82 vette-Air conditioning system way too cold-Pulling 300 psi on high side-High side lines are just about iceing up-Temperature coming out of vents is about 35 degrees. Any reasons why? Thanks

 

I have no idea... but PLEASE send me the entire system for my 68 Vert in South Carolina.

-W

 

Great reply-I like your sense of humor-I laughed when I read it-Thanks

 

Humor is at it's best when it's mostly true.

I really WOULD like to have your "flawed' AC in my car..... right now..... today.....

-W

 

yeah man u have ac that most would kill for in a c3...stop winging and turn it up.

 

Too cold air temps. can be caused by inadequate air flow across the evaporator. The evaporator is the heat exchanger under the dash that the freon lines attach to. Ck. for blocked blower, ducts, dirty blower wheel or stopped up coil/evaporator. The blower could be turning backwards. Contrary to popular belief this will not cause the air to blow out backwards but just at a diminished volume. Incorrect polarity of blower voltage will cause the blower to turn backwards. Outer edge of blower wheel vanes should turn in the same direction as they are pointed. Air temp should run 45 to 50 degrees. mike...

 

My new mechanic tells me there is a restriction in the system. This is the reason for the very high pressures, iceing of high pressure lines and extremely low temperatures. Tells me I need a new compressor, drier and orifice. He did evacuate and recharge the system.
Prior to this problem the pressure relief valve blew out excess R-134 because another mechanic put in too much R-134 (4 lbs). The system at that time before the relief valve blew was blowing out mildly cool air. That's is why I brought it to a new mechanic.
Any thoughts? Thanks

 

Icing on the liquid line normally occurs at the point of the restriction. Liquid line runs from the condenser, in front of the radiator, to the evaporator, under the dash. He may recommend the new compressor to go along with the drier and orifice/metering device to guarantee an operable system. Can be really hard to diagnose properly over the computer. mike...

 

You new mechanic is using the "shotgun method" of troubleshooting.

"Replace everything and we're bound to get it!"

Try the drier and orifice first.

-W

 

I ran an a/c residential bidness for 13 years. If the hi side is 300 psi, you either have 1. too much ref. in the system 2. the expansion device is plugged/plugging. 3. there is a restriction in the hi side.Is there a drier on the hi side, if so, replace it.
The evaporator exit air temp should be NO LOWER than 40 degrees. Sounds to me you have TOO MUCH ref in the system with 300 on the hi side. Try to remove some in 1/4 pound increments to achieve that temp. Remeber you MUST recover the ref., do not blow to atomsphere.

 

I wish that I have the same problem here in Bahrain!

 

to the origional o.p. YOU SUCK!!!!!!

 

This is a first.

 

Your cold man , it was hot here today !

 

Question for you.....(Sorry to the OP for the thread jack)

Today I experienced something similar to the OP...... I have a vintage air kit and it works awesome....actually, it works TOO well because after about 30 mins of run time on the coldest settings, it seems to be freezing up the evaporator....or at least thats what I think its doing....the vent temps start to warm up AND soon there after the air flow decreases BIG TIME.....about 10 mins into the freeze up....I can actually get almost no air coming out even with the blower on high.... So I took to the AC guy that charged the system and is a Certified VA dealer/installer, he said to keep the fan speed on medium to prevent freezing....... WELL today it froze again.... I was getting 37-40* vent temps on average....then about 30 mins in, I started getting 36* and even touched 35* once....soon after it started warming up and struggling to break under 45* and the air flow volume was dying.....

Originally, the system was filled with the exact amount of required R134 and the pressures were in the 150h/14L range.....I thought this was extremely low for the low side but the local VA dealer said that its correct....When I brought it back after the first time it froze up, pressures were the same...

Does this sound like too much or not enough freon causing low pressure and freeze up?


I am calling VA on tuesday but I value opinions of real AC guys......Personally I think the system is low but.....I am no AC guy by any stretch...

 

Your system is not charged correctly, it is low on refrigerant. Normal operating pressures are 40-45 low and 190-210 hi side depending on ambient temps.
At 14 psi on the low side, my gm vehicles will NOT cycle back on without jumping the switch. The low pressure switch is also a low temperature switch.
Study the characteristics of refrigerants: the LOWER the pressure, the LOWER the temp. Your low side (evaporator)refrig temp is very ,very low at that pressure. Increase the pressure to increase the temp-add more 134a-
The FIRST symptom of a low refrig.charge on ANY system is an icing evaporator -vehicle or residential (unless an exotic refrig.is used such as ammonia,etc.)
Icing on an evaporator can also be accomplished by low /no fan speed since you are not APPLYING HEAT to the evap. In other words, start the car after it has sat overnight, a/c off. Start the fan alone- if you have good air flow out the vent, assume your fan is ok. Start the a/c- if it freezes over at the evap, you're short on refrig. Clear as mud?
email me if you need more help.

