Talk about a timely question! I'm in the process of wrapping up an installation on my 69. I went with a system from Classic Auto Air
, one of their "Perfect Fit" systems. My car was originally a factory air car, but I opted to replace the system anyway for a few reasons: 1) my cam is "borderline" at making enough vacuum to operate all the doors and valves on the factory system, 2) I wanted to convert from R12 to R134a, 3) Even though I could have converted the original system to run on R134a (sort of), I was still concerned about the vacuum issue and didn't want to take the chance of re-fitting it and replacing other parts that needed it (like the compressor) and still having a non-functioning system.
I found the guys at Classic very willing to work with me on assembling a kit for my car. That said though, it's still not a "plug and play" deal because, like Vintage, they don't have a turn-key kit for the GTO. They do have a kit for the Chevelle though, so that was my starting point.
There were a few areas in installing the kit that I had to do some of my own re-engineering. One was in the condenser (part that goes in front of the radiator). The GTO core support is quite a bit different from the Chevelle. The guys at Classic provided me a different (larger) condenser and a "universal" mounting kiit and also a "universal" A/C hose kit that consisted of lengths of raw hoses and an assortment of fittings of various types, sizes, and angles. I had to do some trial and error planning in order to mount the condenser so that there was a smooth path to route and connect all the hoses, but that part wasn't too bad. I wound up mounting the receiver/dryer directly to the engine-side of the core support, close to the condenser.
The mounting brackets for the compressor took more work. My car, being a factory A/C car, already had the third crank pulley for the compressor so I wanted to use that, instead of the "kit instructions" solution of driving the compressor off the same belt as the alternator and just using a longer belt. That meant I had to move the compressor rearward about an inch or so, modify the brackets some, make some spacers, and change some of the braces. I didn't like their idea of using the alternator belt to drive the compressor also because that would have left me with just the power steering pump belt turning the water pump, and that section of belt that would have been between the alternator and the compressor sure looked long to me. Also, the mental image I got of what it would look like with the alternator belt running to the compresor and passing ABOVE an empty groove in the water pump pulley was just distasteful to me. It took some effort to use the original pulley, but I got it done and I like the result.
By far the hardest part of the whole install was adapting the factory Pontiac A/C controls to work with the unit designed for the Chevelle. First was the problem of "direction". The Pontiac control sliders/cables for both the mode (heat, cool, defrost, etc.) and the temp (cold/warm) "push" when the unit needs them to "pull" and vice versa. The mode control on the factory unit isn't a cable at all, it controls a vacuum valve that opens and closes various doors on the factory system to route the air where it needs to go.
I wound up solving the mode control by drilling a small hole in the slider and attaching one end of the control cable, then having the cable attach to the dash unit from the "right" instead of from the "left" side as it was designed, This turned out to be a better route for the cable anyway in terns of length and smooth operation. For the temp control, I replaced the heater water valve supplied with the kit with one from NAPA that operates in the correct orientation (push = on) for the Pontiac.
Another thing I had to do was to modify (cut) the original plastic defroster duct/plenum to clear the top of the new behind-the-dash unit and also to add provisions to it for connecting the flex hoses for the new kit (with the factory system the defroster plenum connects directly to the factory heater-a/c box behind the dash). I had to think for a bit about cutting that plenum up, but I solved the problem by finding and purchasing another one, so I'll have a complete plenum on hand if I ever decide I want to re-install the factory heat-a/c system.
Another place where I deviated from their instructions was in the wiring harness and on the blower motor speed switch. On the Chevelle, the blower motor is only three speeds and also contains the "on/off" function for the system. On the Pontiac, the blower motor is 4 speeds and "on/off" is controlled separately by the unit mode slider (heat, a/c, defrost, etc), So, rather than use the blower switch provided with the kit, I instead modified their wiring harness so that I could continue to use my 4-speed blower switch and control on/off from the mode slider. Adding a 4th blower speed to the 3speed blower the unit comes with, required a little creativity on my part
- but I did it and actually made it work. With a little imaginative electronics tinkering, I added a "low-low" speed that is just a little slower, so now I've got low-low, low, medium, and high all controlled by the factory switch.
Another side effect of working with the universal condenser and hose kit, is that I had to lay out and measure my own hoses, then select the right fittings to go on them, and THEN find a place that could crimp the a/c fittings onto the hoses for me after I'd layed everthing out and cut them to the right lengths. Luckily for me, Classic Auto air is also in the Dallas area where I live, so once I got everything planned out, they did that for me for free. It did however mean that I had to make a special trip over there to get that done.
I've got photos of all this work I've done, I just don't have them organized yet. In fact, Classic told me they were very interested in me showing them how I installed everything (I bet!) so if they'll make me some sort of "deal", perhaps I'll share with them.
NOW: There are some things about these aftermarket a/c systems that I didn't realize. I think this is probably going to be true no matter whose you use, so keep this in mind before you opt to go this route.
Drawbacks of using any aftermarket kit:
1) All the air flow is "inside" - there's no such thing as one mode where the unit is drawing air from the outside and anothere where it's drawing air from inside the vehicle and recirculating it. It's always in "recirculate" mode, even in heater mode. The vents to outside air behind the kick-panels near the floorboard have to be blocked off.
2) The aftermarket unit doesn't have as many "modes" of operation. The factory unit had 5 different modes for heat, a/c, defrost, and various combinations thereof. The aftermarket units generally only have 4: a/c, heat, defrost, and a 4th that miixes heat and defrost.
3) Because of those two items above, there are going to be some settings on my dash controls that are "dead" --- they won't do anything, or at least they'll be the same as the settings next to them. I don't like that a whole lot, but there's nothing I can do about it.
4) The behind the dash aftermarket unit is "bigger" in some dimensions than the factory unit, most notably depth, so I may wind up losing some glove box depth in the deal.
5) The A/C hose outlet from the new unit only has connections for 4 flex hoses, not 5. That means I'm either going to have to forgo using the lower lap-level a/c vents and just use the three (left, center, and right) in the dash. I haven't decided what I'm going to do on this one yet. I might see if there's a way to modify the factory lap vent plenum to work on just one feed hose, or I might just forgo installing those vents at all.
So, as with everything else "after-market", the phrase "bolt on" continues to be a big joke. To be fair though, this kit was never promoted as being a direct fit for the GTO so I know going in that it was going to take some effort to make it work. The one thing that was a surprise, that -might- have made me reconsider had I known it in advance, was losing the outside air vent function. Probably though I still would have wound up making the same decision.