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Improving efficiency of factory ac system in '67 GTO
Prior to removal of the engine and the A6 compressor I run the system and it cooled 'okay' on a 75 degree day with the fan on high but I don't see it working well once we gets up to 90s here in NC later this summer. Are there any ways to make the factory system more effecient? Not sure if it was running r134a or good old R12 when I removed it and I don't know if the POA valve was changed if it was running r134a I did read a thread here recommending changing the fan out to a more modern unit to increase air flow. What should I consider when reinstalling the system to get max cool air?
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What about the setup itself, even if mint condition factory set-up for R-12, a simple regas with R134a and no adjustments will not find the results or improvements wanted. Along with new hoses, o-rings, drier etc as per regular AC service, also seek an adjustable pressure switch to dial in the preferred settings, and even look at the higher performance parallel flow condenser. I'll keep it vague as early models with POA aren't my thing. Perhaps have a browse through thepartguy.com for ideas.
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If it was running R-12 with all the original equipment, it would've probably been cooling very well. Those old R-12 systems would freeze you out of the car and the components were best suited for that higher molecular weight refrigerant. A common complaint when converting to R134a is reduced cooling, and the main reason for that is outdated components better suited for R-12, in particular the condenser. The old style tube and fin condensers don't have enough surface area to appropriately dissipate the higher heat conductivity of R134a, so upgrading to a parallel flow condenser and changing out your old clogged evap core will pay dividends in the performance of your AC system. New lines and a more efficient compressor wouldn't hurt, either. If you want to stick strictly to an A6 compressor, the best new units are sold by a company called Alma products, as they used the same tooling GM used. Another option are the newer style aluminum-bodied A6-derived compressors you'll see - they have the same dimensions as an A6, but are lighter, more efficient, and made of bare aluminum rather than painted steel. Finally, upgrade to a Sanden compressor for peak efficiency; but they're smaller in size than an A6 compressor, so you'll probably have to find brackets that'll mount it to your engine.
Blower motors are a point of contention for the stock HVAC systems, sadly. Our old cars didn't have as efficient ducting as modern cars do. Measures you can take to maximize the CFM output for each given blower setting is to make sure all your ductwork is accounted for (oftentimes parts are missing); reseal the main distribution duct to the heater/AC box with new foam; add foam to the slide-in joints for all the ducts to further seal in the system (which the factory did not do) or wrap the joints with ducting tape; make sure your AC and heater cases are properly sealed to the firewall; make sure your blower motor is properly sealed to the firewall; make sure your diverter doors and actuators hold vacuum and work and that the vacuum lines for the different modes are all in working order; and again, replace your evap core. While it may never blow with as much force as a modern car's blower motor, you will maximize how much CFM it can output by taking these measures. There's a thread here somewhere about swapping the blower motors for a modern unit that can be retrofitted and alleged to output more CFM, but the results were ultimately unfounded. I think the blower motor in question is for Astro vans from the 80's and 90's, and although they do fit, they apparently didn't make much of a difference. I don't think it's a matter of the blower, I think it's a matter of the distribution of air through the ducting. |
I'm doing a 68 Firebird right now. I installed a parallel flow condenser and a POA valve eliminator kit that turns it into a cycling compressor system. haven't got it charged yet but I can let you know how it works.
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I just finished rebuilding the A/C on my '86 K5 Blazer. Switched to R134. I replaced all components. The condenser, and evaporator, are parallel design with noticeably more core surface area. I also switched to appropriate low pressure switch. I installed a variable orifice valve as well. Variable is supposed to improve low speed performance. Just fired it up yesterday. It was only about 70F outside. But the air was incredibly cold coming from the ducts. I wish I woulda stabbed a thermometer in there. We'll see how it does when it gets really hot out.
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As you can see, common for evaporators to be clogged also. You might check that first. My mom had a Grand Am with weak A/C. The factory has sprayed sealer over half of the evaporator core!!!
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In my 67 GTO convertible, I just finished installing an OEM POA valve that was rebuilt and recalibrated for 134, a new high flow aluminum condenser, new drier/accumulator, and new lines. 20 years ago I had just charged with 134, but it never cooled well. These changes made a drastic improvement…the center vent gets really cold to the touch….. haven’t put a thermometer on it yet….now I just need to work on improving the air movement… kinda get spoiled by the air flow in newer cars…
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sounds like originally it may have been low on refrigerant. if you were closer i have a stash of r-12. ever come to detroit?
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