I have a 69 that came without ac. Wanting to add ac I was told the new style that is completely under the dash was the way to go. After running it last summer I am very dissapointed. No air volume. The fan is very noisy when on high and puts out almost nothing on low. After thinking about it the new unit is smaller and the air has to travel though flex tubes to get to the outlet vents. IS the original GM one better?  The fan is bigger, the coil is bigger and the air tubes are large smooth molded plastic. It would seem that it would blow a lot more air. Any suggestions on how to really cool a 69.

I, myself, do not know.  But I bet a dollar to a dounut that that Texan knows something about it!!

I am from the other end of the country, but I will tell you what I know.

Factory air cars had a number of differences.  They didn't have a left side vent, and the right side was vacuum operated.  They had more holes in the cowl area, and the hole in the firewall was much bigger.  There is a template in the AIM that shows how to cut the firewall to accept an A/C unit, and some of the other differences can be ignored.  We have a stack of under dash units, and some ducts.  Most of the ducts are reproduced. 

And they do a pretty good job of cooling the car.  They use basically the same cooling equipment, and the cab is a lot smaller than a '69 Impala.  The noise level is about the same as your heater.

Larry

Depending on the manufacturer of the aftermarket, add-on A/C unit, the one that I have had any experience with was crap. The unit itself isn't that bad, but the installation was done by blind 2nd graders, imho. Ask Dwain(longhorn294)...
The way they installed his, there was no way it would ever work. Even after me spending several days re-routing the ducts, and patching all of the huge gaps in the ducting they left, I don't think it was cooling properly, but it was a little better.
Then, after all of that, one of the A/C hoses under the hood breaks off!! It didn't just loosen, and fall off, it literally exploded. This spewed refrigerant all over the place, and...the jerks that did the install thought it would be sweet to put in some leak-finding DYE in the refrigerant....soooo...guess what the underside of Dwain's hood, and engine compartment looked like?
Dwain might have more to add, but all I can say is the system they used on his, which was one of the total, under the dash, nothing sticking out in the engine compartment systems, turned out to be totally junk...
Perhaps a different brand, or design will work better, as Larry says the ones he has work fine.

I installed Vintage Air TrueFit system last year in my 1969 non- AC car and it works great for cooling here with the Summer Heat, also installed an Aluminum radiator at the same time. Works great cooling and the engine stays cool as well even on the triple digit days here. You will need to install and idle compensator to boost your idle up while the A/C is running and you are stopped at a light but otherwise it is great.

I have installed two systems from Hot Rod Air.  Both are great and work well all the time.  Cost: around $1.000.  You can spend that amound every other year to keep your old system working.  Mine have both been in for more than 5 years and I have spent nothing after the initial cost.  My 2 cents.

Did you install it on your convertible? I am looking for a lot of air flow.  Top down with cold air in my face.  Its hot and humid in southern IN. I talked to hot rod air and their unit has a double squirrel cage blower. Does it have a lot of volume? Why did you use the hot rod unit instead of a competitor?

All are very good questions so let me start at the top.