kponti

I am having a weird AC problem in the last couple of weeks.

When it works, it is cold as ice and runs perfectly. When it doesn't, it simply does not work. Now 90 to 95% of the time, it works. It's the other 5 to 10% that it likes to shut off that pisses me off.
It only does not work when I first start the car after it has been parked for a few hours or overnight. And that has happened 3 times in the last 3 weeks (I restart my car minimum of 2-3 times a day going to and from work or anywhere else I go).

The first time I sort of noticed it was after a car wash and the ac took quite a while to cool back down. Then normal for another few months. Then 3 weeks ago it simply will not blow cold air when it was raining (even though garage kept the first time it happened.). Stayed warm till I got to work. Blew cold a few hours later when I went to discount tire during my lunch break that day (was dry then), blew warm 2 hours later when I picked it up from discount tire. Blew cold on my way home from work later that day. Worked fine for a week.
A week later simply stopped blowing cold after work (had just rained). So I drive to MB dealer and purchased new ambient temp sensor and replaced, been fine ever since.

Yesterday after work, no cold air (cold as usual in my way to work). Now this time no rain, no car wash, no water involved for the first time. Checked refrigerant levels, still the same on low side at 35psi at idle

OK I'm baffled, no codes or flashing lights (haven't checked via star though). I fully expect it to suddenly work this morning as usual which will further add to my confusion. Any ideas?

kponti

And the weirdness continues, ice cold this morning, working like nothing was ever wrong before

shardul

iTrader: (1)

Bring it by and we can connect it to das

kponti

Thanks Shardul, I'll be texting you today

biggking

There's a TSB for one of the a/c lines, please take a look at this thread:

https://mbworld.org/forums/w211-amg/...-replaced.html

kponti

I was reading that thread just a week or so ago thinking, "that sucks for that guy in this heat. Glad mine was just a moisture problem." Oh how wrong I was lol. I may have that looked at after I have Shardul play with DAS on my car

kponti

New symptom, car's ac actually does go cooler periodically if you leave ac on long enough. But it's short lived and warms back up. Like a pendulum except it stays warm to warmer longer than cool

Yacht Master

What year is your 55, do you have the rest button?

kponti

2005 and no, no rest button. Also holding down the auto button has not worked for me to get to the hidden menu

novae500

Running into ac problems myself. Will be taking to my indy, since after adding some R134 to it and it was cool for a day and back to hot air. So must have a leak or blockage somewhere.

Yacht Master

Well then Star is the only way to find out what the problem is.
Checking the pressures is not necessarily the best way to determine state of charge, because we have variable displacement compressors.
There is only one way to check the charge, that is to recover the existing charge and recharge with the exact specified amount of R134a, other wise 3 oz plus or minus and the system will work like crap.
Any good AC shop can do this provided there is not any sealer in the system, they will not recover tainted R 134a.

In your case my best guess is that your expansion valve is sticking.

The removal of the rest button was a real downgrade for the 05 and on.
MB wanted the AC diagnostics back in house.

Hulk

Expansion valave could be an issue and I do agree with a full evac and full vacuum , then add freon again, Changing the dryer at that time will help also

hank55

Mine would get hot if i sat in the car and let it idle but would get cool again if the car was moving. Also i just found out that the frony blows cool but the rear blows hot. Just dropped mine off to the dealer under warranty.

novae500

def update us on what the issues are causing this. Believe for you at least the Heater exchange valve for rear blowing hot.

kponti

Yes for hank it will be the heater exchange valve under the windshield. I already replaced mine when I had those symptoms some months back.

Hulk

Yup, heater control valve, changed mine a few weeks ago also

rawdvm

I, too, am having a strange A/C issue. The front blows cold for anywhere from 30 sec to 30 minutes. Then, the fan slows & the cold air goes away. If I turn it off, wait a few seconds & turn it back on, it sometimes starts working normally & sometimes not. The strange thing is that the rear vents blow cold all the time & my DAS shows no codes & all the sensors are working. When the car was at EC in Houston, John checked the refrigerant & it was ok. Any thoughts?

TheOtherDodge

I have the same issue where all of the sudden the blower motor stops blowing air. I don't know if the AC actually quits working because there is no air anymore. Then a few minutes later, everything is fine. This has only happened about 3 times in the 3 years I have had the car...

hank55

heat exchanger valve and apparently my ac was a little low was what the dealer just informed me.

novae500

Well got a chance to take to my Indy. Ended up being leaky o ring seals from the receiver drier. Could see all the greenish oil liquid around the seals and pooled onto the plastic splash guard. Waiting for parts to arrive next week

kponti

Just got back from indy, no vacuum leaks, proper levels of refridgerant in system. OK one thing I left out, I topped off the system with the interdynamics refridgerant, the nasa inspired one about a month ago. Car was stupid cold afterwards and I loved it.
So to eliminate that being a possible issue, I had him evacuate and vacuum the system. Put in the proper and fresh batch of r134 and pag. So far so good but it's only been a few hours

kponti

Just a heads up, so I had no detectable leaks which will mean the nasa inspired r134 is probably not to blame for my ac problems (no clots in the recovered refridgerant). However ever since I had all my refridgerant recovered and fresh batch put in, ac has been working perfectly (though takes a lil longer to cool now in 90plus degrees than with that stuff in it).
My thoughts are that stuff stays at temps much cooler than pure r134 and causes the expansion valve to close up a bit too soon to prevent icing up of the evaporator core. End result is my *** stays sweating and the car tries not to freeze over.

Today however is the real test..... I parked it where it will be in direct sunlight for the day. If it works around 5pm, well that will mean problem solved, and I can put this mess behind me.

Hulk

Yes full evac and vacuum helps a lot should have changed the dryer at the same time

kponti

I thought about that, and might explain why I think the car takes longer to cool. But by that I mean in a quarter of a mile to half a mile the car is at comfortable temps with settings at 76 degrees after being parked outside in 90 plus degree weather. Also the car is black on black on black

I didn't because if that wasn't the problem, changing out parts will require another vacuum etc and the dryer will be replaced then. For now I just want the damn problem fixed and of I need more cooling (like when the KC goes on) dryer and seals will be replaced as well

Hulk

I definately recommend you find the problem before you do the KC