takkie

Hello. I have spend some time troubleshooting the AC issue that I have on my 2009 ML350. It started last year but it was on and off. I drove to PA from NY on July 1 and the AC was just not blowing cold air - and after troubleshooting, i see some issues but i want to ask a few questions to people more knowledgeable than me.

Current mileage: 81k.

Current situation -

The AC does blow cold air, but they are not cool enough when turn to MAX / coolest, or at AUTO. It doesnt make me sweat but it doesnt feel like you are in AC Room. I thought it was becuase it was the sun directly shining on due to day time driving. But when i was driving back from PA, it was 10PM, and it was still not cool enough. The room temperate reads about 78 degree or so. I put a temperate into the vent, and the temperature coming out from Vent is 67F on the passenger vent, 69-70F on the Driver side vent. Rear middle vent is about 71F. I have used a MBII device and I can get the AC reading. From MBII, the Outside temperature does read correctly at about 31c (which is 88F) today. And each vent reads about 20C (Which is 68F). Radiator Fan does turn on when i press the AC button on, it turns off when i press the AC button Off. I hooked up a AC Gauge Manifold, and with the car/AC on - the Low side is about 55PSI and high side is at 150PSI with today's temperate about 88 degrees. With my MB II, I have a DTC Code of 9006 "Component A9 (AC Compressor) has short circuit". Note that this code has been there for atleast 5 years when I first got the MBII unit, but AC was okay and it just started this "Not cool enough" feeling this year. I googled the forum and the first thing I changed is the in cabin filter since i havent change it for 3 years. After putting in new cabin filter, theres no change to the situation.



My questions,

1) The fact that Low pressure reads 55 PSI on 88F, that seems to me i have enough freon, and its not a low freon or leaks issue. Am i right?

2) I believe the high pressure is too low, it should have been around 250PSI rather than 150 PSI - what would cause this high pressure too low issue?

3) The fact that the radiator fan does come on, its not a radiator or fan issue. Am i right?

4) I was trying to see if the clutch on the compression was engaged, but I dont see the clutch - the AC compressor pulley just spins the entire front of the compressor - is the w164 a clutchless compressor?

5) With the AC does blow out cold air but just not "strong" enough - does that mean the Compressor is okay (Despite the DTC code 9006)?

6) How do i check and confirm its not the evaporator or drier issue ? (I googled and most people have compressor, evap, or drier issue).

7) I googled and found some "AC Relearn procedure - but some say it doesnt exist for w164 - can you help me me know if there is such thing?

I found this document online, i was wondering anyone have the same issue?

https://static.nhtsa.gov/odi/tsbs/20...64657-2280.pdf


Thanks in advance.

Plutoe

you are either low on refrig or have a faulty compressor

mRaposo

It looks like a problem with the compressor's solenoid valve.

To confirm it is necessary to run a test with Xentry, which activates the compressor remotely, without using the panel commands - MBII does not have this option.

The bad news is that there is no new valve for sale by DENSO and you have to change the compressor completely, or buy a used one - the parallel valves don't work as the car doesn't recognize them - own experience.

takkie

I was able to buy the valve from ebay for 29 that has a diode. I replaced the valve and now its blowing 49 degree of cold air!

this is the one i bought:
https://www.ebay.com/itm/283284066725

takkie

I have fixed the problem Hopefully this will help others.

For DTC 9006 - all I did was clean the connection point W29/2 (TSB) by removing the kick panel on passenger side. Cleared the code, and it went away.

The ac was still not blowing cold air after the 9006 went away. I bought the AC Compressor control valve for 29.99 on ebay. (The one with diode). Bought a few R134 can ($6 a can) from Home Depot. Bought a vaccum / gauge kit ($129) from amazon. Then i took it to the shop to suck out all the r134a (Free). Vacuume the AC system at home. Checked to ensure the -30 is hold in the system to ensure no leak. Then got down to car, removed engine clad, remove electrical connection to the ac compressor from bottom of car. Use a c clip plier to remove the c clip. Use a flat head to pry the old control valve. Put the new one on (use the old oil from old control valve to wet the new oring), there was no oil leaked up, so i did not top off new oil. Connect everything again. Then with car off - hook up the first can of r134 - it sucked about half a can and didnt seem to suck anymore. So i started up the car with AC high, and the can were sucked in pretty quickly (a few minutes). closed the Low valve on the gauge, swap in another can, continue the process till i reach the 4th can. My car has rear AC so it needs 1220g which is 43oz. Each can is 12, so i left about 5.5oz left on the 4th can. I used a kitchen digital scale to watch it suck 7oz till i close the valve. During this process, the AC was blowing very cold air. I used a food thermometer and the AC is blowing 49degrees! Yeah! Before the fix, it was blowing 68degrees and it was not cool enough.

