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same temp evap in and outlet

wuntun87 on Tue August 31, 2010 2:11 AM User is offline

Year: 1999
Make: chevrolet
Model: camaro
Engine Size: 3.8
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 45
Pressure High: 210
Country of Origin: United States

i am in need of help on this one. the lowest temp thru vents is 68* and the evap inlet is 58* and outlet (suction) is 69* or almost the same..... about the same temp all the way to the drier/accum. from there ..what could be causing this? it had symptoms of a low charge and after finding no leaks, added 1/3 can and the cycling stopped then pressures stabilized at 30 and 175....... vent temp was 71* at that point so i added couple more ounces..... pressures went to 35 and 200... vent temp 70* ...... added couple more ounces made 45 and 210 and the vent temp now has only dropped to 68???? im at a loss as to why it wont cool properly. anybody have a suggestion? thanks in advance..

bohica2xo on Tue August 31, 2010 2:31 AM User is offline

You are in charge La-La land. You added "some" to a system that was "low", but had "no leaks". You have no idea what the actual charge is.

You have a 12 year old car that is low on refrigerant. It has a leak someplace, the charge faries did not come borrow some refrigerant.

You could be on the money with the charge right now, but have a worn out compressor. You could be way undercharged with a bad fan clutch. No way to tell.

Best bet is to recover the system, open it and add back 1.5 ounces of oil and .25 ounces of dye. Pull a vacuum, and charge the full charge by weight. Then begin testing pressures to further diagnose the system. Work from there.


"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.

wuntun87 on Tue August 31, 2010 3:29 AM User is offline

thanks for the reply bo. i agree with you on the unknown charge amount, but i didnt want to recover and replace just the charge without figuring if i need an orfice or dryer/accum. or clogged condenser???..... with taking the charge press. from 30/175 to 45/210 i would expect more than a 3* temp drop in the vents...this system has never been worked on so i suspect the leak was very slow and thru the hoses rubber... couldnt find any signs of leaking at all, and sniffer couldnt find any either..... i see your points but this car only has 65000 miles... and no clutch fan but electric and working fans.... i would expect to get in the 50's or even 40's with this at 85 degrees... daughters car and just tryin to get her another couple months of a/c then shes trading up......Are there any more tests to try to find specific fault with above mentioned parts?

HECAT on Tue August 31, 2010 6:38 AM User is offline

There is a difference in what you want to do and what you need to do. You cannot diagnose or perform any tests with pressures or temperatures without first covering the basics. Recover (good time to inspect O-tube), vacuum, and recharge with full spec.

I suspect low charge causing oil to pool in evap. but this may have already occurred, starved the compressor for oil, and it has already failed. OT inspection would help ID if this has or has not occurred.

You can just keep adding refrigerant if you want, it will either get cooler or fail.


HECAT: You support the Forum when you consider for your a/c parts.


iceman2555 on Tue August 31, 2010 11:03 PM User is offlineView users profile

The evap temps are NOT within spec's. Ideally they will be the exact same temp. This temp range indicates a undercharged system. We are back to the 'superheat' issue once more. This system has liquid/vapor inlet charge and a true gaseous outlet charge. There are several issue that are going to result in some serious cash outlay...if they have not already occurred.
The compressor on this vehicle is a variable displacement unit. When the low pressures drops below a set point, the compressor reacts by allowing discharge gases into the compressor cavity to adjust compressor size/work load ability. When this condition is occurring the lube flow to the compressor may stop or be greatly reduced. The lube flow will not resume until the suction pressure reach a set point and then the control valve will allow for release of the discharge gases and allow suction side operation....then lube flow will resume. This is a serious issue...not so much that immediate compressor failure will occur, but there exist within this compressor a bronze bearing surface...this is the first area of damage....the result is the same...the compressor is going to fail.
This vehicle also has another very unique characteristic...the condenser flows in the reverse direction and they become easily restricted.
Get the system charged properly PDQ or expect to spend large quantities of cash.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

wuntun87 on Wed September 01, 2010 12:24 AM User is offline

thanks for the input ppl. you know i completely forgot that inlet and outlet temps should be close to the same...... guess i had a brain freeze with the non-desirable temps overall. I will go ahead with your suggestions as said.... like the commercial used to say .."you can pay me now or pay more later" .... What online store has the best a/c parts for the money and shipping rate? thanks to all who answered....

jglanham on Wed September 01, 2010 12:42 AM User is offline

What online store has the best a/c parts for the money and shipping rate? thanks to all who answered....

The site that sponsors this forum!


wuntun87 on Wed September 01, 2010 1:12 AM User is offline

forgot to add: is the variable orifice worth the money? ( $2 for o-tube and $40 for variable)

iceman2555 on Wed September 01, 2010 8:13 AM User is offlineView users profile

NO !!!!!

