Air Conditioning Performance Improvement

[kylemorg]

Since I got my '02 XD GT, I could feel the A/C cycling on and off; alternating cool and warm air would come from the vents. Upon further testing, it appears that the A/C system is overcharged with refrigerant. I got a pressure gauge/filler tube setup recently and checked the pressure on the "Low" side of the A/C system (while the car is running, as you're supposed to).

So, to remedy the situation, I let out a bit of the refrigerant from the "High" side of the A/C system:

Supplies: small screwdriver, paper towels, A/C system pressure valve, R134A refrigerant or refrigerant/lube/sealant.


First of all, I'd recommend wearing safety glasses while doing this; high pressure gas and oil will come out of the system when you vent it.
Open the hood
Remove the light green "L" cap from the aluminum A/C line between the belts of the engine and the firewall. Be sure not to get any dirt in the valve.
Hook the pressure gauge to the "L" valve.
Start the car.
Turn on the A/C.
Check the gauge on the low side to see if the pressure is within the minimum and maximum (usually marked green) range on the gauge. If it's within the range, you're finished. If it's below the range, add more refrigerant or lube/refrigerant/sealant. If it's too high, proceed with the steps outlined below.
Find the light green cap marked "H" on the aluminum A/C lines to the passenger's side of the engine.
Remove the cap, but be sure not to get dirt inside the stem (similar to a tire valve stem) beneath the cap. Do not drop the cap and make sure you don't come in contact with any of the moving belts or pulleys on the engine.
While covering the hole with a paper towel, gently press down on the valve inside the stem with a small screwdriver or other tool while keeping your face away from the top of the valve. The paper towel is there to block the oil that will come out. The gas will come out at high pressure, and is a potential problem if you inhale too much of it, so use caution!
Vent the system for ~1 to 2 seconds.
Allow the system to re-equilibrate (~1-2 minutes).
Check the gauge on the low side again.
Repeat the venting steps as necessary until the pressure comes down to within the proper operating range shown on the gauge.
If you vent too much, refill the system from the low side with R134A approved refrigerant.


If you're concerned about venting off a bit of refrigerant, you can take the car to an A/C service place and have them collect the refrigerant for you.

I'll add pictures at a later date.

[Kenshin]

Good looking out! Thanks for the tip!

[felixr]

uhm it seems this is a problem specific to your car. i may be being ignorant here but im pretty sure my 01 wasn't/isn't overcharged. "underblown" sure but it doesnt alternate warm and cold air. . . is it just me? . . . . is it just YOU?

[redgum]

my 2002 only blows cold air when set on cold...

[felixr]

my hot/cold selector knob is broken(i think)and my a/c ONLY blows cold air 90% of the time. sometimes, if im real lucky, it blows steaming hot air on a nice hot miami summer day!!!

[Leviathant]

In my 01 GLS I can hear the AC cycling, in a way. It's never blowing warm air when turned to cold, for instance, but it does definitely cycle. I try to avoid using my A/C and conserve on the gas (back up to $2.05 a gallon again, hooray! Hey, when I was in California last month, it was $2.65-$2.75 a gallon. Ouch!) Interesting find though, kyle. Any bad side effects to running with less refrigerant?

[southpawboston]

interesting thread.

last year, i noticed my A/C would cycle very often, and i'd also get a "whistling", very faint, through the vents each time the compressor would kick in. sometime between last summer and this spring, my A/C condensor got punctured by a flying pebble. i had to replace the condensor ($600...OUCH!). this year, i noticed the A/C does not cycle nearly as often, and puts out a consistently nice cool flow of air. and the whistling is a lot more faint, almost non-existant. i'm wondering if the pressure in the old system (before replacing the condensor) was too high???

my next question is, why would the pressure EVER be too high??? shouldn't it be tested each time it's recharged?

[ricerrx7]

Discharging refridgerant to the atmosphere is very illegal! Also, you have to measure both the high and low sides to get an accurate diagnosis of what's going on.
And Southpaw, the cycling would indicate low pressure.

[kylemorg]

There is also a pressure sensor on the high side that will stop the compressor; from what I undersatand from an auto tech friend, it will stop the compressor if the pressure on the high side is too high or too low.

A pressure test of both sides is a good idea to make sure the orifice isn't plugged; however, I haven't seen any high-side A/C pressure gauge systems at the local auto parts places.

Yes, you should collect the refrigerant; you can do it with an evacuated collection cylinder for recycling, which is what I'm going to do next time. ;)

[BlackElantraGT]

Discharging refridgerant to the atmosphere is very illegal! Also, you have to measure both the high and low sides to get an accurate diagnosis of what's going on.
And Southpaw, the cycling would indicate low pressure.

Doesn't that only apply to freon? That's why most manufacturers switched to R134a refrigerant right?

Recently I also purchased one of these kits with the guage and refigerant. The girl at walmart scanned the UPC for the refigerant, instead of the kit (which was somewhat hidden underneath), so it came out to a little over $10, when it probably should have rang up closer to $30 something bucks.

I decided to do this because while in Vegas the a/c just wasn't getting cold enough. It turns out that I didn't need any refigerant, I guess it was just that hot in Vegas.

