AC blowing warm

[Brad_C]

Originally Posted By: KrisZ
An AC kit with its cheap gauge has its place and time. "Bring it to the professional" advice is fine and dandy when it's not you own money on the line. And the said "professionals" are not all created equal either.


Go on then, explain to me how you use the "cheap gauge" to measure a system charge on both a TXV based system and a CCOT based system.

Originally Posted By: i_hate_autofraud
In answer to the comments on half full A/C kits that fail to transfer the rest of the refrigerant, there's a fix:

When filling your A/C these kits get cold, very cold inside, that causes the pressure to drop enough that no more refrigerant transfers to the car A/C.


Yes you can warm the can. The right way to do it is with the can inverted so you are bleeding liquid in. You let the liquid flash to gas in your manifold gauge. That stops the evaporation from happening inside the can and therefore stops it getting colder with the consequential pressure drop.

 

[Brad_C]

Originally Posted By: Lubener
Originally Posted By: rooflessVW
I would recommend that all AC work be done by a professional with the proper equipment.


It was a bad idea that companies started making these DIY recharge items available to everyone.


The issue came about from back in the "good old days" of R12. The early R12 systems were based on a TXV and had a receiver-dryer with a sight glass. With R12 you could legitimately put the system under a certain set of conditions and charge it up until the bubbles in the sight glass just went away. R12 and TXV based systems were incredibly forgiving.

Modern systems are designed considerably differently, and because r134a is such a [censored] refrigerant it requires far more liquid in the condenser to achieve the right level of subcooling, and you cant just judge that by luck, so none of those conditions now apply and you can't just "git 'er done" using bubba and his farmhand techniques anymore.

It's actually not harder to do right, but you do need the right tools. To be honest, if you were dealing with an r134a system that did not leak you could accurately charge it with a vacuum pump (to make sure it's dry and free of non-condensibles), some cans of r134a and an accurate set of kitchen scales. You would have to have the system emptied first (which is why in my previous post I recommended a recovery machine).

 

[Brad_C]

Originally Posted By: i_hate_autofraud

Older vintage cars have low pressure A/C systems, suction side pressure while running as low as 20 PSI ! Newer cars are all high pressure with low side running at 100 PSI minimum.


Sorry, I missed this bit in my reply but no, that is seriously incorrect.

An A/C unit works by evaporating refrigerant in the evaporator. The pressure of the gas sets the temperature it evaporates at.

At 20 PSI, r134a evaporates at ~23F. At 100 PSI, r134a evaporates at ~87.6F. Unless it's 120F outside and the temperature coming our of your vents is about 97F, then your low side is not running at 100PSI.

 

[dlundblad]

Originally Posted By: Lubener
Just start putting freon in it without further investigation is foolish.Without gauges and knowledge, you either overcharged it (because of a blend door issue) or it leaked out as fast as you put it in.


To be a bit more clear, my kit had a gauge on it. I am not sure on the accuracy, but I used the kit issue free before as mentioned in my OP.

I didn't foolishly add refrigerant as you're insinuating.

My Jeep is a Laredo with the simple climate control. No blend door issues.

 

[dlundblad]

So at this point, I should get a nice set of high/ low pressure gauges and check the pressure and go from there?

*Anyone have any brand recommendations?