AC Too Cold! BRRRRR
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Well I'm in south Florida, so our radiant heat may be a touch higher than yours, but ajrothm in Houston should be very similar too.
I can't imagine their system up north, evap freezing all the time.
Agree with you on the charging method, I think that's the problem with the original poster biaggio, and why his mechanic doesn't interpret the readings properly.
Funny little story.
Some friends of mine do limos a few doors down from me and they always have a/c issues even with multiple fanned condensers and evaps etc.
They worked on one black limo for 2 days trying to get it to cool effectively. Best they could get was 65°.
At the time, I was doing a/c on a black BMW, had it sitting under a tree in the parking lot, all closed up, set on max, vent temp 33°.
They were amazed when they saw the thermometer and asked what kind of majic I did to get it so cold. (It was cutting out with a freeze switch, that's why BMW cost a little more, sometimes their design is a little better)
Little did they know that under normal driving in 95 temps and hot Florida sun, the vents were at 50 like they should be and that will pretty cold.
I can't imagine their system up north, evap freezing all the time.
Agree with you on the charging method, I think that's the problem with the original poster biaggio, and why his mechanic doesn't interpret the readings properly.
Funny little story.
Some friends of mine do limos a few doors down from me and they always have a/c issues even with multiple fanned condensers and evaps etc.
They worked on one black limo for 2 days trying to get it to cool effectively. Best they could get was 65°.
At the time, I was doing a/c on a black BMW, had it sitting under a tree in the parking lot, all closed up, set on max, vent temp 33°.
They were amazed when they saw the thermometer and asked what kind of majic I did to get it so cold. (It was cutting out with a freeze switch, that's why BMW cost a little more, sometimes their design is a little better)
Little did they know that under normal driving in 95 temps and hot Florida sun, the vents were at 50 like they should be and that will pretty cold.
Melting Slicks
Joined: Jun 2009
Posts: 2,343
Likes: 4
From: Anderson SC
My wife said tell you, to just make sure you use this car to do all the family grocery shopping - to keep those perishables fresh.
She added, that at Corvette events you are now nominated to be the guy that brings all the beer.
-W
She added, that at Corvette events you are now nominated to be the guy that brings all the beer.
-W
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
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.
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.
You hit the nail on the preverbial head...... Today I did a lot of water temp and AC temp testing.... When I first left my house with the AC on, vent temps went to 37-38* pretty quick, within 10 mins, I adjusted the Temp control wheel back just a hair and dialed it in to give me 41-42* vent temps....I did the exact same drive that I had done yesterday that gave me the freezing evap and I had no problems at all.....I continued to run the car through out the day with the AC on, eventually vent temps started warming up on their own to the 45-46* range so I rolled the Temp control wheel back to full COLD. Vent temps dropped to 41* for quite a while then eventually ended up at 42-43*.....Never had any freezing issue. So I am driving the car on and off all day, water temps are 200*+ and with our 92* ambient temp today and 50% humidity, at 3pm the Vintage air seemed to be struggling to hold a steady 44-45* vent temp with everything on max cold and thumbwheel on full COLD.... It would touch 43*, then cycle off...temp would go up to 45* and cycle back on....It would pretty much hold 45,*, no warmer then 46*, even with the blower on HI so....No freezing evap....I guess I will just have to pay attention to the outside air temp and the vent temp for the first 30 mins before I roll the temp to full cold on the AC....I think this is dumb as hell but.....
It is what it is I guess.....
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Oh also....Per Vintage Air's website...
II. Acceptable operating pressures.
A. R134 Type
1. High side pressures 160-250 psi, general rule of thumb is 2x times the ambient temp + 15-20%
2. Low side pressures, 6-12 psi in steady state, 14-15 psi average.
3. Vent temps in center vent, 36-46* F
Charge as follows:
R134- 1.8lbs
Looks like mine is in spec so I am gonna let it ride for now....But I still think its a tad low on freon...we'll see...
II. Acceptable operating pressures.
A. R134 Type
1. High side pressures 160-250 psi, general rule of thumb is 2x times the ambient temp + 15-20%
2. Low side pressures, 6-12 psi in steady state, 14-15 psi average.
3. Vent temps in center vent, 36-46* F
Charge as follows:
R134- 1.8lbs
Looks like mine is in spec so I am gonna let it ride for now....But I still think its a tad low on freon...we'll see...
Le Mans Master
Joined: Jun 2007
Posts: 7,666
Likes: 1
From: Where it's always hot as Hell-South Louisiana.
St. Jude Donor '07-'08-'09-'10-'11-'12-'13
Oh also....Per Vintage Air's website...
II. Acceptable operating pressures.
A. R134 Type
1. High side pressures 160-250 psi, general rule of thumb is 2x times the ambient temp + 15-20%
2. Low side pressures, 6-12 psi in steady state, 14-15 psi average.
3. Vent temps in center vent, 36-46* F
Charge as follows:
R134- 1.8lbs
Looks like mine is in spec so I am gonna let it ride for now....But I still think its a tad low on freon...we'll see...
II. Acceptable operating pressures.
A. R134 Type
1. High side pressures 160-250 psi, general rule of thumb is 2x times the ambient temp + 15-20%
2. Low side pressures, 6-12 psi in steady state, 14-15 psi average.
3. Vent temps in center vent, 36-46* F
Charge as follows:
R134- 1.8lbs
Looks like mine is in spec so I am gonna let it ride for now....But I still think its a tad low on freon...we'll see...
Cant think of any a/c system where you are required to massage the "cold" wheel at different times for a system to function properly/ Mine have all been "set & forget"...I'm just sayin...
i too think you have a short charge, probaly 15% short. IMHO.
1971, ac, air, california, cold, condencers, conditioning, corvette, decrease, evaporator, freezing, pressure, psi, suction, symptoms, vintage