i will monitor this for some time and see, but i am some what confident this control valve was the issue and its an inexpensive fix. a shop wanted me to replace compressor for $1600!.

mRaposo

Good work. Good to know that there are now valves compatible with the ML compressor. I tried to find one 2 years ago and was unsuccessful.

crypticresponse

@takkie I saw your post and am interested in trying to swap out the valve in my compressor with one of those on eBay. Am I correct that the replacement of the valve is not related to the "diode" fix and the 9006 code? Or is it that the proper electronic control valve includes the functionality provided by the diode fix?

In my case, my compressor will function intermittently and blow very cold air. I believe it will function until it throws the 9006 and then it needs the code cleared to function again.

The way I interpret things I should 1) check the ground point, 2) try the diode fix, 3) control valve replacement, 4) replace compressor.

takkie

Hello. I am not an expert but i have done some research, and i had the same confusion as you also. I will share what i found with you and hopefully it helps you too.

I started researching into the 9006 error becuase my AC was not blowing code all the time. (Sometimes it is, but on a hot day, it is a bit on and off). With the MBII That i bought from amazon, i found that i have the 9006 error code.

From the internet / forums and various places, I found that there could be 2 possible 'fixes'.

A) Clean the ground point as per the TSB.
B) The diode fix. Which has 2 locations that you can fix, one with the top of the compressor, and the other one behind some covering. But requires buying a diode from amazon and solder/wire it to ground point.

I first attempted with the clean the ground point by the passenger seat. I cleared the code and drove for sometime, the 9006 did not come back again. However, my AC is still behaving the same - sometimes code, sometimes not cold.

Given that my 9006 is not there anymore, i figured i will not need the diode fix anymore. So i went straight onto the valve fix. When you buy the valve on ebay - it is extremely important to buy the one with the diode build inside the valve. (Note - this diode in the valve is not the same as the "diode fix" mentioned in here: https://mbworld.org/forums/gl-class-...-9006-a-2.html) Based on what i understand, this diode fix will not cause intermittent AC blowing cold then not cold)

Ebay listing will *not* say it has the diode, but it may say something like, "replacement for this this this brand of compressor only" which was my indication that it may have the diode. When you received the valve from Ebay - i noticed that it has a Diode symbol imprinted (Google it, it has a line and a triangle) at the tip of the valve where its supposed to be plugged in. I was quite confident that it has diode build in. At this point, i am also quite sure that the "9006 error" and the "AC blowing cold soemtimes" are not related to each other.

So i went ahead with the valve change - if you are attempting this, please make sure you have all the tools available before starting. It is quite difficult to unplug the valve to be honest. Also make sure you vacuum down all the pressure before you start. you absolutely need an angle needle plyer. Get a set from amazon that comes with 45 and 90 degrees. Once you are able to 'pry' out the valve loose - you will also have some difficulty yanking it out from the compressor because there is a heat sink thats in the way - it probably blocked it by may be 3mm or so, and you have to jiggle it back and forth to get it out and put the new one in. Once it is in - use a flat metal thing and a hammer to hammer it in tight - or else the c Clip will not lock in place..

the rest is just putting things together and refilling your freon.

thanks

Maj. Dundee

[QUOTE=takkie;8373957]I have fixed the problem Hopefully this will help others.

For DTC 9006 - all I did was clean the connection point R29/2 (TSB) by removing the kick panel on passenger side. Cleared the code, and it went away.

/QUOTE]

Please edit your post from R29/2 to W29/2.