[ricerrx7]

R-134a is just as bad, if not worse than R-12 (just in a different way) but they have just recently discovered that. DO NOT TOUCH YOUR A/C SYSTEM IF YOU ARE NOT EPA-609 CERTIFIED! That is a big no no.
And kylemorg, no they do not sell these high side guages at most stores, but that doesn't mean you don't need to test it. If you don't look at both sides, you CANNOT tell what's going on in the system. If you're low side pressure is too low, then you might assume that there is too little refridgerant in the system, but if you hooked up a high-side guage and saw high pressure there, then you would realize that you have a restriction somewhere in the system.

[felixr]

kinda on topic, kinda off topic . . . for those people that live in really hot areas like me
have you ever noticed that you have the air on full blast but its so hot the radiating heat from the metal in the roof and through the windshield is still burning like your face and head while your right cheek is ice cold? man i wish our cars had better circulation and more blower power. its almost as if hyundai said: "well so long as it at least comes out of the vent . . . thats all they need"??

[kylemorg]

FelixR -- three words: Metalized window tint.

As for adjusting the pressure in your A/C system, if it gets too low, you can always top it off with the DIY R134 kits available at any auto parts store. I notice a HUGE improvement now that I've lowered the pressure in my A/C system; the vent system always blows cold air now, regardless of engine RPM (although it still gets a little bit cooler when the RPM gets up around 2-3K due to the increase in A/C compressor pump speed).

As for the R134 refrigerant leaking out; my wife's A/C system lost so much of the R134 that it didn't register at all on the low side gauge, so there's a whole system charge's worth of R134 (maybe 500 g in a system?) in the atmosphere from her car due to a leak. So how is my car "losing" a few grams or so any worse than that? Also, I'm sure lots of cars involved in wrecks lose their refrigerant. It's not like I'm advocating that everyone with an air conditioned car in America vent out all of their R134 into the atmosphere...

Also, if you have any discomfort doing any of this, don't do it -- go to a professional A/C shop. All I'm saying is that this entirely solved my personal A/C problems specific to my 2002 XD, VIN KMHDNXXXXXXX; it's your choice if you want to try it or not. I make no claims that this will work for you or that it won't damage your A/C system.

[sed]

you could always get an underdrive pulley made for the compressor, making it spin faster

[felixr]

Would this help in blowing more air out or would this simply make the air colder? any colder and i'll grow icicles but only on my right cheek cause the right middle vent is the strongest of all vents. the other ones are (i swear) just barely spit out a light breeze as if you are gently blowing your breath at someone. so sad

[sed]

make it blow harder

shawn :)

[felixr]

in the ace ventura voice: "reeeeheeeeeheeeheeeeheeeeaAAAAAlllllleeeeeeeeee . . . ."

[Leviathant]

Let's see a DIY for that! That would also probably get some air blowing out the vents under the driver & passenger seats, for the rear passengers.

Hehe, I was also thinking of routing some of that ventilation on to my Hyundai/Clarion head unit, because I don't think it gets enough ventilation, given that I have a multigauge sitting on top of it. CDs get reeeaaally hot. The thing is, I'd have to have some way to turn it off for the wintertime when I'm blowing hot air. Too much engineering!

[CodyTheBowler]

ahh i feel you about the lack of pressure. i live in vegas, and last week it was about 100 degrees out (cooled off for the last time this week yay), and my dark grey interior is just a giant solar panel for heat. what i found that works is turning the recirculator thing on, and blasting that sucker at level 4 with the windows open a crack. it helps circulate the air while keeping moisture (<10% humidity here) in my sensative nose. any aftermarket products to blow air harder? (a supercharger for your fan :-D?)

[BlackElantraGT]

ahh i feel you about the lack of pressure. i live in vegas, and last week it was about 100 degrees out (cooled off for the last time this week yay), and my dark grey interior is just a giant solar panel for heat. what i found that works is turning the recirculator thing on, and blasting that sucker at level 4 with the windows open a crack. it helps circulate the air while keeping moisture (<10% humidity here) in my sensative nose. any aftermarket products to blow air harder? (a supercharger for your fan :-D?)

I feel you on that one man. I got there on the 21st of May and I swore it still felt like more than 100 degrees at night. Good thing it cooled off a little day by day after that. I used to live in Fresno and dealt with some pretty hot weather, but I must say it's nothing like Vegas HOT.

[ricerrx7]

Also, if you have any discomfort doing any of this, don't do it -- go to a professional A/C shop. All I'm saying is that this entirely solved my personal A/C problems specific to my 2002 XD, VIN KMHDNXXXXXXX; it's your choice if you want to try it or not. I make no claims that this will work for you or that it won't damage your A/C system.

I'm not uncomfortable working on HVAC systems, I am EPA 609 certified to work on them. And you are correct, you aren't letting out as much as if you were in an accident, but what you are doing is intentional which is illegal. You won't get fined for polluting if you are in an accident, but you will for doing it on purpose.

[taylors5]

So I have an 02 elantra and my a/c definitely cycles very often. When it is on it is very cold and then you get warmer air and then it cycles on again. It happens even when it is plenty hot and engine speed does not seem to change anything. Is this normal?