AC not working

[E55BOF]

The heater is working, the aircon isn't, properly at least, if the lowest it will go is ambient. The Halfords check showed there was a problem. If the problem is only low pressure, not no pressure, you might find a DIY top-up will work, which I suspect is what you're intending to try. Good luck if you do; I hope it works. (Measuring the pressure at the LP port doesn't work for MB systems; something to do with the type of compressor, I believe.)

FWIW, my wife's Mazda MX3 had a slow leak in the system, and I had to top it up every Spring. I did it a little at a time, until it blew satisfactorily cold, to avoid overfilling it. It was fine for five years, and fine when she sold the car after that time, though I did tell the buyer about the problem.

If you have, or can borrow, an iCarsoft MB II or similar (don't know about earlier versions), you can measure the operating pressure when the system is running; 13-14 bar is what you're looking for. My CLK had precisely 0.0 bar when I bought it, so I knew it had a leak, not just low pressure.

 

[Uky]

Never attempt to refill a system without verifying that there is a proper
amount of compressor oil in it.

The compressor oil is circulating together with the refrigerant. In many cases,
a leak can be detected by a dirty spot on the radiator as a result of a stone shot
or around a gasket as a result of a leak.

When testing the system, any remaining refrigerant is vacuumed out of it
following a pressure drop test where the system is pressure tested and monitored over an hour or so.

If there is no pressure drop, the system is refilled with the proper amount of refrigerant,
compressor oil and a fluorescent additive.

The system is tested and then left over night
with pressure monitoring connected. If nothing has leaked out during the night, the car is
handed over to the owner. If there is a leak, it can be spotted using an UV-flash light.
(But actually, this green fluorescent can be seen using a normal LED flash light.)

Since the 2008 C-class shares the platform with the E-class coupé:

I experienced a leak in my C207 M/Y 2009. A weak spot is the lower left side of the
radiator. That place is where one of the AC hoses together with a pressure sensor
is located, exposed to salt and wet winter roads. The aluminium corrodes and leaks formed
together with dendrites gets its way past the gasket. The situation gets worse by the steel bolt that risks getting
stuck as the "nut" is the threads in the aluminium parts. Mercedes saved 1 cent by not
using an external steel nut on the opposite side. Loosening this bolt was "a bit nervous".

I fixed the leak myself. Drilled all the way through the aluminium. Used a longer bolt and
a separate steel nut on the opposite side. Carefully cleaned the joint from the dendrites using finest
possible metal sand paper, used *two* new gaskets instead of one and went to an authorized MB service
station and had the system tested and refilled.

I had access to a service pit when doing the repair. The plastics that covers the
bottom parts of the front radiators has to be removed in order to get access.

 

[D2028]

If you have, or can borrow, an iCarsoft MB II or similar (don't know about earlier versions), you can measure the operating pressure when the system is running; 13-14 bar is what you're looking for. My CLK had precisely 0.0 bar when I bought it, so I knew it had a leak, not just low pressure.

That's interesting, I didn't know you could do that, every day is a school day.

 

[Petrol Pete]

Not really because it's not telling you the pressure. Just a color coded readout on the suction side which is not accurate. Pressures should be read on the high side determine if you have enough freon.

Its accurate enough to tell you if the system is empty. Thats enough to stop people wasting money on DIY topping up , instead take the car to a specialist.

Like I said in my post . tells something ...but not a lot.

 

[drmacf]

Orion Motor Tech AC Vacuum Pump and Gauge Set, 1/3 hp 4 cfm Vacuum Pump Manifold Gauge Kit with Leak Detector 4 Hoses & Accessories for R134a R22 R410a, A/C Vacuum Pump Kit for Auto HVAC Systems​

Anyone used this before?
This and will buy Halfords, 72 quid got a can of R134a

Sorry, was thinking of scrapping the car but holding on to it for sentimental value. Cannot risk spending 400 quid for ac repairs, just done 350 quid on brake disc repairs and next month is the insurance. It's guzzling away cash
So would test it with this orion, it seems like a good kit and covers all angles? leaks, oil, seals and vacuum? Will watch you tube videos and see
Rule here is if the pressure is ZERO = stop the diy and take it to an expert. Zero = leak and not just low pressure
If it's just low pressure, then proceed to halfords,l buy a can of r134a and fill it up.

