Inoperative aircon.

[Rob7seven]

Anne and I spent much of September touring around southwest France. On the journey south from Cherbourg, the aircon gave cause for concern, it just didn't seem to be very effective in the increasingly warm conditions as we travelled southwards. After two or three days, it stopped performing altogether, the temperature outside was approaching 40 degrees at times, and no matter how I set the controls, all that came through the vents was warm air, no cooling effect at all. We eventually switched off the aircon altogether and got breathable air by opening windows, something I rarely if ever do, and not much fun on Autoroutes. After SW France, we headed north to the Loir, a charming little river, much nicer than the better known Loire, which the Loir joins at Angers, and with lower temperatures, the lack of any cooling was less of a problem. On returning to the UK, I had the car looked at as soon as possible. I've become a bit disenchanted with the local MB dealer, whose assessment was "...seemed to be working OK, carried out quick tests, no faults present". All they found was that the system was overfilled by 120gm, 750gm instead of 630, so they'd emptied the system, refilled it with the correct amount, and reloaded and updated some software, but surely none of this could explain the complete shutdown of the system? The car had never been anywhere that warm before in its sheltered UK existence, all it's ever been asked to do is plus or minus a degree or two, but they couldn't provide any explanation for the period that it stopped working altogether, which worries me not a little. We may well be returning to the south of France next year, and certainly wouldn't want to go through the same experience again.

Now, the aircon seems to be functioning OK, though in home temperatures at the moment, it's difficult to tell. If I set it to Lo, I do get slightly chilled air out of the vents, and if I set it to the other extreme, I do get warm air, though I'm sure it's not the 15 to 26 degree range I'd expect, and it also takes longer to respond than I'd expect. I'm taking my car to Startech this Wednesday, and hope that they'll find something that MB missed, as I'm sure there must be some kind of fault in the system, if there is, I'd be more confident of them finding it.

Has anyone else had an experience like this, and any suggestions as to what I should tell Startech to point them in the right direction?

 

[Blobcat]

I recommend you find an independent AC Specialist (not just someone with a 10 minute course on a portable machine)
Explain your issues and they'll likely have come across them previously and be able to rectify

 

[S500 Pete]

When the AC is set to low it should just keep blowing on maximum cold. Normally this is checked with a thermometer probe into one of the vents. My car during the hot summer here was still very well chilled at over 37 degrees outside, started blowing really hard to get the temp down after being parked and then eased back as it got to 21 degrees inside.

 

[Rob7seven]

A bit mystified why my original post didn't attract more interest, only Blobcat and S500 Pete appear to have seen it. I thought I'd posted in the right place, but it never reached 'New Posts', or anywhere else reasonably prominent as far as I could see. All I'd hoped for was some relevant comment that might have been helpful, but where did I go wrong?

My car went into Startech a couple of weeks ago, I'd called to ask their opinion, and they clearly knew what they were talking about, so I left the car with them. The work took them over two hours, and they phoned later that day. They explained what they'd found, and I've pasted the "Work carried out" text from their invoice below.

"Carried out functional test of heating/cooling function, all working OK. Connected diagnosticmachine, stored dtc for fresh air recirculation air flap, flap has a mechanical defect. Run teach in for air flap, working OK at time of test. Run teach in for flap and test again, still working OK. Checked values when operating hot and cold buttons, both flaps are adjusting correctly, customer to monitor. Advise to replace this flap motor dashboard and air distribution box has to be removed, suggest not required at this time. Investigated heater not getting hot enough".

Startech admitted that they bore some blame for not doing a deeper check when they'd first had the car in a few weeks earlier, and without any fuss at all, they charged me only a fairly nominal amount this time. As before, I expect only Blobcat and maybe S500 Pete wil see all this, but I'd be interested to see any comments. Unfortunately, I've only managed about 5 miles in my C300 since what I hope will prove to be a successful repair, I've spent two weeks recovering from what is probably my second dose of Covid, as anyone who has experience this knows, it's a very unpleasant experience. Two initial jabs, and three boosters, so five in all, but having doctors in the Family and being married to a retired nurse had made me a model patient, I just do what they tell me, so I try to look on the bright side, things could always be worse, couldn't they?

 

[Blobcat]

A bit mystified why my original post didn't attract more interest, only Blobcat and S500 Pete appear to have seen it. I thought I'd posted in the right place, but it never reached 'New Posts', or anywhere else reasonably prominent as far as I could see. All I'd hoped for was some relevant comment that might have been helpful, but where did I go wrong?

