Air Con Recharge with STP gas and gauge

[Bentley]

Hi All
Just wondered if anyone has any experience of using the STP gas and gauge on a Z3 3l engine. My air con was not getting cold, checked compressor was engaging etc and all seemed ok so decided to try recharging myself.
Followed instructions and the gauge showed low, did the recharge with the engine running and compressor engaged, filled until the gauge was in green. All seemed great lots of cold air coming out of vents.

My worry is that although gauge needle shows green when the air con is working it goes up to the red Warning when the air con is turned of, any body know if this is correct or had similar experience.
Thank you and any help appreciated

 

[Rudyrov]

IMHO- That type of recharge is a temporary measure to get you through the summer, in most cases the reason that your AC is empty is that you have a leak, a leak that must be fixed to restore the integrity of the system long term. Problem is, AC is time consuming and can be alot of work. If you are mechanical and enjoy working on the car, invest in a set of gauges or rent some and try to find the leak or you will be putting alot of Freon into the air.

 

[Bentley]

Hi IMHO. Thank you for your reply, You may be right but it has not had a recharge in 10 years and I have read that the gas does disperse naturally over time.

Do you have any thoughts on the question that I asked ?

 

[Bentley]

Hi All
I probably posted my question prematurely. Just spoken to STP Tech support, very nice and knowledgeable man. He explained to me that you do have to check the pressure when the compressor is running. It is NORMAL for the gauge to show red when connected to the air con point and compressor not running.
Thanks all
Ben

 

[Stevo7682]

To charge an air con system properly you need to evac the system then vacuum leak checks then fill from vacuum state our air con machines in the depots carry all this out in one procedure

 

[Althulas]

You can also give your self some nasty chemical burns from this stuff if your not careful. For the sake of £50 I got my Honda CRV checked in spring and was just low
gas and has been fine since. Have the zed to sort to when I get another compressor.

 

[Rudyrov]

Hi IMHO. Thank you for your reply, You may be right but it has not had a recharge in 10 years and I have read that the gas does disperse naturally over time.

Do you have any thoughts on the question that I asked ?

Hi again, and just FYI... IMHO means "In my humble opinion."

OK, in that case, first you need to verify that the system is empty or has so little gas that the system will not run. This can be done by testing for pressure at one of the Schroeder valve's or by connecting a set of gauges to the system. I say this because if the system does have pressure you don't want to overcharge it.
If there is little or no pressure you could charge it by using one of the quick charge methods you mentioned, it certainly isn't the ideal method as it is designed to get you a quick fix so you can take it home for a proper repair, done the right way. Keep in mind that if there is any other major reason the system stopped working it still may not work, for example a bad pressure switch, a bad A/C clutch or a plugged expansion valve to name a few.

 

[t-tony]

You need to be VERY careful checking for pressure on the system by opening one of the Schrader valves. The refrigerant has a very low boiling point and in contact with skin (assuming you're alive) will readily boil leaving very nasty wounds. We are only allowed to use the A.C. equipment at work after attending a training course.

Tony.

 

[Rudyrov]

You need to be VERY careful checking for pressure on the system by opening one of the Schrader valves. The refrigerant has a very low boiling point and in contact with skin (assuming you're alive) will readily boil leaving very nasty wounds. We are only allowed to use the A.C. equipment at work after attending a training course.

Tony.

I agree Tony!

 

[Redline]

I understand the gas contains lubricant for the system. Running the ac with little or no pressure can cause wear (and consequently future problems). If you know it's low or empty it's probably wise to keep it switched off.

They might have pressure sensors built in that switches them off but I've no idea if that's the case or not.

Regassing ac is a competitive business. For the cost (£40-£50) it's easier to take it somewhere with the machine to do a full evacuation, test and recharge. Do it every couple of years in the springtime (although ac is great at removing moisture from the air even in winter so will help clear windscreens more quickly).
Air con is never on the service items. You'd think it would be but it isn't. Even 3-4 year old cars suffer problems.

 

[t-tony]

The gas does not contain lubricant, it is added as a separate item along with a tracer dye if required (to find leaks by using a UV light) when the system is re charged. When the system is evacuated you get a print out of the amount of gas and oil that has been removed. Yes they usually have a sensor which turns off power to the compressor if the has level gets too low.

Tony.

 

[mrscalex]

To charge an air con system properly you need to evac the system then vacuum leak checks then fill from vacuum state our air con machines in the depots carry all this out in one procedure

I have a mobile guy do mine. He's as honest as the day is long and I trust what he tells me. He has this to say on his web site - so proceed with care!

We don't do 'top ups' - whilst it is possible to get a car air con system working by just adding more refrigerant, it is very bad practice. Without knowing what refrigerant and how much is in the system, it is impossible to correctly charge a vehicle. Also, the system needs to be vacuumed for around 20 minutes prior to recharging, in order to remove any residual air and moisture. The aerosol 'top up' cans available at one of the large car accesory shops do not mention that fact. The result of 'topping up' is usually an expensive repair.

