Getting colder aircon VP

[stockhorse]

The aircon in the vp(6 cylinder) has just been serviced and isn't too bad,but I would like it colder.What can I do? A different compressor,different condensor? Or just put up with it?

[bradcad]

Simple stuff helps

Clean out the condensor. Consider painting it (very lightly) black- as black is more efficient at radiating heat. You could try insulating the cold pipes from the compressor. Also clean out your radiator while you are there and make sure the cooling system is working well. Excess heat will affect your air con.

Trouble is when aircons dont work so great there is usually a problem- I had my VT regassed and it was OK but by all means not great. Compressor packed it in a few months later, second hand compressor and it was great. Old compressor was lazy.

Could be compressor, TX valve, but its all very expensive to fi

[commsirac]

If the condensor is aluminium tubes and fins as most of them are, dont put paint on it. The majority of heat in an automotive radiator or condensor is removed by conduction from the fins to moving air, not IR radiation, paint of any colour will inhibit this by effectively offering a layer of insulation.
You do need to establish if there is anything wrong with your present system. There should be figures with which to check the performance somewhere, this would involve measuring vent temps against ambient temps when the vehicle is in the shade with engine at 2000rpm etc.
Typically people who service them, just regas them and check there is basically cold air coming out but certainly dont test them to spec, but possibly have some idea of what to expect out of a particular make and model through just having seen enough of them.
If the system measures within spec there isnt much you can do other than looking to upgrade the hardware, which most likely would start at changing the evaporator.........big $.

[stockhorse]

Thanks for the replies.I will make do with it for now but, I do have another compressor so may give that a go at the next service. I will get the drier etc done then to as this time they just regassed and did nothing else.

[bradcad]

I thought a radiator worked by the fins heating up, removing heat from the coolant passages then radiating the heat, which is removed by air passing through. I thought also that providing the layer of paint wasnt too thick that black helped radiate heat better than a bare surface?

[s_ikari2015]

unless you use a metalic paint it's really not worth painting.

It's probably best to just have it replaced or cleaned out if you can. Again the trick of replacing insulation might also help to keep it colder. Also replace the hood lining if it's getting thin and old, will help keep the air flowing over the bonnet into the fresh air vent a bit cooler.

[commsirac]

I thought a radiator worked by the fins heating up, removing heat from the coolant passages then radiating the heat, which is removed by air passing through. I thought also that providing the layer of paint wasnt too thick that black helped radiate heat better than a bare surface?

The primary method of heat transfer is by conduction, air molecules coming in direct contact with the metal surface of the "radiator". If the radiator was able to get rid of the majority of its heat by "radiating" then it wouldnt need air to pass through it as the energy would leave as IR, it would need to glow near red hot to do this effectively. You can get a feel for how much radiaton they emit by putting your hand approximately a foot from a hot automotive radiator. You should be able to feel the heat of the radiator. Have a fan blow air across the gap between your hand and the rad, parallel to the surface of the radiator and not blowing on your hand. Repeat the experiment using an electric bar radiator.......the result may surprise you.
Typically it is only copper/brass radiators that end up being painted to stop corrosion. I havent seen many Al radiators painted. We all know that they the build up a layer of Al2O3 very quickly, whether this is more thermal insulating than a layer of fine matt black paint, I dont know......but putting paint upon this layer would be unnecessary to stop corrosion and only offer more insulation.

Stockhorse: Are you are using the recirc function(which you should be if you are trying to keep the temperature down). If so, reduced underbonnet insulation would perhaps help the system rather than inhibit it. If you are using fresh air then one thing to look for is that the rear of the bonnet seals properly as hot air can be ducted directly from the engine bay into the ducts below the screen. You can check for this by operating the fans at standstill and checking for any air coming through the rear edge.(more of a problem with much older cars)

[kopper69]

Can you grab a temp meter and tell us what the temp is at the vents. A system that has just been regassed normally sits at about 5 degrees.

[Kung-Foo-Kamel]

Get it re-gassed with some HR-12

Doesnt need to be retro fitted, this gas works in old R-12 systems and new R134A systems

Hy-chill did this to my VN at one of our training courses, they got my air conn down to 3 degrees with a digital temp gauge in my vent, the air-con was amazing after they changed the gas, less load on the engine as well, that R134A gas is useless on a 30+ day but HR-12 works awsome, I even had frost come out at times

Here's a link to there website

HyChill Refrigerants - Manufacturers of Hydrocarbon Refrigeration Gases, HC's, HR12, ER12 - CFCs, HFCs, HCFCs, hydroflurocarbons, R12, R22/502, R290, R600a, and R134a Replacements

Cheers

KFK

[commsirac]

Kung foo Kamel, the VN being manufactured in 1988 or thereabouts was designed for r12(freon) (now not widely available or permitted in cars manufactured after 1994), so it is entirely likely that if your system was regassed with r134 that performance would be inadequate unless considerable changes were made to the system. It is perhaps no surprise that regassing the system with HC(which has properties similar to r12) improved performance considerably. I wouldnt expect to see drastic improvement in systems that are designed to run on r134a.