Can't seem to find that sticker, under the bonnet. This its peeled off a long time ago. Wrote to MB's head office, asking for specifications, such as psi etc
Hope they reply and then I should be good to go

 

[E55BOF]

It's R134a. R12 was not used after 1995.

Are you thinking of buying that kit to see if there is pressure in the system? As an alternative, you could, of course, go back to Halfords and ask the chap who did the test whether that 'warning' was for low pressure or no pressure. That shouldn't cost anything.

(My Mate Dave used to just uncap the LP port and briefly press the Schrader valve in a little with a screwdriver, barely a touch, keeping his face well away. If there was refrigerant, and hence pressure, in the system, a tiny bit would escape; if not, it was empty. This is, of course, illegal, but nobody was ever watching...)

 

[drmacf]

Just got the info from MB
The refrigerant used is R134A and pressure is measured in grams 590 g

Is this information enough or do I need any more? Such as psi ?

 

[Petrol Pete]

The pressure is not measured in grammes , 590g is the amount of liquid that is required in the system for it to function properly. When this liquid is transformed into gas during the operation of the AC .

It is (essentially) the pressure of this gas that is then measured by the equipment gauges to inform the technician of the relationship between the high pressure and low pressure side of the system when running.

 

[GeeJayW]

Just got the info from MB
The refrigerant used is R134A and pressure is measured in grams 590 g

Is this information enough or do I need any more? Such as psi ?

Not trying to be a d!ck here, but given that you may not be fully conversant with A/C systems, I strongly recommend taking your car to a specialist or living with the absence of A/C. Trying to recharge it yourself when you don't have the kit, knowledge or experience to fully diagnose why the refrigerant has been lost in the first place is a recipe for throwing good money after bad.

You might get lucky, but the refrigerant has escaped from the system already so there is a leak somewhere. Simply putting some more in might work briefly, but without determining the source and size of the leak, it may well just come out again and it could happen quite quickly.
-------
I'm not an expert in automotive a/c systems, but:

The refrigerant is a material that changes state from liquid to gas and back to liquid. Under pressure it is a liquified gas. As it passes through an expansion valve into the evaporator (located somewhere in the dashboard heater assembly) on the low pressure side of the system it turns into a gas. In order to do this it takes in heat energy from the surroundings. The gas then makes its way to the compressor which turns it into a high pressure gas at a temperature of about 40 degC. It then passes to the condenser (located at the front of the car by the radiator) where the heat energy is given up to the air flowing through the condenser matrix, turning it back into a liquid. Then back to the beginning.

Typical modes of failure are, dried out compressor seals (often due to lack of use), a leak caused by stone striking the condenser, o-ring seal failure around the expansion valve/evaporator assembly.

The 'amount' of refrigerant used is determined by its mass, in this case 590g which is matched to the internal volume of the system such that the operating pressures and temperatures are in the correct range. Without looking at the PV diagram for R134a, I don't know what the pressure would be at 40 degC, so can't suggest a number for that.

In addition to the refrigerant, lubricant for the compressor is also present.

Having the correct amount of refrigerant and lubricant for the individual system is essential.

 

[DSM10000]

Just got the info from MB
The refrigerant used is R134A and pressure is measured in grams 590 g

Is this information enough or do I need any more? Such as psi ?

Are you seriously telling us that you think that the Gram is a unit of pressure?

It is clear from your posts that your understanding of the operation of car A/C systems is very limited which is fine.

That's why we employ specialists to take on the tasks outside our own skill sets. It will be far cheaper and safer to hand the problem over to one of these.

 

[drmacf]

Just got the info from MB
The refrigerant used is R134A and pressure is measured in grams 590 g

Is this information enough or do I need any more? Such as psi ?

Got some more info from my MB dealer

A/C pressure when A/c not on - 0 - 4 bar low pressure, 0 - 6 bar high pressure

A/C on - 0 - 2 bar low pressure, 10 - 15 bar high pressure.

 

[ALFAitalia]

1) The AC system is a sealed system and the refrigerant is not a consumable so if it's low, it means that you have a leak.

Not quite .........Up to 10% loss per year is normal.......even more is acceptable with some car makers. Many still suggest a bi-annual regas!!!

See this....

