Just add gas until it gets nice and cold.

The only way to be certain how much gas is in the system is to suck it all out then inject the correct charge by weight, this is how commercial systems work.

8 hours ago, J.R. said:

In which case you have wasted both your time and your energy,

Cheers for the indirect support mate.

Right just to get the facts straight as Ken seems he'll bent on being a tool when I got the car the ac generator had a fault the guy had purchased a replacement but had not fitted it and yes the gas had all leaked out I've now fitted the new pump a friend has been round and vacuum tested it for leaks I then purchased the correct gas not cheap eco crap as I had already read about it being useless and at the same time I purchased a proper pipe and valve to introduce the gas eith a pressure gauge on it I simply did not put enough gas in I hope you feel better now Ken that I've been forced to give up half my life's story just to satisfy you 👍😉

45 minutes ago, Stewartasb said:

Ken seems he'll bent on being a tool

OK. I'll block you since you clearly don't need any advice from anyone.

Yes I do but you don't give advice just unneeded derogatory remarks yours I can do without thanks.

13 hours ago, J.R. said:

if you are measuring using VCDS be aware that it reports absolute and not guage pressure.

 

This hasn't been my experience, and I did a couple of things at lunchtime to double-check, though I got a bit confused at the time.

First thing I did was hook up VCDS and a pressure gauge simultaneously with ignition only on, engine off.

I saw 5.6 bar on the gauge and 5.4 bar reported by VCDS (Lite, registered).  Because I was confused about what went where, this was actually the low side gauge/pressure, but with system off and not run recently, I believe that doesn't matter.

 

Then I battled like hell to unplug the connector from G65 and plugged it into a brand new, genuine G65 that was hanging free in the atmosphere. VCDS said 0.0 bar.

 

When I did actually run the engine with both gauges connected, VCDS reported a pressure lower than did the high-side gauge (about 1.2 bar lower).  As far as I can see this is the opposite of what you'd expect if there was indeed a mismatch in reporting scales. I suspect that the <£40 manifold set is poorly calibrated.

Edited 3 June, 20215 yr by Wino

I tested some while back and like you just ended up confusing myself more

 

I have to check the system soon so I will do the back to back test like you did although I dont think that I have a spare working G65 sensor, its possible though.

 

I will report back and if I have a conclusion I will write it down amongst my AC dossier graphs, notes etc otherwise I will forget once again.

10 hours ago, Stewartasb said:

 I've now fitted the new pump a friend has been round and vacuum tested it for leaks I then purchased the correct gas not cheap eco crap as I had already read about it being useless and at the same time I purchased a proper pipe and valve to introduce the gas eith a pressure gauge on it I simply did not put enough gas

Unless you introduced the gas via the bleed port on an AC manifold set while the system was under vacuum (you close off the port to the vacuum pump and bleed in the refrigerant) then the system will have been full of humid air at 1 bar atmospheric pressure, if you managed to pressurise the system to say 4 bar using the cans (and you would need double the amount they say based on weight) then the air now at 4 bar pressure will be taking up 25% of the system volume, the water vapour that it contained will have condensed & unless you replaced the drier will spread around the system possibly damaging the pump but certainly freezing after the evaporator orifice restriction.

 

I am sure that you hope you have purchased the correct gas but its illegal to sell it within the EU and virtually impossible to find, the Ali-Express sellers have to resort to calling it various inventive names like "air freshener" or "AC test fluid" I had 3 orders from different sellers that didn't arrive (I suspect they were siezed) before I bit the bullet and paid a fortune for a 13kg R1344a cylinder and even then nobody would sell it to me unless I was a qualified frigoriste, the exception being a Lithuanian seller & even he has probably been shut down.

 

There are no restrictions however in selling propane gas despite the fact that it could cause an explosion.

Edited 3 June, 20215 yr by J.R.

I thought that the commercial AC service machines vacuumed out the contents, then injected nitrogen and fluorescent dye to test for leaks before refilling the system with the correct weight of refrigerant and PAG oil.

I seem to remember reading that positive pressure dry nitrogen leak testing is only done if vacuum isn't held sufficiently, and that dye is frowned upon these days for some reason. @Tech1e have I got that anywhere near correct?

I suppose it's adding dye to the refrigerant and using that to leak location test is what's frowned upon, if you know there's a leak.

Edited 3 June, 20215 yr by Wino

Yes they do, or should do, in France not many do the nitrogen test or have the die.

 

I am just a hobbyist with a manifold set, vacuum pump and a 13kg R134a cylinder and a timeshare hole in the ozone layer

 

I tried weighing how much was taken on by the system but every electronic hook type scale I have bought ties out and resets to zero So I fill till the high side pressure is what my graphs say it should be.

 

As for refilling with the "correct" quantity of oil that would require the operator to know that the system started with the correct amount and how much they removed when evacuating the system, a calculation and precise dosing to refill.

 

What actually happens is they all have these automatic machines, they make 2 connections press the start button and let the thing do its business for 30 minutes while they make some money doing another job or serving another customer. They say the machine does it all automatically but I have yet to find an operator who even knows where to top the thing up with oil or what type of oil it has in its reservoir if any at all.

