Another question on adding refrigerant to A/C

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Greetings all,

My 2003 GS430's Air Conditioner is not as cold as it used to be. The A/C has never been worked on (I am the original owner, with 107K miles). So, I figured the refrigerant might be a little low.

I purchased a decent set of manifold gauges (Thanks to all for the recommendations in another thread I posted), and I have the factory shop manual indicating what the proper pressures should be. But then, in the shop manual, I see something which really surprises me.

In the procedure for adding refrigerant, after connecting the can of R134a refrigerant, and expelling air from the hose, it then says:

"Open the high pressure hand valve and charge refrigerant".

[censored]??!! Is this saying the R134a is entered on the HIGH side, not the LOW side? The next step says,

"When the low pressure gauge indicates 14 psi, close the high pressure hand valve".

So, in two places, it refers to the high pressure valve when adding refrigerant.

Every A/C system I have dealt with, the refrigerant is added to the LOW side. Is there enough pressure in the can of R134a high enough to push the refrigerant into the high side? I always thought there was a danger of the refrigerant can exploding if it was exposed to high side pressure.

Can someone out there confirm that this is the right procedure? Sometimes these shop manuals are translated from Japanese, and errors get introduced during the translation. A/C systems can be really screwed up if done wrong, so I want to be confident of the procedure before I attempt this. Anyone out there re-charged refrigerant on a Lexus?
 
Eddie,

Yes, instructions DID come with the gauge set. It does say in the gauge instructions, the following:

"Follow the manufacturer's recommended specification for the amount of refrigerant to charge in that system. Should it specify to charge the system on the high side, close the low side service valve. Open the refrigerant supply container valve, then open the high side (red label) handknob of the manifold. After the proper amount of refrigerant has been transferred, close the high red label handknob of the manifold, also close the refrigerant supply container valve".

So, the instructions on the manifold gauge set seem to suggest that some manufacturers DO want refrigerant into the high side. I assume that refrigerant should always be added with the engine running, and A/C on, correct? Exposing the R134a can to high side pressure seems dangerous to me...
 
If you add to the high side the engine can't be running. Add Freon to the low side with the engine running.
 
Originally Posted By: CT8
If you add to the high side the engine can't be running. Add Freon to the low side with the engine running.

I always did this in the last 20-25 years, add freon to the low side with engine and A/C running.
 
The AC on my 02 Accord also isn't as cold as it used to be so I think it's time to recharge the factory freon. I thought for a moment I'd do this myself but I've decided I'm going to just leave it to a professional.
 
Chris142 - I suspect you've nailed it, as the section on charging the system comes right after evacuating the system.

Interestingly, though, assuming that's correct, there is no procedure in the manual for adding refrigerant to the low side assuming you're just adding to a system that is simply low. Is it always necessary to completely evacuate a system before adding refrigerant?
 
The only correct way is to empty the system and start from empty using a scale. Just adding refrigerant may work sometimes but you have no idea how much to add.

This goes back to the r12 days when cars had a sight glass and you filled it till the bubbles went away. That won't work with r134a.
 
Adding refrigerant to the hi-side like that is usually after repairs are made and the system is in a vacuum from a vacuum pump and the system off....you get lots of liquid in the system quickly that way....plus the compressor will come on since the low side pressure switch will be activated.......no you do NOT open the hi-side valve with a can hooked to the gauges ever lol.
 
Originally Posted By: DSparks
Adding refrigerant to the hi-side like that is usually after repairs are made and the system is in a vacuum from a vacuum pump and the system off....you get lots of liquid in the system quickly that way....plus the compressor will come on since the low side pressure switch will be activated.......no you do NOT open the hi-side valve with a can hooked to the gauges ever lol.


you could get an excess of gas out thatway though.
 
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