Car Air conditioning

[pancake]

I know this is probably the wrong place to ask but you guys know so much about phase change/refrigeration that one of you may know the answer to my problem.
The air con in my car didnt work when i bought it so i took it to a friends garage and they hooked it up to the machine that purges the gas and refils it.
When this was going on i was watching the machine and it did a test checking for pressure or something like that and it passed fine, and it refilled to the correct values stated on the label in the engine bay.
Turned the air con on and the air was nice and cold.. which lasted for around a week, now it is just getting warmer and warmer air coming out of it day by day... any ideas?
i dont have the cash to take it to a proper air conditioning place so i am looking for pointers.

[RyderOCZ]

The system has a leak, probably in the Evaporator, but it could be anywhere.

There is a Die that you can put into the system to detect the leak, it is UV reactive. You have them put it in, use the system for a couple days....then go and look for the leak with a blacklight.

Ask your friend about it.

[DetroitAC]

Sure, that's an easy one. You have a leak, have a shop inject fluorescent dye into it, and wait a few weeks. You could also buy a can of R-134a with the dye in it and a low side adapter and take a guess at how much you should add. If you have a noticeable decrease in performance it's low more than 4oz, since that's the standard amount of reserve in auto AC systems, so it'd be safe to put in about 6oz yourself. Buy a cheap low side can adapter, keep the car cool, and warm the can up by sticking it in 100F water (use a thermometer!, too warm and you will burst the can). The refr4igerant will flow right in, you can just ballpark it by the weight of the can to get 4-6 oz in there. In a few weeks, look for the bright green spot, or take it to a shop so they can find it (there is a leak that they will have to fix anyway).

DO NOT USE a stop leak. They will turn your expansion valve into a shutoff valve, and your compressor into a bucket of very small parts.

[pancake]

Thanks guys.. sounds expensive so i will just suffer in the warm weather.. why did i buy a dark colour car :(

[star882]

The UV dye is pretty cheap.
You might be able to put epoxy around the leak to slow it down to the point where it's usable. Not as good as a proper repair, though.

[Gray Mole]

Shame you're not closer, I could help you out with it.

There's so many places and so many ways you can have a leak in your AC system it's not funny. Rubbing pipes, rubber clips (haven for corrosion), condensor, etc.

The plus is that it's fairly rare to get a leak in the evap, but if it is it's a pretty big job if you need the dash out, which you almost always seem to have to do :rolleyes:

It's not easy to do the job yourself unless you can degass and all that but like they say, if you can ebay yourself a can of the 134a that comes with low side adapter and UV dye included, it's pretty easy to spot a leak most of the time.

If you can give me the make and model, I may be able to tell you some of the common spots for leakage, I have to do auto aircon every day :rolleyes: among other things, so might be able to give you a heads up on the likely trouble spots.

Gray

[wdrzal]

if the leaks in the evap , you need a electronic detector ,so it can (smell) the refrigerant comming out the vents since you can't see the evap to look for dye.

also look around line connections and the front seal of othe compressor for
oils stains. were ever your leak is you will have a oil stain, yours sounds pretty large to empty in a week, shouldn't be hard to find.

you could move farter north!

[pancake]

its a rover 45 :( been nothing but trouble since i got it.

But shouldnt the automated purge and refil machine they used at the garage have spotted a leak, at one stage it said checking for vacum or something and it passed that ok.

[Gray Mole]

that's the thing, a leak that takes a week in an automotive system is pretty small.

The Vacuum pumps are also pretty awful (I am SO tempted every day to take mine to work) most of the time, as it's not 'needed' to pull deep when it's not going below freezing.

Beyond that, when I asked for nitrogen and a digital vac gauge at work they laughed at me :mad:

I had a car in yesterday though, and did a quick pressure test to about 7 bar, then recovered and pulled it down for 30min, with a 10min vacuum decay and it lost nothing that could be noticed without a digi gauge.

Soon as it was charge and actually running, at around 8-9bar is was pissing out the high side pipe. Easy to see, but I charge EVERY car with UV dye now, to save the time later if there IS a leak. It's what every shop shoudl be doing, save time, effort, and gas.

So I had to recover the gas again, and lost all of the time for the job, when a 10 bar nitrogen test would have told the whole story in the first place :rolleyes:

So I'm not surprised that they didn't find it, when it's a leak that takes that amount of time, it's rare to find it with anything other than time, and UV dye.

Gray

[Gray Mole]

Oh yeah, and I don't see a lot of Rover's (thankfully ;) ) at work, but I've got a mate who's a Rover tech, will ask if there's a couple of trouble spots to check first.

