bigslick7878

Putting aside the fact that I can't figure out how the hell the windshield defroster refuses to blow anything but 90 degree air (before today, all the time), the A/C decided to stop blowing cold air on the hottest day of the year. I drove it this morning, all was good and then all of the sudden tonight I don't have "hot" air blowing but it damn sure isn't cold either. Is this about when you would expect the system to need charging? Oh and also the outside air temperature sensor went up it looks like, went from -- past few days to negative 40 today. So looks like I need to replace that too but doesn't seem to be a big deal from what I read.

CaliBenzDriver

You are well on you way to have this figured out. Do not jump to over charging your A/C!

You know already the HVAC Controller read one of the temps sensor as Canadian winter so it's not giving you extra cooling.

Scan you car figure what lies temp sensors are telling the controller. Leave the refrigerant circuit alone for now.

bigslick7878

I'm not doing anything yet but I don't think the outside temp sensor has anything to do with the A/C. That sensor went out a week ago, A/C was working fine in that week til today. I have read that temp sensor going bad is very common and it is an easy fix (sensor is under the front bumper somewhere). But I have a Mercedes specialty shop I know can figure it out, I just want to educate myself before going in there.

CaliBenzDriver

Yes, let us know how fast that specialty shop can get your system working.

CaliBenzDriver

this may help you:

software update available 👍

bigslick7878

Interesting! I am looking up info on it now. But wouldn't it have been fixed a year and a half ago when the vehicles were affected, assuming mine was one? IDK thanks either way.

Edit - Looks like they have to scan it to find out, was hoping could enter VIN but that doesn't look like the case. At least if that isn't it they can tell me what it is while I'm there I guess.

CaliBenzDriver

You're right, it would be nice if all known problems were fixed each time the car gets serviced.

Outside recalls, campaigns are voluntary actions based on many factors.

It's good to be knowledgeable about topics of interest and bring up printouts to the service writer's attention.

bigslick7878

So we have a check engine light now to go along with no A/C. Car is running fine.

Question.....if I go to the stealer how much will they charge me to read the codes? I obviously will not be getting anything fixed there, but I am guessing there will be a charge. I was thinking go there so they can tell me any issues, then take it to other place to get the actual work done knowing exactly what the issues are?

CaliBenzDriver

Franchised dealers are not exactly ignorants about serving customers. Don't expect to come out with all the clues for $150 fee. Even $1000 is often not enough for casual repairs...

Save your time!
Go directly to the place that you know will fix your car right the 1st time... hopefully not AutoZone

MELODY7

I just had a similar issue that I'm still trying to resolve. Some of this info might help though. I went to the dealer and they charged me $230 just to diagnose. That recall did not help me unfortunately. What your issue sounds like to me is that your freon is leaking somewhere. Engine light comes on when you have low or no freon. Is your compressor turning on at least?

bigslick7878

Yeah forget that I'm not paying 230 for them to scan the codes. Anywhere can do that.. But that is very interesting what you said about the engine light and the freon. It is parked usually in a place where I would not be able to tell if anything was leaking. The check engine light was right behind the a/c not working so that could definitely be related. Didn't realize it would come on for that. I haven't listened for the compressor coming on I'm going to have to do that tomorrow. But thanks for the info.

MELODY7

I scanned my car with 3 different computers. Only one error code was appearing in regards to the compressor shutting off because my electrical board went into reserve mode. I didn't drive it for 3 weeks and even after driving it for a week the compressor wouldn't come back on. A battery usually goes into reserve mode when not driven for a while but should be 100% after driving it for a bit. The issue is that I have a s550e, its a hybrid (electric ac compressor). So many shops don't have the right equipment to diagnosis it. The first shop charged me $80 for a "you need a new compressor". Other shops were just honest and told me they didn't have the right equipment and to just take it to the dealership. "You need a new compressor" is code for we can't find the issue so lets just replace the entire thing. But hey, sometimes you actually do need a new compressor. My car has only 40k miles and there was no catastrophic event like a crash etc. But first check to see if your compressor is turning on. And if its not, find a shop that will jump your compressor and give it power. If it doesn't turn on after that then you actually do need a new compressor. Good luck and let us know how it went.

