AC Gas (R134a)

[toyota62]

Hi.
Do I need to add any PAG oil (ND8 I think this is PAG 46)
If I evacuate and recharge an AC system?
Apart from little low cooling the AC system in good working order.
(With Robin Recovery/Recycling Machine)

 

[Schmoe]

Just add the freon, no need to totally evacuate the system unless your repairing a leak or something like that. Make sure that you get PURE product, and not that [censored] that has some sort of stop leak in it.

 

[Chris142]

I pull the tube to see if it needs oil. If the car uses an expansion valve then that won't work. Look around it. Do you see any dirt or oil at any connections? If it's clean your probly ok to charge it w/o adding any oil.

I usually add a few ounces of oil just to be sure. A extra ounce or 2 of oil won't hurt the cooling any.

The proper way to charge it is to evacuate it and charge into a vacuum with a scale. Shooting it up w/o knowing how much is still in it is just guess work.

 

[mechtech2]

If the system is not empty, an evacuate is not needed.
If you KNOW that water is in there, go ahead.
Add oil if you know it is leaking. No evidence = no oil added.

 

[toyota62]

If I evacuated the system then I have to add some oil right?
Camry service manual doesn't say to add oil.Only if replace condenser,evaporator core or Ac compressor to add oil.

 

[mechtech2]

PM'd.

But for others, if the system has not been opened for repairs or from damage, no oil is usually needed . If there was any residual charge of 134a, no water will be admitted .

 

[swalve]

Just curious, if the system was leaking on the low side, wouldn't the action of the compressor pulling a partial vacuum before the low limit switch shuts it off cause some infiltration of air/water?

 

[Virtuoso]

There is still pressure in the low side during operation.

 

[mechtech2]

Right. The low side has a minimum of 20 lbs pressure in it.
It is not a vacuum, just lower pressure than the high side.

After a rest, the low and high are the same. Look for about 80 with the car off, and sitting overnight.

 

[mechanicx]

Generally oil is not lost unless there was a fast and massive leak or you replace parts. If you are just drawing a vaccuum (always a good idea) then recharging, normally you would not need to add oil.