I still say, get some dye in, and you'll find it easy :D

Gray

[pancake]

ok thanks, i may have a look for some and give it a shot if it is cheap.

[pancake]

think this would stop a leak if it was tiny?

http://cgi.ebay.co.uk/DIY-AIR-CON-TOP-UP-KIT-FOR-R134a-SYSTEMS_W0QQitemZ140004941728QQihZ004QQcategoryZ98 89QQrdZ1QQcmdZViewItem

[runmc]

If it only lasted for a week, I would say you had a pretty good leak.

If your not going to pay to fix it, then get you a cheap low pressure gauge at the auto parts and a 16 once can of 134a. Add some refrigerant according to the gauge. Then you will have the gauge to use next time you need to charge. When you get the cash - fix the leak.

[DetroitAC]

Yes, that stuff will stop a tiny leak. It hardens when it is exposed to air, so it finds the pinhole, leaks out a bit and hardens. It's going to goop up your drier, your expansion valve possibly, and your compressor. Guess what happens if it doesn't stop the leak and you have to take the system apart??? IT ALL HARDENS! and you can pitch every component in the garbage can! You can't recover refrigerant with that stuff in it, it will clog up the recovery cart and contaminate the refrigerant in the recovery bottle. Garages run a test to see if cars have sealant in them, and usually turn them away or charge extra and use a "special" (piece of junk) recovery cart.

Sorry pancake, but you have most likely a leaking o-ring or compressor shaft seal or something else, and snake-oil-in-a-can is just going to cause more headaches for you. This is one area where there aren't a lot of short-cuts to getting it fixed properly.

Dye in a can of R-134a is about the same price. It's better to know what you're dealing with, and where the leak is before you go messing things up.

[SiGfever]

The rubber hoses are the first place to look in an automobile a/c system. After a while they start dry rotting and begin leaking. But as stated check all mechanical connections for oil sign. The seals in the compressor are also known leakers.

[wdrzal]

Sure miss the days when a 30# can of R12 was $25.00 . Even if you leaked 8 ounces a week,it only cost you less than 2.00 a month to just top it off and keep it working thru the summer.

[Gray Mole]

Yes, that stuff will stop a tiny leak. It hardens when it is exposed to air, so it finds the pinhole, leaks out a bit and hardens. It's going to goop up your drier, your expansion valve possibly, and your compressor. Guess what happens if it doesn't stop the leak and you have to take the system apart??? IT ALL HARDENS! and you can pitch every component in the garbage can! You can't recover refrigerant with that stuff in it, it will clog up the recovery cart and contaminate the refrigerant in the recovery bottle. Garages run a test to see if cars have sealant in them, and usually turn them away or charge extra and use a "special" (piece of junk) recovery cart.

Sorry pancake, but you have most likely a leaking o-ring or compressor shaft seal or something else, and snake-oil-in-a-can is just going to cause more headaches for you. This is one area where there aren't a lot of short-cuts to getting it fixed properly.

Dye in a can of R-134a is about the same price. It's better to know what you're dealing with, and where the leak is before you go messing things up.

Yup

Most of the stop leaks for aircon are rated to repair a 300-400 micron leak anyway, and that's more like a 6 month leak than a one week if you know what I mean.

I've never been a fan of ANY stop leaks, as they all tend to do more longterm harm than they do short term good.

Just keep in mind though, that the longer you wait to sort it out, the more chance there is of other 'issues' coming up as well. An empty system tends to gather moisture and crud, and can develop a lot more leaks and other problems in short order.

I'd also recommend a new dryer unit/cartridge (depending on system) if it's been open to the air for any period of time really, or you'll just be 'storing' all that junk in there if/when it does get repaired.

Gray

[hatemi]

I have one question. or maeby even some more actually :D

My car AC has been leaking practically the whole time I have had it. One spot(dont know if it leaks that much from somewhere else) was the O-rings that connect the high and lowside tubes to the expansion valve. I changed the O-rings and managed to destroy the thread in the expansionvalve that the flange bolts on(2000 model Golf). I guess I used too much force... Then I took the valve of there and made larger thrad to it. I also had to make the bolt hole larger on the flange and that is when I might have messed the tubes up somehow. Now I cant get it to hold preasure. Everytime i tighten the bolt after some point it just starts to leak more....I just hate aluminum and O-rings!

So the question is this. If get that leak fixed somehow do I need to change the oil. If yes, then how should I do it? The drier will propably need to be replaced too.

[sl4ck]

Better way to change the oil is get the compressor from your car, turn it downside and let the oil out to some kind of measure recipient, then replace the oil with the same quantity.