CaliBenzDriver

this sounds like the low power fault causes the software to disable A/C compressor even past the battery full status.

Simply reset the fault to let A/C resume operation: bingo, scanner payed for itself & saved time.

MELODY7

Thank you but how do I reset the fault?

CaliBenzDriver

Reset is done under 5mn with a scanner such as an iCarSoft... it pays for itself - See AMZ Prime delivery ✌️

MELODY7

Right. That was one of the first things I did and the same error code kept appearing.

CaliBenzDriver

Nice !
Then you move to next step ...
You now have yourself a confirmed fault.
Not just hunting a glitch

FAULT:
This reportedly looks like low voltage is forcing the electric compressor to remain disabled.

Forward :
From this stage, I am guessing your next best shot is to measure voltage with engine idling and eye ball the display while driving for Amps + Volts.

What sort of driving do you do:
long or shortfrequent, unfrequent

How old is the battery ?

Pls take a picture of the battery top, in particular the (-) post

BYPASS ... RUSH TEMP. FIX:
I know you want summer A/C ASAP... try to float the system battery with a CTEK to see if complete joy and satisfaction are resumed.

MELODY7

Thank you for your response. I am really convinced that its an electrical issue. I work from home and only really drive to the gym and a bite to eat everyday, so short frequent. On the weekends I might take longer drives. We've charged the battery to 100% but would need to get that picture for you to see how old it is. My next step is to jump the electrical compressor and see if it turns on. Do you think the auxiliary battery has any play in this? Haven't checked that.

CaliBenzDriver

Recap:
frequent short trips
battery floated to full
longer weekend trips

JUMP or NOT:
I don't recommend you simply about... jump power to your compressor...
We already know the controller is not allowing heavy loads. Is the system weak to supply 90Amps or the compressor overloading ?

Compressor is not known bad or is it needs testing
Why compressor is not getting powered.

(What's jumping compressor gonna do when nothing else knows A/C is running (engine Fan, blower etc) ? -- I answered that question and reconsidered that testing it is &#128077

NEXT STEP:
We got to figure what's causing this fault. Does your tool expose the "fault setting criteria" (Xentry does)?
This really is not a classic A/C issue... NOP!
it is a modern Benz power management fault.

I am recommending you go ahead and not skip over power checks indicated in prior msg.

++++ Edit ++++
Is electric compressor jammed??
Test what DC current load
Anyway you can spin it manually?

MELODY7

Right. I think its a power issue. If I jump the compressor and it turns on I'll confirm its not the compressor and its more of an electrical issue. A switch etc. Easy replacement, than changing the entire compressor.

CaliBenzDriver

Yes, at first I didn't think compressor was overloading supply and powering it would solve anything. Then i thought let's see the load...
You want to measure the load while pumping in a SHORT test.

We're trying to figure if compressor current is off chart or if power supply is faulty or both

You'll need a "DC-Clamp meter" to measure load.

BEWARE:
-- I am not sure what sort of DC power compressor uses
-- I wouldn't be surprised to see an 3-Phase aproximated AC motor.
Don't jump that to +12VDC!

Wiring will tell you DC vs. AC (picture !)

MELODY7

Is the secondary auxiliary battery even a factor with the ac compressor?

CaliBenzDriver

Nop, AUX does not muscle loads, specifically not convenience consumers.
​AUX supplies security when Main is not available. It has a really easy life doing not much.

On the fence:
We have to figure this question about overload:
- Car power supply is too weak
- A/C load is genuinely out of specs

Which is it
See Xentry's "fault criteria setting"
--> see previous posts for tests.

bigslick7878

So it was the outside temperature sensor that shut the whole AC system down. $120 fix. That was engine light too.

bigslick7878

So the wiring for the temp sensor was eaten by rodents (love that city life), That was fixed, new sensor installed......check engine light gone.......no other codes at all.....A/C still doesn't work.

. They tried everything but still nothing. They said the dealer might have to reset/reflash the computer or something? SMH.