifted? It sounds like you would just go in through the wheel well.

would you please confirm?

cztexas

I lifted driver side and take off the tire/wheel. Then there is enough room to reach compressor by using universal adapter.

crypticresponse

@cztexas , thanks for the comment. Can you also please tell me what size universal adaptor you used to fit in there? I believe I have the e-torx sockets. Were there any other tools that you needed or that would make this job easier? I will have to get the 17mm 12 point socket to release the serpentine belt. Thanks!

cztexas

I mean universal joint set, like this one: I also used extension. To me, I used very long one with the universal joint, and insert it via the hole under the bumper. You also need the metric E12 socket if I am not wrong, which is for the compressor bolts.

4loops

Funny enough I'm seeing posts on this thread as of late: my system has not been working in the dead heat of the summer as it was. You all have jinxed me! Due to my lack of time and A/C tooling, I had it diagnosed. I'd say those tools are too expensive to purchase to only be used a few times a decade, maybe -but then again this is the second time I'm having to dive into the GL, the Audi project has stopped cooling again, and the Jetta was acting up a couple years ago (which turned out to only be a corroded fuse), so who knows. Anyway, the diagnosis revealed that I must have a blockage between the dryer and the evaporator -so possibly the expansion valve. I'm told the compressor is indeed working at 100% -which is of course a lot of strain on the compressor.
I was told I could replace the dryer, as it could've failed, and that it could possibly be desiccant that broke loose from the dryer and is now creating a blockage further upstream. I'll have to look when I'm in there (the shop evacuated the refrigerant for me). -I also might try the method cztexas mentioned to reach the dryer (I really don't want to take the bumper cover off if I don't have to).

Also, a note to crypticresponse, If you're replacing your condenser (behind the intercooler, in front of the radiator), you'll have to remove the bumper cover and bumper. I was told it was a good idea to change the dryer and condenser at the same time (they're sold as a unit as an option) because the vanes in the condenser are so small that debris can easily get trapped in there and clog.
So, that said for me, I might try a flow test through the condenser if I can't find a blockage toward the expansion valve and evaporator. (If it's the evaporator, I'm really not looking forward to removing a dash, but I suppose what must be done must be done).

Further, on the universal joint set, I picked up a set of these from Hazard Fraught (Harbor Freight) for what, maybe $5-$8? If you hadn't already purchased the set and you have a H.F. nearby, it's worth a shot.

Good luck! -Let us know how it went!

VoodooShammer

Doing my 2007 ML350 today. Appreciate the write up!

texas008

MB dealer charged $2500 to replace the AC compressor, in 2018.
Before going to Mercedes Dealer, I called several indy AC shop and they said they could not work on Mercedes AC system.