Vent temps only tell you something when the system is fully loaded in hot weather. Otherwise the vent temps are a function of the tx valve characteristics and the properties of the gas being used. However, I do believe that hydrocarbon refrigerant (hychill) has been demonstrated to improve performance even in r134 systems where the tx valving is not optimum for this gas. Is the HC gas long term compatible with all seals and refrigerant oils? Many manufacturers will not warranty their compressors if run on hydrocarbon.........

Why dont the car manufacturers use it? They still have the $ signs etched into their retinas from the Ford Pinto problem.......hydrocarbons are flammable. The manufacturers of Hychill will tell you its nearly impossible to get their refrigerant to start a fire/explosion in a car.......I think so far the stats back them up, yet there is no value for the car manufacturers in using it as it is possible to design a system that cool properly with r134a.

[Kung-Foo-Kamel]

It works even better in a system that is designed for R134A, They did a VT at the same time as mine, it got colder than mine

I dont give a crap that its flamible, so's the petrol in the petrol tank, so's the LPG in the LPG tank

Anyway its just a suggestion, it wont cost him much, just a regas, if it doesnt work then change it back, Im getting my VZ done as the aircon is crap when its over 30 degrees

I was under the impression that the VN and VP Aircon system is the same anyway, pretty sure mine was a R134A system

[commsirac]

Kung Foo, please dont take what Ive posted too personally, I actually use hychill in some of my vehicles that used to run r12 and it works great, however, we want to give people all the information here:

It works even better in a system that is designed for R134A,

It could be true, however, I wouldnt hang my hat on the results in one vt commodore.

I dont give a crap that its flamible, so's the petrol in the petrol tank, so's the LPG in the LPG tank

Good logic in itself, however, the aircon system was not built with any inherent safe guards to not endanger the occupants of the cabin or releases at the condensor in the event of a front end collision. It is possible to simulate explosions in the cabin due to sudden evaporator leaks and fires starting at the condensor......, all are very unlikely situations which at the moment havent been realised in real use. However, the owner of the car should be made aware of before converting their system to this gas. The gas is banned for use in North America

I was under the impression that the VN and VP Aircon system is the same anyway, pretty sure mine was a R134A system

I wasnt......the regulation didnt come into 1994 that r12 was not to be fitted and GM and Ford didnt change til then.

[vt_lover]

I would like to add that the oil is a big issue when changing refrigerants. some use mineral while others use polyester. if you put the wrong refrigerant in, the oil sort of 'curdles' like milk, as you can imagine this isn't very good for lubrication. auto air con guys do a very short course in a/c, some as little as 1 week long, so to train a guy on proper refrigerant selection in a week is almost impossible. if you go in there asking for a particular type of refrigerant they are more than likely to just give it too you without knowing the consequences. i would advise using only the refrigerant specified. also rule of thumb is you should get around 10-18 degrees difference from air-on to air-off the evaporator (depending on revs and fan speed). so if your getting 3 degrees at the outlet i would be worried that there is a problem with the evaporator which can cause liquid flood-back to the compressor.

if you want more capacity i would advise a few things:
1. keep the condenser clean, even just a little dirt can drop efficiency dramatically in summer. a fortnightly hose out cant hurt.
2. avoid using the 3 or high fans speeds for the first 5-10 Min's of operation. high fan speeds on start up cause the refrigerant to flash boil too early which can take a while to settle down.
3. if you get any work done ask them how many microns of vacuum the system was evacuated to. anything under 200 is good. if they cant answer, ask how they know for sure ALL of the moisture is gone out of the system?
moisture is the best way to lose efficiency.
4. if the cabin gets too cold use the heater to adjust the temp rather then turning the a/c off. a refrigeration system takes around 10 Min's to stabilise so if you turn it off you will have too wait another 10 Min's until it works properly once you've turned it back on.

[blownba]

Hychill is o.k as a cheap alternative BUT it has a terrible oil return capacity so on a hot day when the system starts to work harder Hychill will starve your compressor of oil and the results are obvious.
Thats why compressor manufactures will not warrant their compressors when running on Hychill.
If you ask around none of the "real" players in the air con industry will use hychill or even allow it into their workshops.
Even when retrofitting it is true that HC refrigerant can perform better in some instances but when pushed to capacity HC's refrigerants cause more trouble than its worth.
Like what has previously been said moisure and contaminates will affect performance considerably so on a retrofit I quote for what I think is the right way and also the quicker and cheap way.
My right way would involve removing the compressor and dissasembling all joints and flushing the complete system with nitrogen and proper a/c flush fluid than replacing all o-rings and TX valve (R134a compatible type) and the high pressure/ temprature cut out switch and filter drier and than running a correct R134a lubricant for the peticular compressor. Than evacuating for a considerable period and regassing with R134a.
Also I would attempt to improve condensor air flow by straightening fins and making sure all seals and foam between radiator and condensor are in place.
The results are always considerably better than just dumping a bit of ester (oil) in the system and dumping R134a in it as most mechanics would do for a retrofit.
The point is you get what you pay for and its usally only the guys with the porsches and mercs ect that will get it done the right way.