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Charging AC question

MikeL on Sat June 26, 2010 1:07 AM User is offline

Year: 1995
Make: Subaru
Model: Legacy
Refrigerant Type: R134
Country of Origin: United States

I went with my service manual for my car I do have a manifold gauge set.. Anyways the charge starts off with charging with liquid refrigerant in the high side where I had an issue yesterday was my car's system and the can reached equal meaning I had a hard time getting over 105 psi to the required 170-210 psi on the high side the system has a pressure switch meaning it wont turn the system on if the pressure is too low. How can I get the high side up to the required levels?

Chick on Sat June 26, 2010 7:41 AM User is offlineView users profile

You pull a deep vacuum, le the high side pull in as much liquid as it can, then shut the high side valve, start the car, turn the ac on and finish charging thru the LOW side.. Be careful not to have the high side valve open, you can blow up the can...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

MikeL on Sat June 26, 2010 9:00 AM User is offline

question when I pull in the liquid the low and high should be about equal right? my low side still shows a vacuum.. Does this mean I have a blockage or a stuck txv?

MikeL on Sat June 26, 2010 11:10 AM User is offline

I'm thinking a bad expansion valve now?

Briandl79 on Sat June 26, 2010 5:05 PM User is offline

This whole thing is confusing to me. First of all you shouldn't charge through the high side. The only way I can figure it's remotely safe is if the vehicle is off, but if it is you shouldn't be looking for pressure that high, when the vehicle is off the pressure is lower than the 170-210 you are looking for. 170-210 is an operating pressure, not a static pressure. I'm not sure what static should be but it's probably around 100.

As Chick said, you need to connect the gauges on both sides, open them and pull a vacuum. After that close the high side, disconnect the vacuum pump and hook up a can of R134A and purge the charging hose, then fill on the low side, not the high, the high should remain closed after you've pulled a vacuum, as mentioned the high side pressure can blow up the can.

I'm pretty sure you can add a 12oz can with the vehicle off, which means when you start it to add the rest the compressor will come on because the pressure won't be too low.

I don't know what the consensus is on charging with the vehicle off but I'm sure someone can chime in.

Edited: Sat June 26, 2010 at 5:06 PM by Briandl79

TRB on Sat June 26, 2010 5:39 PM User is offlineView users profile

You can't harm the system by adding refrigerant while the system is turned off! We do it all the time with professional charging stations. The reason you don't charge through the high side while the system is running is you will not add refrigerant to the system, but add refrigerant or pressure to the can of refrigerant you are holding or the cylinder. The high side of the system is the discharge side. So never have the high side open when the system is running unless you want a trip to the ER.

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Briandl79 on Sat June 26, 2010 5:51 PM User is offline

So even though I know it's the wrong way to do it, are there any reasons not to charge through the high side when the vehicle is off? Is the pressure cutout located on the high or low side of the system?

TRB on Sat June 26, 2010 6:27 PM User is offlineView users profile

Quote
Originally posted by: Briandl79
So even though I know it's the wrong way to do it, are there any reasons not to charge through the high side when the vehicle is off? Is the pressure cutout located on the high or low side of the system?

Don't think I said it was wrong to add refrigerant through the high side with the vehicle off. Matter of fact I said we do it all the time with the proper charging station.

-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

MikeL on Sat June 26, 2010 7:06 PM User is offline

yeah people have been brainwashed in thinking it's not safe.. it's only not safe if you do it with the car running..

So anyways I will flush out my system on Monday and install the new txv, also charging on the high side on a normal system should cause the system to equalize (show about the same pressure) Mine wont which means something is blocking it

Chick on Sat June 26, 2010 11:06 PM User is offlineView users profile

If your low side is showing vacuum, you have a blockage or the expansion valve is clogged or stuck, check for junk in it, it's possible the drier desiccant let go, if so a full system flush is needed and of course a new drier.. Back to charging, car off, keys out of the ignition, let the vacuum pull liquid thru the highside, then SHUT the high side valve, and start the car, and finish charging thru the low side. it's faster, and it's safe as long as the car it not running.. you don't want to charge liquid refrigerant into the low side, as you might slug the compressor. pressures will rise equally as the refrigerant will flash and gas will go into the low side.. sounds complicated, but it's not...takes about five minutes to fully charge the system that way..Just remember. CAR ENGINE OFF when charging into the high side...running when finishing up thru the low side with high side valve turned fully off...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

MikeL on Sat June 26, 2010 11:27 PM User is offline

well the dryer is brand new and impossible for anything came out of it since no pressure went to it because the pressure switch did not close, and of course I'm not dumb enough to charge the system on the high side with the car running.. anyone who does that needs to stop working on cars...

One thing I was playing with is is a expansion valve I brought from my understand warming the sensing bulb will cause the valve to open right? if I blow into one end no matter what the temp is (ice water or heat) I still hear leakage?

I was unable to use the one I brought because because it did not have a external tube that screws down to one of the lines from the evaporator

The correct one arrives monday

Briandl79 on Sun June 27, 2010 2:32 AM User is offline

So I guess the question is: Are there any benefits to charging through the high side? I know you said you could slug the compressor through the low side but that would only happen if you flipped the can upside down right? I'd imagine the biggest benefit to charging through the low side is you'd never make the mistake of opening the high side while a can is attached to it and the vehicle is on, so in other words as a safety measure.

bohica2xo on Sun June 27, 2010 3:13 AM User is offline

Mike:

Many TXV's pass a small quantity of refrigerant even when "closed". This is not a problem, and can actually help keep the system stable. As long as it passes significantly LESS volume when the bulb is in ice water, you are good to go.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

MikeL on Sun June 27, 2010 5:53 AM User is offline

Quote
Originally posted by: bohica2xo
Mike:



Many TXV's pass a small quantity of refrigerant even when "closed". This is not a problem, and can actually help keep the system stable. As long as it passes significantly LESS volume when the bulb is in ice water, you are good to go.



B.

hmm well it sounded the same when I left the bulb in ice water for 3 min.

MikeL on Mon June 28, 2010 3:39 PM User is offline

question... I don't get it.. So everyone was so hellbent with me charging the low side despite it being off.. So I decided to charge the low side with the car running.. got up to 40 psi.. nothing... 90 psi still no compressor turning on.. high side showed just a little reading yet when I jump it and run it you can hear the expansion valve hissing a little and you see a little movement in the dryer but still not enough...

So lets sum that up!

1> I charged with the low side only with car running and 40 and 90 psi compressor still never turned on without me having to jump it
2> High side had little to no reading when charging the low side.
3> Still have no workable AC

mk378 on Mon June 28, 2010 4:06 PM User is offline

If you have 90 on the high side, compressor should start. Again, stop the engine, and put as much liquid into the high side as it will take (up to the specified charge if possible).

I think it will have a trinary switch on the high side, these usually work as 450 psi: off (high pressure protection). So if you have 90 psi and have to jump the switch, switch is bad.

Edited: Mon June 28, 2010 at 4:07 PM by mk378

MikeL on Mon June 28, 2010 4:29 PM User is offline

well the gauges are showing equal right now.. 100 psi low side and 100 high side.

I still gotta jump the switch and when I do I don't see any fluid moving in the dryer.. just a little droplet that hangs off the sight glass.

MikeL on Mon June 28, 2010 4:57 PM User is offline

Well I take it back.. I just disconnected everything to leave because it's storming out here and I get in the car and try the AC again and the compressor cuts in on it's own without needing to be jumped (I thought I left it in) and it was not.. however it's not really cooling still...

txv is hissing louder now.

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