Ac r134a charge - am i doing some thing wrong?
 

Ok, so i trying to charge my ac system and everything looks ok til take a drive. When i charge i see the air temp go to 10 degree C, bit as soon as i go for a drive they rise to 25c, looking at the gauges when charging, i get arond 25psi low side and arund 220 psi high side when filling at idle rpm, after the drive the low side might show 10 psi and high side maybe 150 psi.

I have pulled vacuum for 4-5 hours, flushed with 2 times with some refrigerant and then filled.

Any one have any suggestions?

Do i Need to fill more?

You should be charging it when RPMs are at 1800.

Did you bleed the air out of the fill line before opening the low side to let the R134a in?

Also, it is best to fill only 80% of R12 capacity chart.

Yes, too much fluid will cause it not to cool.

how much have you put in. (oz's)

put the fan on hi
you need good air flow over the condenser(s)
for 134 you want about 35-40 on the low side.
check pressures at around 1500-2k rpm
depending on how hot it is and how good the air flow on the condensors the hi side can get very hi. 300+

after pulling a vacuum did you close the gauges and turn off the pump and let it sit to see if it holds the vacuum

what is the outside air temp

do you have the old original compressor

whats been done to the system

In 15 years of so of working on auto a/c, I've never charged or checked pressures at anything above idle speed, (all fans and thermostat settings on max, windows up and doors closed), except out of curiosity - works perfectly at idle and no need or benefit to increased engine speed. Butt that said, many techniques work, so it comes down to personal preference.


John, did you charge the system with the engine lid up or down?

i have seen plenty of times when the low side looks good at idle, rev the engine and hold it and it drops too low. this is where the system operates most of the time and you want it filled properly for off idle operation.
i may charge with it at idle but i always rev and hold it to check the final pressure.
also reving can help speed up the charge because it brings the low side down when it comes to getting the last little bit in. (along with putting the can in hot water).

with a good system (i would not do this on a Porsche) you "could" charge the system without gauges. keep the RPM between 1500-2k and fill it until the compressor no longer cycles off and on. (i am not suggesting anyone do this).

I disagree about charging for off idle pressure - you want to charge at idle speed, as that is where the system is most challenged, thus if you target your pressures for above idle speed, they can be much too high at idle where the system spends a lot of time operating (traffic jams, puttering around town, etc).

If you get very low vent temperatures at idle, within acceptable pressure ranges, you will also have very low vent temps above idle - with the added benefit of lessened system pressures.

Regardless if you are checking your charge at idle, at 1.5k or 1.8k rpms,
what the board needs to know is what is the ambient temp (F ing please),
and how much R134a you think you put in the system (ounces) .

Glad your not stating 1.72 and 15.17 bar, however that would be sweet at idle with a perfect charge at 30 C ambient

You could be undercharged, you could have air in the system.

======================================

Ronnie, don't start

^^^

Carbon fines?!?!? :eek:

Thank you for all the answers,

Sorry for the C temps;)

Ambient air was 25c, oppps sorry, 77F;)

It's a nipondenso compressor, the ac system had no charge in it when i got the car so this is first time i try to get it workning. I've changed the drier, before starting.

As for how much, i messed up alittle so i lost track how much. Initially i charged with 43ounces according to a porsche tec bulletin i found (http://www.pcarworkshop.com/images/e/eb/Retrofitting_R134a_A-C_1995_680195.pdf)
I think this was to much as i got quite high readings at idle so i evacuated some, to much, and i forgot to take weight meassure.

But on the good side, I added some refrigerant this evening and vent for a drive, and i got 50f for air temp, and it was stable, so it looks like i maybe was undercharged. I will check this again tomorrow and confirm my gauge readings before and after a drive.

Oh good :D Stay Cool Brother! :cool:

43oz is too much R134A. The 89 930 takes 48oz of R12, not the SC. If I remember correctly it's 38oz then you must reduce for R-134A. 20% reduction?

50F is not bad for a stock SC. Would be better to see temps at 90F ambient.

For what it is worth, I went to Oslo in 1985 on a business trip. I was staying at a hotel near Stortinget. I saw King Olaf get into a Cadillac limousine on a Sunday morning on my one day in Oslo before my two weeks in Arendal. Amazing, I lived in Alaska for five years and never sayw a grizzly (brown) bear but only 20 hours in Norway and I saw the King. Sweet.

Maybe they all ran and hid when they saw ol' Bobasaurous lumbering their way in an inebriated and agitated state?!?!?!?!

Nah. That was the late eighties. I did drink but nowhere near what I consume now.

One beer a day is the rule. I shut it down.

http://forums.pelicanparts.com/uploa...1469662728.jpg

if the system is empty and all you do is replace the dryer, unless you got lucky and it was leaking at the dryer, you still have a leak.

#1 warning you get when buying a car:
AC system was just charged up= it STILL has a leak and will need another charge soon.

I've always charged my system with the doors/windows opened in order to keep the thermostat from shutting down the compressor...:confused:

If the thermostat is calibrated and functioning correctly, and the vent temps and temperature inside the cabin have reduced to the point of cycling off the compressor, then there is no need to keep adding refrigerant.

The technique of charging with the windows and doors closed is part of the "vent temp & pressures, while observing refrigerant weight, method" - you are trying to establish a "real world" operating situation for the a/c (aka: I don't drive around with the windows down and the a/c on, so do not charge the system to function in that manner). I know that plenty of a/c charging instructions, from various sources (including guys that make youtube vids on the subject), say to have windows down, and while that can work, it just doesn't make any sense to do it like that.

An added perk of this charging method is that it is Griffzilla (Kuehl) approved and certified. :)

Sorry for not getting back sooner,

Havent't had the possibility to troubleshoot some more the last days, but got the following measures from the gauges when the car has been sitting for the last week, and after a long drive.

Sitting ac not used in one week: Both high and low side meassured 78psi ambient air 77f

When driving and first starting ac temp is about 50-55f but after 10-15 minutes it rises to about 77-86f. When measuring high and low when i got home. It read on low side 0 psi and high side around 100 psi. Ambien air approx 70f

I think it's still low in refrigererant

And on a side note, King Olav was a good king. And loved by the people. During the oil crissis in 1973 he even took the subway and payed his own fare to go crosscountry skiing.

if you had 10/150 and you now have 0/100 you still have a leak.

did you do anything to fix a leak before you charged it

you also low

Yeah i agree that there might be a leak. however, it might just be my inexperience not meassuring things right. I have dye in the refrigerant and looked around with uv light and cant't see any leaks. I might have to get a sniffer. Any way, I'm doing some other work on the car right now so i can't fire it up, but will try and charge some more as soon as possible and post the results and I'll go over the system again and see If i find any leaks.

I'll get back soon:)