A/C car correct charge mode

[Acrisoft]

Which is the best way ?
Load R134 with a scale or charge R134 in gas state
by suction line with compressor ON ?


Moises

[Shibhrac]

It's better if you do them both in the same time. If you know the required quantity of refrigerant you can charge it in vapour state .

[Acrisoft]

If a guy does not have a scale or the weight is unknown, can he charge by suction line until obtain 30 or 40PSI by the low side ?

Or he will never be sucessful without knowing the amount of refrigerant needed ?

[lowcool]

charge by liquid it does have fractionation

[Shibhrac]

You could manage to charge the system with the required amount of refrigerant by monitoring the pressure readings and sight glass.

[Clk320_Greg]

I thought you had to charge 134A in liquid?

[monkey spanners]

R134a is not a blend, its a single component refrigerant.

Blends have a capital letter after the refrigerant number e.g. R404A, R407C the futher along the alphabet the worse the glide so R407D would have a worse glide than R407C.

The 'a' after R134 should be in lower case, as its left over from when the gas companies were develpoing it, presumable there were b,c,d etc versions that didn't make it into production.

So you can charge it as a vapour or liquid to suit your requiremnets.

Jon

[Grizzly]

R134a is not a blend, its a single component refrigerant.

Blends have a capital letter after the refrigerant number e.g. R404A, R407C the futher along the alphabet the worse the glide so R407D would have a worse glide than R407C.

The 'a' after R134 should be in lower case, as its left over from when the gas companies were develpoing it, presumable there were b,c,d etc versions that didn't make it into production.

So you can charge it as a vapour or liquid to suit your requiremnets.

Jon

Thanks for that info John.
I did not know that.
Added to your rep!
Sorry obviously I like your posts because the system won't let me add to your rep.
Gotta spread a little more love around first!
Steve

[Acrisoft]

In case of a fixed orifice tube with unknow weight. Could I try a R134 charge by superheat ?

[Voyager]

What car are you charging ?

[tbirdtbird]

Usually charge car A/C from low side, no need to use hi side. In fact some makes do not even have a hi side fitting. Not necessary to know the amount per factory. Vacuum, charge slowly until low is about 30 psi. 30 psi is about right for ambients of 80-90*F or so. Brazil might be hotter. It should take you about 15-20 min to allow everything to equilibrate, go slowly. I know a guy who charged to 35 psi at 80*F then went out west where ambient was 90-100 and he ended up actually with overcharge and slugged the compressor.

Be sure windows are down, A/C is on max cool, fan on Hi, and you are not on recirculate. You want the compressor and orifice working at max to charge properly, and the hotter the day the better. These readings are with the condensor fan OFF, else you'll overcharge.

About 30 psi and the suction line ice cold should do it. I pay very little attention to the sight glass.

Then, you won't feel the full effect of the A/C until after you close up the vehicle and drive down the road with some engine RPM up past idle. R134 takes a little longer to get as cold as R-12 did.

good luck, go slowly.

[Voyager]

If the car was originally filled with R134a, not retro-fitted from R12, there should be a sticker/label under the hood specifying the correct charge weight.

If it is an R12/R134a retro-fit, charge with about 80% of the R12 weight.

Also, how much oil is in the system?
If you had a leak, or replaced a component, you will have lost oil as well.

Retro-fitting from R12 to R134a requires the system to be flushed clean to remove the old mineral oil which is not compatible with R134a. The mineral oil has to be replaced with PAG oil.

[Acrisoft]

These are very important information

Most guys here only knows how to charge by known weight. It will be good to teach them they can charge by pressure, especially small repair center

Moises

[tbirdtbird]

U can also use POE (ester) oil with 134. BTW I have never seen a tech use superheat or subcool to charge car A/C. It is just not that hard to do. U can use brake cleaner (which is actually R113) to flush, it comes in gallons if U are converting from R12, but I doubt there are many conversions left at this point in time.

[Acrisoft]

Sorry but English is not my native language and I would like to understand the full Tbirdtbird's message because it seems very useful for me

I would be very thankful if him or other guy could clarify the two doubts below

1-"About 30 psi and the suction line ice cold should do it "

Does he mean ice will appear on suction line ?

2- He says the condenser fan must be off

Do I have to remove its connection ? Is there enough time to charge the system before the motor temperatura raise to critical levels ?

[tbirdtbird]

1. No ice won't appear on the suction line, it will just feel cold. It will sweat, though, as the ambient humidity condenses on the line.
2. The condenser fan will cycle on and off by itself when you are charging and actually it does this all the time. You take the 30 psi suction line reading when the fan is OFF. When it is ON, the reading will be less, ignore that reading. Do NOT remove the the connection.
3. The engine temperature is of no concern to you
Hope this helps.