We NEVER recharge a system without leak testing with Oxygen Free Nitrogen (OFN). Although it is more expensive to use OFN for leak testing, it is the only legal and safe way. Some garages are using compressed air to test, which adds moisture to the system and can leave residual oxygen which when mixed with refrigerant and compressed can cause explosive destruction of the condenser, and we would NEVER test for a leak using Refrigerant.

Leak Testing by vacuuming alone is misleading and, if relied on solely as a leak test, is in most cases, illegal. Most of the low price offers seen at some tyre fitters will only provide a vacuum test. Which is why they fail to diagnose most of the leaks on cars they recharge.

Insist on an OFN pressure test BEFORE your car aircon system is charged!

Remember - it is a criminal offence to recharge a system that you know or suspect is leaking. If the system is empty - a leak must be suspected.

 

[t-tony]

Overfilling an A.C. system reduces its ability to cool as much as one low on has. There are other options for testing for leaks too. It's ok to use compressed air as long as the system is 're vacuumed again beforbefore charging.

Tony.

 

[Redline]

We NEVER recharge a system without leak testing with Oxygen Free Nitrogen (OFN).

Insist on an OFN pressure test BEFORE your car aircon system is charged!

Remember - it is a criminal offence to recharge a system that you know or suspect is leaking. If the system is empty - a leak must be suspected.

The OFN bit is really useful information.

The ineffectiveness of a vacuum leak test makes sense. Using a vacuum to test for leaks is hardly the same as a pressure test. A vacuum is likely to constrict any leave with normal air pressure forcing any leak closed.
What is the normal pressure that ac is charged to?

 

[Bentley]

Thank you all for taking the time to help me, it really is a very interesting subject and I have learnt so much about car AC. I have read every reply carefully and if I had read them before buying the kit probably would have been frightened of attempting the job. Like loads of you guys I like to do as much as possible, plenty of research can be done before tackling a job, I have always done my own car maintenance, central heating stuff, computer stuff, DIY etc probably as you all do. I also find the so called expert is not as good as they should be due to tight time schedules. Apparently when they do AC in a garage (as pointed out above) the system is emptied and refilled by weight of gas to manufactures spec. A garage person I spoke to told me that they give these "simple" jobs to the apprentice and this apprentice put in 10 times to much gas and then told the customer that it was faulty on arrival, so much for the expert job.

Anyway it is done now and all seems ok, there must be thousands of people doing this job themselves when you look at the amount of kit being sold for it.
Must say sorry to @Rudyrov about IMHO you can tell I am not a social media person. I wont forget that in a hurry (who would have thought I would have learnt that from car AC recharge).
I now have a problem with my indicator/main beam switch, better start a new post for that, hopefully I will get as much good feed back.

Again thank you all, this is such a great place.
Ben
https://zroadster.org/members/rudyrov.1221/

 

[petecossie]

Bentley,
Appreciate that you like to do work yourself, I'm of a similar nature myself, but something like the A/C maintenance is fairly specialist job. It has a number of pitfalls as have been pointed out already.
I had A/C sorted on my car today, used a reputable Auto Service depot who I've used before for fitting tyres that I previously purchased new from Camskill Tyres.
The work was fully explained prior to starting the job and was definitely not done by an apprentice.
I have loads of service history and detailed bills covering the last 12 years or so, the last time the A/C was touched was way back in April 2007. Although the A/C worked OK the coolness level was not what I'd had on my previous model of this car which I explained to the guy at reception desk. The job took 50 mins, the gas was removed and pressure test carried out. The amount of gas taken out was in line with my thoughts that there was no major leak but the system had just been depleted since 2007.
New gas installed with added lubricant and tracer dye. You could now hang meat in the car it's that cold!!!
Normally costs £45, but got it for £19.50 on a Groupon Deal. A bargain I thought. Especially when I looked in at Halfords and saw the cost of the STP re-gassing gear.

 

[t-tony]

Especially when I looked in at Halfords and saw the cost of the STP re-gassing gear.

Says it all Pete Stores market that stuff in such a way as to make you think you're saving money.
As you said there are many pitfalls and also quite a bit of danger too.

Tony.

 

[Ianmc]

I thought there were strict regulations about this ie capturing old gas, leak testing etc. Have never considered it a DIY task, might be wrong though.

 

[t-tony]

No CFC's in AC refrigerant nowadays. Was illegal to lose that old type gas, don't know about 134e.

Tony.

 

[Bentley]

Pete, That is really good value for money. If I could have got it done by a reputable service that I had confidence in I would of course been down there in a shot. At the price you paid it does make the kit look expensive but I don't think I could have got it done for less than £30
I also have an old Suzuki Grand Vitara which was not blowing as cool as it should be so I gave this a blast of gas as well and now its cold again and I still have some gas left. Sometimes with an old car its not worth spending a lot of money fixing a small leak, if it lasts 24 months I will be happy. So that makes it look a bit better value for money.

I think nearly every post has been negative which maybe indicates its not a job to be done at home, but I would do it again It really is simple and safe if you follow the instructions. Shame we have no input from other people that have done it themselves

IMHOI would recommend it, especially if you have an older car that is not worth much.

Thanks everybody for such great input