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

wuntun87 on Sat September 04, 2010 12:43 AM User is offline

just to refresh, this is for a 1999 camaro. thanks to all for the input. i replaced the accum. and o-tube ... vacuumed down system, purged with nitrogen, pressurized with nitrogen to 225 psi, checked for leaks, left on over night, alls well and gave the system a fresh vac down to 29" for 2 hours. NOW the funny stuff happens. (again!!!! ) ambient temp 96* add 2 oz. oil and 12 oz 134a engine idle - max fan - recirc mode - closed cabin low 40......... high 225....... vent 71* add remaining required refrigerant of 12 oz. and allow to stabilize 20 min. now @ recommended charge low 45.........high 250........vent 71* (that is correct, same temp as half charge, and the heater door is not open) rpm test at 1500 rpm low 40.........high 275........ vent 69* add a giant fan in front of vehicle low 35 ........high 225........ vent 67* (doors open fan high or low don't matter gives 74* thru the vent) physics say i should be waaaaay colder than this (and the degree scale on the gauge)........ but look at the over all picture here..... half a charge to a full charge to 1500 rpm to a simulated road test and all i get is a lousy FOUR DEGREE difference...... and this thing SHOULD BE in the 50s* at this psi..... sooooooo please help and tell me what kind of Fahrenheit fairy is stealing the degrees from this possessed car. thanks >>>>>>>>>>>>>

Edited: Sat September 04, 2010 at 12:57 AM by wuntun87

wuntun87 on Sun September 05, 2010 12:59 AM User is offline


NickD on Sun September 05, 2010 9:48 AM User is offline

Originally posted by: wuntun87
forgot to add: is the variable orifice worth the money? ( $2 for o-tube and $40 for variable)

Are you saying you added a variable orifice to a V5 variable displacement compressor? If you did, your compressor doesn't know if it is coming or going.

If you want answers, need to provide a lot more history. And yes, it is not easy to charge by pressures with a variable displacement compressor. Bohica told you this right from the beginning, but you are ignoring him.

wuntun87 on Wed September 08, 2010 3:38 AM User is offline

i did not use the variable orfice... charged by weight not pressure. charged exactly recommended 1.5 he had said to do, as to not be in limbo with amount in system. i still have a good pressure that should give a good evep temp, but i cannot achieve this. i am totally at another reason for this to occur. what other info is needed for more diagnosis? thanks.

iceman2555 on Wed September 08, 2010 4:26 PM User is offlineView users profile

I am a bit perplexed exactly how the system was charged by weight when 12 oz cans are utilized! Once unique characteristic of the variable is that it will maintain certain pressure ranges and still be operating in 'destroked' condition. This system is one of those, it needs to be charged by weight by the proper and correct procedure.....a recharge machine or the use of scales and a correct weight. Another issue could be the recharge method, were your charging hoses pre charged or was the extra amount of refrigerant required taken into consideration with your 'calibrated' weight. Normal primary charge for a standard manifold with 62 in hoses is app 4 oz. This alone could be an issue.
Also the evap inlet/outlet works best with a highly heat saturated evaporator....OPEN THE DOORS! This will insure complete flooding of the evap under extreme conditions.
The best procedure would be to have the system charged correctly by someone with the correct equipment.
Also, is this a simple service procedure or is this part of a system repair...compressor etc?

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

NickD on Wed September 08, 2010 7:26 PM User is offline

V-5's control valves have been known to go haywire, think that is another word for being broken. Since I never had a reason to take one apart, will leave that to someone that does.

Also noted, not very cold vent temps when the ambient is low, but sure kicks out ice cold air when it hot outside. Makes me wonder why my car even has an AC compressor switch on it. Bypassed in Recir or defrost mode, and with that minimum cooling, just running the compressor for nothing and wearing it out. Been meaning to disable that feature, but have to pull the entire dash apart to do that.

Also hate cans with a passion, they have to be purged with each change, so how to you precisely measure that?

wuntun87 on Thu September 09, 2010 1:22 AM User is offline

Thank you iceman and nick.....Well, my 30# ran out last year, and i haven't seen the need to purchase another, since i don't do a/c work for a living, i cannot justify keeping that much around. It will last me 10 years like the last one!(i do all my own a/c work, auto and home and refrigerator.) If the price falls this winter, i will buy another 30#. But for now just 12 oz. at a time for me. As for accuracy? i use a refrigerant scale, and it does work with the 12 oz. cans, to the hundredth of an oz. (zero it out and i "watch" the ounce's go in!!, all 12) Just for my own peace of mind, about 5 years ago i added 2 small valves and another "tee" to the center charging port "tee".... so when i purge with nitrogen, vacuum, and charge, i never have to break any lines! I never have measured how much will be "left" in the gauge set, so you have a very good point. Did a full test again, adding 6 oz. and it got hotter with every ounce. Bled 6 and it was back to what it was to start. my daughter gets home last night, i decided to run another test since ambient was much lower at 85* ...... so
ambient 85*, car @operating temp
low 35 / high 225 / vent 65
raise rpm to 1800
low 30 / high 250 / vent 62
add fan in front of car to simulate driving conditions, and continue 1800 rpm
low 29 / high 220 / vent 59
well, now we have a total of 26* under ambient, but, this is with windows up and recirculate on. (open doors and vent goes from the 59* to 71* and holds at 71* and outdoor humidity is 78%)................ Is this as good as it gets? I don't have a bench-mark to go by because i have never needed to put a set of gauges on this car before it quit cooling, or a thermometer in the vent.ft> i just know that it is definitely not as cool as before. its a huge difference, i would guess 15 degrees or so. Well, are there any other things i can do or check or is this gonna be an all out R&R of the condenser and or evap and or compressor? thanks

Chick on Thu September 09, 2010 7:09 AM User is offlineView users profile

Is the return line back to the compressor (Suction line) cold?? If it is, you have heat blending in with the evaporator air..If it's not cold, post back and we'll go from there...

Email: Chick


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NickD on Thu September 09, 2010 7:13 AM User is offline

With those pressures and that poor cooling, and assuming everything else is clean and good, you are telling me you introduced air into the system.

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