My car went into Startech a couple of weeks ago, I'd called to ask their opinion, and they clearly knew what they were talking about, so I left the car with them. The work took them over two hours, and they phoned later that day. They explained what they'd found, and I've pasted the "Work carried out" text from their invoice below.

"Carried out functional test of heating/cooling function, all working OK. Connected diagnosticmachine, stored dtc for fresh air recirculation air flap, flap has a mechanical defect. Run teach in for air flap, working OK at time of test. Run teach in for flap and test again, still working OK. Checked values when operating hot and cold buttons, both flaps are adjusting correctly, customer to monitor. Advise to replace this flap motor dashboard and air distribution box has to be removed, suggest not required at this time. Investigated heater not getting hot enough".

Startech admitted that they bore some blame for not doing a deeper check when they'd first had the car in a few weeks earlier, and without any fuss at all, they charged me only a fairly nominal amount this time. As before, I expect only Blobcat and maybe S500 Pete wil see all this, but I'd be interested to see any comments. Unfortunately, I've only managed about 5 miles in my C300 since what I hope will prove to be a successful repair, I've spent two weeks recovering from what is probably my second dose of Covid, as anyone who has experience this knows, it's a very unpleasant experience. Two initial jabs, and three boosters, so five in all, but having doctors in the Family and being married to a retired nurse had made me a model patient, I just do what they tell me, so I try to look on the bright side, things could always be worse, couldn't they?

Some threads don’t get a lot of traffic, sone don’t, I’ve never really worked out why.

Your attachment didn’t upload correctly so we can’t see it Unfortunately.

I see and read all threads (unfortunately…)

 

[EmilysDad]

people read threads and don't comment when they have nothing to add ...

 

[M80]

Sorry I didn't have time to read the posts.

 

[Dean Fletcher]

I must admit sometimes I’ll pass if it’s a super read

 

[mioba]

I think @EmilysDad post is spot on. I hope he reads this and comments further, If not maybe he is not paying enough attention or I am wrong........

Perhaps people read your post (based on the title) as it could be interisting or they may have seen something similar.

People may not respond since having read your post they realise they simply cannot assist further beyond 1) whats been posted already 2) thier own (in)experince to your particular issue 3) they just don't want to.

Always look on the bright side of life whatever cards you are dealt with!

 

[Richard Moakes]

Overcharged with gas and high ambient temperature could have led to very high compressor head pressure, which can trigger AC shutdown as a protective measure.

It’s crucial that the system has the correct weight of gas filled, as the pressure varies according to superheat at the evaporator and sub cooling at the condenser.

I would want to know how it got a nearly 20% overcharge of refrigerant?

 

[pgh13]

Plus one for finding an independent specialist.
Mine was iffy for a while; taking 10 mins to provide cool air from first start of the day.
Got it checked at one of the recharge places who couldn't diagnose beyond gas or no gas.
Eventually went to Compressortech in Warwick who diagnosed a duff solenoid on the compressor and replaced the compressor, for £450, which, when I see compressors on the Bay at £200 plus, didn't seem that bad (do I sound convinced?)

 

[Rob7seven]

Overcharged with gas and high ambient temperature could have led to very high compressor head pressure, which can trigger AC shutdown as a protective measure.

It’s crucial that the system has the correct weight of gas filled, as the pressure varies according to superheat at the evaporator and sub cooling at the condenser.

I would want to know how it got a nearly 20% overcharge of refrigerant?

I've learned quite a lot about MB AC sysyems through my recent experiences, and I think you're pretty much correct with all of that. What you said would explain why my car's system more or less gave up once outside temperatures went over 40c, and also why it came partially back to life once outside temperatures lowered. Worryingly, Startech said that the system could have been, permanently damaged, though so far they haven't found any evidence of that, but they've told me to watch things carefully for a while.

On those responsible for the initial over-gassing, we'll never know, but until Startech did the last service in March 22, no-one but Mercedes had ever touched the car, The MB factory in Bremen, and two UK MB Dealers, would the system have been gassed in the factory before shipping, surely it would, but both UK dealers clearly failed to check the car properly, and they won't ever be getting a second chance.

 

[Gw2Ns]

I Have a 2001 SLK that was only blowing HOT. Everyone pointed to a stuck control valve (Easily accessible at Passenger side Strut post} needed to be disassembled and cleaned. I Pulled the electrical connection to check the controls. All seemed OK so i put it back together to tackle another day. (NOW IT WORKED) Next time it quit I stuck s thumbtack into the side of the connector and squeezed it with a pair of pliers to dimple the contact tube a little. NO MOR PROBLEM. 2 min fix
Good luck

 

[rifiki]

Use the AC all the time and the AC will last for years (decades) without any problems