If it has leaked some oil, you have to look for your A/C Car datasheet and find the quantity.

sorry about my english isn´t the better, but i think you understand me

[wdrzal]

hatemi,you know there are special tools that look like color coded rings to disconnect the lines on most auto's. they usually come like five to a set. I can't remember their proper name ,I always called them quick coupling disconnect tools.

[runmc]

I know this is probably the wrong place to ask but you guys know so much about phase change/refrigeration that one of you may know the answer to my problem.
The air con in my car didnt work when i bought it so i took it to a friends garage and they hooked it up to the machine that purges the gas and refils it.
When this was going on i was watching the machine and it did a test checking for pressure or something like that and it passed fine, and it refilled to the correct values stated on the label in the engine bay.
Turned the air con on and the air was nice and cold.. which lasted for around a week, now it is just getting warmer and warmer air coming out of it day by day... any ideas?
i dont have the cash to take it to a proper air conditioning place so i am looking for pointers.


Maybe it's overcharged and doesn't have a leak at all. :wasntme: :wasntme:

[Xeon th MG Pony]

best ways to repair a sriped thread is to clean the bore out with a solvant to remove any oil or greases, then get the right type epoxy, let it set in the hole, drill, tape, and rebolt it much more care fully.

[blowsion]

look if your fan is spinning, could be pressure building up and that cousing the leak.

[DetroitAC]

VW uses a fitting to the TXV we call a tube-o, and the good news is that it is very common. An auto AC shop will be able to make a new suction hose end for you by splicing a longer section of hose to your existing suction hose, and then crimp on a new tube-o fitting. They could also cut the old hose off and braze a hose crimp fitting to the old line, and then run hose to a new crimp tube-o. The liquid line on a Golf I think is aluminum pipe amost all the way from the condenser, they'll want to braze a new hose crimp to the old line and run hose from there, or they might be able to just cut off your bent up tube-o and braze a new one on.

Changing the oil or not depends on how much time the oil has been exposed to air. Your car uses PAG which is hygroscopic (absorbs water). Short bits of time here and there are not a big deal, long periods of an open system you should replace it. The oil all circulates with the refrigerant, and is randomly deposited in the components at shutdown or after recovery...the point it's not just the compressor. The entire system must be flushed, which means the txv has to be removed anyway, can't flush through it. The compressor has to be removed and sort of flushed with clean PAG. Your car uses a SD7V16, has a plug on the crankcase which can be opened for this. It's an involved process, not cheap if you have an AC shop do it.

[hatemi]

I think Ill try to fix the leaking TXV joit myself before I will get an AC shop to look at it. It costs 100€ for them to even open the hood :D It has been exposed to air for an hour or so when I was tapping the TXV with 8mm therad. Then I vacumed and filled it with R134a and found out it leaked. Did that a few times again trying ot make the loint leak free but eventually I jsut quit. It hs been like that for few months now, but there shouldnt be any air in there. I havent turned the AC on without any gas in there.

[wdrzal]

doesn,t matter if you run it or not. Eventelly all the refrigerant will leak out to it equilizes at 1 atmosphere. then during the heat of the day the gas inside expands raising the pressure forcing out more gas. As night comes and the gas inside cools,it goes slghyly below 1 atm. thus being in a slight vacuum sucking in air at the same place the gas leaked out.

[Xeon th MG Pony]

yup, no matter what by now you have plenty of moisture and air in there

[Pete]

Driver faster, windows down, sunnies on and the tunes al lthe way up, free aircon and no parts to go wrong!!!

Also Tuesday the 18th in the uk is ment to be the hottest day ever!!!!

However it's soon going to pass so your problem will pass as cold wil lset in and heat be needed

[hatemi]

SO no AC for me then :) I will not put that much money/efort into fixing it. Might aswell rip the condencer out of there to make more room for bigger IC ;)

[Xeon th MG Pony]

If you have the money to blow to get it all redon why not, if no then I wouldn't bother, just turbo charge a pelt cooler and bring ice cold lemon aid every where with you!

[DetroitAC]

If you don't want to pay to get the old oil flushed out...don't. Those components may be just fine, they may you for some good years of having AC. If you stop using them and let them get more full of water and dirt, they are ruined anyway.

I'd say fix those tube-o connections, and measure all of the oil that you can pour out the system, and replace that amount with new PAG. Charge it up and get your money's worth from those components. You already paid for them!

[Jort]

detroitAC,

what sort of oil is used in autoAC?

because i am going to repair a leak in a Ford this week :)

[DetroitAC]

For R-134a, different compressor mfg use different PAG, mostly the viscosity is different. Ford mostly uses PAG 46, which is probably the most common.