 

As I get to see what I vacuum out & it never has any oil mist I have yet to refill any, I have noy yet bought a vessel with the valves etc to introduce it through the bleed port.

I had trouble with machine operators last time I got the Fabia recharged.  I knew I had some leaky o-rings in the high pressure side of the circuit, so asked the boss man to make sure to only empty the system, give me the car back to do the o-rings, then I'd bring it back for them to vac down again and refill.

 

Sounds easy, right? It didn't quite go that way, but we got there in the end. 

 

11 hours ago, sepulchrave said:

I thought that the commercial AC service machines vacuumed out the contents, weighed the contents against spec for a fresh fill,  then advised you there was a leak or refilled the system with the correct weight of refrigerant and PAG oil.

Edit in-line, underscore

33 minutes ago, KenONeill said:

Edit in-line, underscore

 

Why do they bother weighing all the old crap the machine hoovered out, it seems complex and unnecessary?

19 minutes ago, sepulchrave said:

 

Why do they bother weighing all the old crap the machine hoovered out, it seems complex and unnecessary?

You can think of another way to determine whether or not a system which isn't empty has a leak? Also, I checked and scales similar to the ones I've seen in use are about £100 a set.

1 hour ago, KenONeill said:

You can think of another way to determine whether or not a system which isn't empty has a leak? Also, I checked and scales similar to the ones I've seen in use are about £100 a set.

 

Yes, inject pressurised nitrogen and test leak down, if the system holds pressure then recharge, if not identify leaking parts, replace and retest.

 

Duh?

27 minutes ago, sepulchrave said:

 

Yes, inject pressurised nitrogen and test leak down, if the system holds pressure then recharge, if not identify leaking parts, replace and retest.

 

Duh?

OK, how is this meant to be simpler than before and after weighing the receiver that the old refrigerant is pumped into?

Every system leaks, in most cases when people put their vehicle in for a recharge it is because the system has lost some refrigerant through the normal losses across the flexible hose materials and to a latter degree the pump seals.

 

A vacuum test is the quickest way to detect if there is a leak and a pressure test is the best way of detecting where it is.

 

There is no benefit in weighing the gas recovered other than for accounting and possibly charging the customer by weight for the recharge, if oil mist is recovered and seperated then I can see the value of replacing the same amount but I am unconvinced that this happens with the automatic plug in & leave machines that all the operators use that demand zero technical knowledge of the user.

53 minutes ago, KenONeill said:

OK, how is this meant to be simpler than before and after weighing the receiver that the old refrigerant is pumped into?

 

Because weighing the old charge is inaccurate and pointless and makes the machine far more complex and unreliable than it needs to be, the weight of the fresh charge is easily calculated by how much is removed from an assayed bottle and the oil content is similarly calculated by the quantity used.

 

Simple arithmetic is much more accurate than metrology.

2 hours ago, sepulchrave said:

Because weighing the old charge is " inaccurate and pointless" and makes the machine far more complex and unreliable than it needs to be,

1. Do you want to argue with a manufacturer of laboratory grade scales that their machines are " inaccurate and pointless"? That's what you've just said to me.
2. Do you want to argue with a manufacturer of laboratory grade scales that their machines are "complex and unreliable"? The receiver and scales are 2 separate items, with the receiver sitting on the scales.
3. Actually, have you ever had an air conditioning system regassed? I have, and had a chat with the operator whilst he was working.

17 minutes ago, KenONeill said:

1. Do you want to argue with a manufacturer of laboratory grade scales that their machines are " inaccurate and pointless"? That's what you've just said to me.
2. Do you want to argue with a manufacturer of laboratory grade scales that their machines are "complex and unreliable"? The receiver and scales are 2 separate items, with the receiver sitting on the scales.
3. Actually, have you ever had an air conditioning system regassed? I have, and had a chat with the operator whilst he was working.

 

1. No it's not and I'm not looking for an argument, you are.

 

2. Absolutely not, but I would tell them that their equipment won't survive five minutes in a garage workshop environment.

 

3. Of course I have, and I can tell you the operator had absolutely no idea how the equipment works, it's designed to be idiot proof for a reason.

3. Of course I have, and I can tell you the operator had absolutely no idea how the equipment works, it's designed to be idiot proof for a reason.

 

Absolutely spot on!

 

Thats not to say that there will not be an operator who knows what they are doing and has some understanding beyond that of how the vehicle system works, the failure modes, the symptoms, the weak points on various vehicles who you could learn a lot from.

 

Its been 15 maybe 20 years since I have encounterd one though, about the same amount of time that the manufacturers started producing idiot proof equipment for the Kwik-Fit type centers.

 

And then you need to have enough knowledge of the subject and a good enough measure of the person you are dealing with to know whether to give any credence to what they have to say, that only comes through engaging with them on the subject, if they clam up or become defensive its a very bad sign.

 

Every day on here or other places I see myths perpetuated by people repeating what they have swallowed without reflection or contemplation, "a mechanic once told me.................." "I was always taught................" (but I don't understand why), its a hell of a lot worse in this country where the whole education system is based around retaining (believing without question) what you are being told and the ability to regurgitate it and not an understanding of the how & why.