I bought all that equipment a few years ago.  It has more than paid for itself.  I didn't know Autozone loaned those out.  

This is old BS put out by DuPont(who held the patent on r12). It can be mixed.

My ASE cert ran out years ago I don't have any of that documentation anymore.



Asking car stuff on arfcom is like asking gun stuff on Pinterest

To recharge your car's A/C you really need to watch the high pressure side.  The gauges on those single hose/can recharge kits are low side.  And since either the low pressure switch (orifice system) or TXV will do its best to regulate the evaporator pressure, the low side pressure will only show if you have a gross under or over charge.

You can find gauge sets at auto stores, and Harbor Freight puts them on sale for ~$50 - I've used them and they work just fine.  Probably one of the best deals are these for $58 -
https://www.amazon.com/Mountain-8205-R-134a-Manifold-Couplers/dp/B000JFHNG0/
I have these and they are very high quality.  They will attach directly to your car's fittings and the R134a can tap.

If you're using a vacuum pump, you'll need this adapter -
https://www.amazon.com/FJC-6014-Vacuum-Pump-Adapter/dp/B0002JMF98/
(Automotive R134a systems use a 1/2" Acme thread, and the vacuum pump has 1/4" SAE flare.)

While you're ordering from Amazon, get one of these thermometers, too.
https://www.amazon.com/Interdynamics-TH-27-Automotive-Thermometer-Refrigerant/dp/B002G1PBHI/

When recharging, you're looking for a high side pressure that is 3 to 3.2 times the ambient temperature.  Example, the thermometer says it's 90°F outside, so you're looking for 270-288 psi.  Don't get hung up on little numbers, and too low is better than too high.  so you fill it until the high side says somewhere around 260-275 psi and you're GTG!  When you're done, open the windows, turn the fan to medium, and stick the thermometer into the dash vent to read the temp of the blown in air.  50° or less is great.

You criticize everyone yet your own posts are completely free of any useful information.  Why don't you post your own tips and tricks?


ETA:  This chart came from an Interdynamics A/C recharge kit.  As you can see, the high side pressure lines up very well with my 3-3.2x rule of thumb.

I just get in the manual, and charge the weight it says the system needs...

Mine was actually over pressure when it got to around 110 degrees this year.

For a car you are supposed to fill to a specified weight of refrigerant.  For a car that is converted over to 134, or a modified system, this won't work.

Sounds like this thread is filled with mechanics and hvac guys.

Yes op, its pretty easy. You can watch a youtube video on it and figure it out. No need to hire a pro unless it has a leak that you cant find and have exhausted all youtube options. It wont be perfect but if it cools then who cares.

*licensed class a combined hvac/r contractor who works on chillers up to 300 tons.

Just wait until you figure out the markup they get for selling it in those special cans. It was like 800% last i recall.

In my experience, cars are pretty forgiving compared to a big system. Ive seen guys in a pinch, fill them until the compressor rattles, bleed off a bit and call it good.

Check the cabin air filter if all else checks out ok.

Most manuals say once a year 12-15k miles, my AC ran like hell (heat in the winter wasn't much better)....changed out the air filter, it was packed full of dirt, lint, etc.....everything ran great afterwards.

Those charts can be a guideline but are not the be all end all. What type of system is it? Orifice tube or expansion valve? Some of the newer systems have some kids on the compressors to control displacement/output. What rpm is the engine running? What is the humidity? Is the blower on low or high? Are the evaporator and condenser completely clean and is there adequate airflow across the condenser? Where are the low and high side fittings in relation to the compressor? Right at the compressor gives you very different readings than if they were on the inlet and outlet sides of the orifice tube or expansion valve. I've seen it.

Every one of those things will affect what normal or correct low and high side pressure is for any given system.

The only guidelines that are pretty solid are the temperature drop recommendations. 90f ambient air temp and vent temp should be 30f+ lower. The lower the ambient temp the less differential is expected. 50f is about the coldest vent temp you can expect from most I've seen. Yes some do a little better, down to about 40f but then you start having issues with evaporators freezing up.

I redid the entire a/c system in my 01 Jetta last summer. I didn't have a scale at the time and was charging from a 30lb jug so i was going to go by pressures. I was getting vent temps in the low 40s at idle but had about 50/140psi. The systems I see at work will be 15/210psi under similar conditions. One size fits all does not work on mobile a/c systems.

Blah, blah, blah.  ZERO helpful or useful information.  Can you do anything but criticize?  Apparently not.





So that's your helpful advice - take it to a mechanic so he can weigh the charge.  Again, ZERO helpful or useful information.