addedum: All of your symptoms you described could also be caused by the evap. blower that would run/slow/stop intermittedly. So make sure the blower motor isnt on its way out. The low side COULD go extra low & ice over with no blower motor adding heat across the evap.and have the correct refrig charge... Check the blower motor by running it alone for an hour- if it runs correctly, see adding refrig on first note. mikejpss-OUT

 

Well I briefly looked at the vintage air literature and it looks like they are using a thermister and an ecu to control the cycling (assume) and also the blend doors etc. There is also a binary switch (high and low pressure safety switch) on the compressor feed line.

As mikejpss stated, his GM stuff doesn't run at 14psi. I'll add that there are no vehicles running 134 designed to run the compressor at less than 24-28 psi.
Almost all cycling switches from every manufacturer cuts the compressor off at 24-28psi which correlates to approx 32° evaporator temp, and that is done to get the coldest air without freezing. You can check the 134 charts and the specs on cycling switches.

I obviously can't see inside their ecu, it may control the compressor cycling thru the thermister and electronics, but their binery switch (assuming it's safety only and it's a bad place to put a low pressure safety switch, too variable there) should have cut out the compressor long before 14psi and preferrably around 28.

Now what comes first the horse or the cart?
Is it low on refrigerant and freezing above the setpoints or is the low pressure a result of the freezing (predictable) and continued compressor operation.

Here is an interesting tidbit from their instructions



That's just goofy.
Can you imagine spending 70 grand for a new Corvette or Donald Trump in his 30 million retreat in Palm Beach complaining of system freezing and being told "it's normal turn the temp up a bit".


When you call them, ask 2 interesting questions. Seriously interested in their answers.
1 Why doesn't the binary switch cut off to prevent freezing as a safety device?

2 Why isn't the thermister calibrated properly to prevent freezing as a simple temperature control device? (don't let them give you some nonesense about humidity, doesn't enter into it)


As I mentioned a while ago in another post, you can always add a freeze switch in series to the binary or even a real cycling switch (but that would involve a refrigerant tap) if you are truly worried about freezing.

 

I agree with Noonie's observations 100%. I do not have access to Vintage Airs equip., but based on your original comments (above in BOLD type) I still suspect the system was short -charged in the beginning. The hi side charge of 150 just aint gettin it. If the charge was correct initially, it would be higher than 150 . The quickest and easiest check would be to add some more juice. However, I would also phone Vintage before hand to ask Noonies questions too. Let us know what you find.

 

mikejpss

Here is a link to the instructions I found. I assume it's what he is using. Have never worked on one of their systems, looks like most add ons less the ecu.
Your comments on the system.
http://www.vintageair.com/DownloadsS...el)%20Inet.pdf

Here are some more thoughts.
The system a closed, same as max cool (recirculate) in normal systems.
The very low eventual heat load due to good system efficiency is more prone to evap freezing if the comp is allowed to run.

And note their lack of an acuumulator.

They say to weight it in, which we both know is the most accurate method, but only if the design weight is accurate.
No way it should be 14 when weighed in.
I've almost always ended up with 34 to 39 using a quick superheat method with 134.

 

Agree with all of you comments. I dont like the idea of not using an accumulator as this encourages liquid back to the suction valves on the compressor which is a bad thing. Entrailed liquid is not so bad, but liquid "slugging" is trouble...The lack of an accumulator is troubling to me.
Just a quick read i did, but this system looks like it depends on heater functions (at least on the surface) as a way to blend in applied heat to maintain evap air temps, or, am i seeing this incorrectly?
You are correct that 100% recirculated air will tend to drop the evap temp/pressure. Maybe thats why the heater assist is used here?? Crummy design if thats the case, inho...
I know that all manufactures will supply a "charge rate" to thier system and have personally used this as a "minimum" scale. The ambient temps (and consequencial pressures) will always be higher in MY environment (south Louisiana) than those listed like at a Michigan factory for a GM car. In other words, if it says 1.8 pounds, thats a starting minimum for me here and it generally takes 10-20% MORE. They (northern factories) may be making the charge with the car doors closed ,lower temps and much lower humidity than I charge em with doors open, 90 degrees F ambient and usually 90+% humidity.
When all else fails, I use a SUPERHEAT method I developed over many years- I FEEL THE SUCTION HOSE at the firewall and at the compressor inlet- they should be ice cold without forming ice. And in Louisiana they're dripping like someone left a faucet running.