A/C question

[sgaylord]

I just completed installing Vintage Air in my 69 Burb. I think I have it right but would like someone with more ac knowledge than me to confirm.

Pulled 30hg vacuum for 30 mins (twice) and let set to verify no leaks.

After verifying no leaks, I started the charge. (Engine at idle 700rpm's ac on, fan speed - high). Using my gauges and scales (30lb r134a canister) I put a little more than 2lbs into the system. I know VA states 1.8 but I read on here that you should go until you get the pressures you need according to your ambient temp. Today it's 96deg so using the chart below I was supposed to go to 50-55 low side, and 275-300 high.

Ambient Temp (ºF) Low Side High Side
65 25-35 psi 135-155 psi
70 35-40 psi 145-160 psi
75 35-45 psi 150-170 psi
80 40-45 psi 175-210 psi
85 45-55 psi 225-210 psi
90 45-55 psi 250-270 psi
95 50-55 psi 275-300 psi
100 50-55 psi 315-325 psi
105 50-55 psi 330-335 psi

My pressures are 35 low and 280 high. I got chicken and did not want to push the high side any higher because I also read on here that you should never go above 300.

My vent temps are:

Center vent at cruise speed (60 mph) is 38 deg.
Center vent at idle 42 deg.

Static pressures are about 130psi both sides after stopping engine and letting system sit for about 30 mins.

Is this ok?

Thanks,
Steve

[68gmsee]

That's refrigerator temps!

But, since everything is brand new, it sounds about right.

On the a/c's that I have recharged, I usually try to get in the mid 40's or slightly higher and it usually is fine for me.

[dznucks]

How well did the install go? i am trying to decide between a vintage air, old air, or CAA system.

I am leaning towards the Old Air.

I dont know much about working on A/C so i cant answer your questions. I am about to learn. But if you got that cold of air coming out of your vents, i would say your good.

I am curious as to what every one else has to say.


Roll Tide brother.

[Richard H.]

The high side should be 2.5 times the ambient temp , windows open at 1500 rpm. Try that and see where your low side reads. 700 rpm is to slow.

[cparman]

I have only done ONE Vintage air system, but have done several CAA systems. When using r134a, I have had the best luck by undercharging them just a bit. My experience is mostly with CAA, but your pressures seem high for an aftermarket system. Typically, I will see 15 lbs on the low side and 150 on the high side. Your temps at the vent are awesome! Like someone said, for factory systems high side should be 100 + ambient air temp + 20% or so. SO, today it was 85 + 100 + 36 = 221. IMO your pressures are a bit high.

[sgaylord]

Thanks everyone for the replies. Do I need to do anything to the system or is it good to go? Will having the high pressure in the 280 range be a problem if I leave it? Since she is blowing this cold I really dont want to do anything if I done have to.

Tomorrow I am going to do another test. This time with a different thermometer just to verify the readings.

dznucks
Re: A/C question
How well did the install go? i am trying to decide between a vintage air, old air, or CAA system.

I am leaning towards the Old Air.

I dont know much about working on A/C so i cant answer your questions. I am about to learn. But if you got that cold of air coming out of your vents, i would say your good.

I am curious as to what every one else has to say.


Roll Tide brother.

The install went fine. I have done a couple VA installs. One on my 69 Camaro and then this one. I have another kit for Jezebel when I get to that stage. Might say I like VA.

Richard H.
Re: A/C question
The high side should be 2.5 times the ambient temp , windows open at 1500 rpm. Try that and see where your low side reads. 700 rpm is to slow.

Richard,
I will give this a try tomorrow and see how it goes.

cparman
Re: A/C question
I have only done ONE Vintage air system, but have done several CAA systems. When using r134a, I have had the best luck by undercharging them just a bit. My experience is mostly with CAA, but your pressures seem high for an aftermarket system. Typically, I will see 15 lbs on the low side and 150 on the high side. Your temps at the vent are awesome! Like someone said, for factory systems high side should be 100 + ambient air temp + 20% or so. SO, today it was 85 + 100 + 36 = 221. IMO your pressures are a bit high.

Thanks cparman

How should I address the high pressure? Should I bleed the system down a bit to equal the formula you have above? What about the low side?

Thanks,
Steve

[sgaylord]

Latest update:

Today when I went out, I hooked up the gauges without starting the truck and both the high and low sides registered 80psi. I guess I did not allow the system to set long enough when I stated yesterday that the static pressure was 130 on both sides....

Today I ran the truck at 1500 rpm's and noticed that the longer I ran the truck with AC on max, the higher the pressure would go on the high side and the lower the pressure would go on the low side. Is this normal? I did not let it run but about 10 minutes and the readings ended up 28 on the low side and 225 on the high. My temp gauge at the house said we are at 85 deg today. I checked the vent temps with a different gauge and it registered 42 deg sitting in the driveway.

Questions:

What about the pressures? Why were they going down? Do they steady out at some point? Did I let it run long enough?

Since my vent temps are good, does this mean I am ok and I don't need to do anything?

Thanks for putting up with my constant questions. I don't have much experience with ac. After this I will know a bit more for the next project... :-)

Steve

[scott's69]

Your gauge readings sounded about right. Ive installed Old Air and several Classic Auto Air units in both trucks and cars. CAA has given me the least troubles.

[umwtnt]

If you did not have an external source of cool air blowing across the condenser the high side readings will increase. Remember the condenser is there to help remove the heat from the refrigerate. That requires air to blow across the condenser. Your fan blades do not always perform that task well while sitting still. I normally will have a fan blowing across the condenser to get normal readings, as if your driving down the road. Your pressures sound good, run the system for a while and see how things evolve.

[cparman]

scotts69 and UMWTNT have good points. Get the truck running tomorrow, with a fan in front of the truck, engine running, 1500 RPM, and the A/C on. IF your gauge readings are close, stop messing with it. I am thinking you are very close to being very good. If you chose to let the pressures down, bleed a bit off of it and see what happens. YOU'RE DAMN CLOSE

[BOZO]

Check out the Automotive Air Conditioning Information Forum provided by
www.ACkits.com. There's not much that can't be answered by these guys. They have solved all my questions and more.