The OP didn't title this thread "Is it hard to take your car to a mechanic so he recover the refrigerant, weigh it, and recharge to manufacture spec?"  No.  Go back and read the title again. We're talking about a guy standing in his own driveway with the hood of his car up, squishing a $10 can of refrigerant in so his system will cool and he can avoid getting ass-raped by crooks in the automotive field who want to grossly overcharge for making a simple procedure seem mysterious and difficult.  It isn't rocket science.  It's just opening a valve on a can and pumping some gas into a system that has a fairly wide operating margin thanks to the accumulator/receiver that acts as a reservoir to hold unused/excess refrigerant.

That's what we're talking about here - do it yourself.  Not bending over for some repair shop high school drop out who wants a hundreds of dollars to do what the OP can do for $10 at Pep Boys.  And in my experience, my chart and rule of thumb easily gets the charge in the proper operating range with little effort and minimal cost, and without a trip to the scumbag ripoff representative of the automotive field.  But keep selling your bullshit because I'm sure that uninformed customers fall for it every single day.  But not here.

the patent was running out on R12, and the market was starting to get saturated with it. We were selling it at $15 a cylinder. Lo and behold, it comes out that R12 is no longer usable, and will be phased out for R134a, and the time limit is very short. So, we had everybody and their mama trying to get a/c work done if they needed it. Supplies of R12 started dwindling at the end of the switch over period, and overnight the price went to $40 cylinder on a Tuesday or Wednesday. By that Friday, they were $80. The next week I was able to get 4 of them to my garage customers, at $120 cylinder. That last month, it was almost impossible to find R12, and when you did it was $280 a cylinder. It finally got up to about $400 for a 30lb cylinder.

Once the prices of R12 hit $120 and up, we were switching people over to R134a, since it was running about $40 a cylinder at the time. The R134a molecules are much , much smaller than the R12, which makes the R134a more susceptible to leaking not only past the o-rings, but actually through the body R12 hoses themselves. So to switch, you had to change all of the R12 hoses, or it would leak right out. You had to change the hoses and O-rings, the accumulator, drier, filter, pretty much all but the condenser and compressor. You had to reclaim the R12, and then use the machine for R134a and pull vacuum on the new system and charge it.

There was still a problem. The PAG oil that was used for the first few months wasn't compatible, and the R134a would leak out of the system from the O-rings in the hose fittings. Finally, they came out with a second PAG oil that fixed it. Lot's of pissed off customers though, where the system leaked down after a bill for $800 and a month later they had no a/c..It was a mess.

I can remember calling all over the place trying to get refrigerant to sell to the shops in my area. Hell, I drove my personal car 125 miles each way to pick up three 30lb cylinders of R12 I found for about %20 cheaper than we were normally getting them.

Like I said, that changeover was a complete mess.

Yes, they do leak a small amount per year over time. The oil / seals degrade, and it will leak past that at peak pressures on the high side. R134a will actually leak at the fitting on the high side a tad.

LOL.  Do you know what three cans of quick sealant charge shit does to a Tahoe with rear air? I do.

Keep helping people damage their stuff, because when you tap out, I'm the guy that gets called.

NONSENSE...

Over the years the refrigerant will diffuse thru hoses, seals, and the compressor seal..

It's PERFECTLY NORMAL, in many cases to add a pound or so after many years...

I just did our 15 YO SUV 2 weeks ago, see thread in the SF forum...

I suggest getting a small pocket thermometer and sticking it into a dash vent so you get a feel of the correct temperature over time. Only cost a couple $



Handy charging cylinder I had made up in my biz shop, made about 8 of them, years ago for precision filling of small amounts in various systems we had.

Work great for measuring in small amounts in vehicles, airplanes, etc...






SO is carefully purging it...

She knows what she's doing before the weenies worry abt gloves etc...


The refrigerant appears cloudy because of entrained vapor and a little air.

After sitting a while, it becomes clear...

Couldn't find R12 at a reasonable price for my 1990 Miata.

So, after the system was evacuated, I tried R12a (aka: Red Tek). Read and follow the directions, it's not a 1:1 replacement.  It worked.

Aloha, Mark

Go on...

If the system won't hold pressure then it has a leak.

The simple answer is.......Yes, you could DIY.

But, that all being said...........

Be careful not to over fill your system with refrigerant (and/or oil).  You could end up blowing out seals, etc....  Which could end up costing you more $$$.  Yes unfortunately, I've done it.  

Then again, I've also had some success with DIY AC re-fills and some major parts replacement for my car's AC system.

I'm not a pro.  Though I did invest in a HAYNES AC manual and manifold gauge set, prior to my adventures.

LOL.  Will we be arguing about ___XYX Brand 134a refrigerant_____ vs. Wal Mart brand 134a next?   BTW, I saw them yesterday, under $5 a can at Wally World.

Aloha, Mark

Be sure to check the electric cooling fans for the condenser are working when the a/c is turned on.