AC Facts and Myths | Air Conditioning AutoTechAC

autotechac.com

 

[DSM10000]

Got some more info from my MB dealer

A/C pressure when A/c not on - 0 - 4 bar low pressure, 0 - 6 bar high pressure

A/C on - 0 - 2 bar low pressure, 10 - 15 bar high pressure. is this helping you?

I am unsure how this information is helping you?

You don't have the professional equipment or knowledge to properly measure these values when the A/C is running and, if the gas pressure is too low the compressor clutch will not engage so they cannot be accurately measured.

You seem, despite the overwhelming advice given, reluctant to take the car to an A/C specialist or to a garage that has the equipment to test and, if possible, regas the system?

Nearly all garages that offer regassing will not charge you if the system is shown to have a leak.

You say that you don't wish to waste money on the car if it has faulty A/C but have spent £72 on a DIY top up etc.

You could get it tested and regassed properly for less than that.

 

[Pontoneer]

Do not try to refill it yourself.

It needs to have the exact amount of refrigerant added after a pressure or vacuum test. There is also a special oil that needs to be of the correct volume.

You can buy all the stuff in Halfords , including the gauge , lubricant , dye and it is easy to DIY once you have the tool , and cheaper than paying the monkeys to do it .

 

[ALFAitalia]

Loads of places around here do a complete test (vacuum and pressure) and regas for less than the £72 can you are considering!! Its £65 at Halfords.....and there is a specialist near me that does it for £49!.....but my mate does mine for £30!!!

 

[alabbasi]

Not quite .........Up to 10% loss per year is normal.......even more is acceptable with some car makers. Many still suggest a bi-annual regas!!!

Yeah and the FDA allows for up to 9 rat poops per 1KG of wheat. That's not normal or acceptable, just CYA. Car A/C systems can reach pressures over 300PSI, it's either sealed or it leaks.

 

[Pontoneer]

A car of that age ? R134a , thankfully , the new stuff is way more expensive. As said there should be a sticker under the bonnet , often on the front cross piece that has the bonnet latch holes. It states what refrigerant , what volume is required and percentage of PAG required.

Sticker sometimes go missing during accident repair

The ports are different for R12 or R134a , and presumably different again for whatever the latest refrigerant is - it ought to be impossible to put the wrong gas in because the connections just won't fit ; just like with butane/propane bottles - different regulators for each gas .

 

[DSM10000]

You can buy all the stuff in Halfords , including the gauge , lubricant , dye and it is easy to DIY once you have the tool , and cheaper than paying the monkeys to do it .

Most places offering A/C regassing for that car are offering it for between £60 to £70.

How is that more expensive?

Plus, no need for the derogatory comments, the machines may be automated but the companies providing do stand by their service via guarantee and the OP clearly is no expert in this area.

 

[Pontoneer]

I am unsure how this information is helping you?

You don't have the professional equipment or knowledge to properly measure these values when the A/C is running and, if the gas pressure is too low the compressor clutch will not engage so they cannot be accurately measured.

You seem, despite the overwhelming advice given, reluctant to take the car to an A/C specialist or to a garage that has the equipment to test and, if possible, regas the system?

Nearly all garages that offer regassing will not charge you if the system is shown to have a leak.

You say that you don't wish to waste money on the car if it has faulty A/C but have spent £72 on a DIY top up etc.

You could get it tested and regassed properly for less than that.

Halfords auto centre still charged me when I booked an ac service along with a new set of tyres for my SL . Told me the condenser was holed and wanted £££ to repair , scoffed when I declined , saying it was a convertible after all and ac is just a nice to have , not an essential , as I always have the roof down when it is warm . I didn't argue the toss over the bill as I'd paid in advance and they still ran the test on it .

After that , I just bought the kit to do the job myself , and the gauge indicates the state of charge of the system , I wouldn't recharge an empty system but will top up a low one .

 

[ALFAitalia]

Yeah and the FDA allows for up to 9 rat poops per 1KG of wheat. That's not normal or acceptable, just CYA. Car A/C systems can reach pressures over 300PSI, it's either sealed or it leaks.

If you cant be bothered to read this scientific paper on the subject then one of the summery points is...

"The relative annual leakage rate is the percentage of the measured difference against the norm charge, which is annualised in the same way as above. It is found to be 6.9% per year."

https://climate.ec.europa.eu/system/files/2016-11/leakage_rates_final_report_en.pdf