Is this a bad idea? I know it seems unwholesome and a bit wasteful, but what I want to know is if it’s bad for car in some way, like does it make it more likely you’ll overheat the engine?
Few cars use a thermostat to regulate air temperature inside the car, so the air conditioner will not work any harder trying to cool all outdoors than it will trying to cool the car when the roof is up. The A/C is cooling air it takes from outside of the car, unless you have the recirculation switch on.
I drove my convertible with the A/C on and the top down quite often. Never overheated the engine.
I knew a girl once who would hop in her little convertible, put the top down, crank the A/C up, hike her skirt to get some sun and drive very fast. She was wonderfully unwholesome.
Whether or not it’s wasteful is completely subjective. Both having the top down and having the A/C on put additional load on the engine. You’re more likely to overheat the engine with both these conditions than without them, but whether you would overheat depends on the specific car. As noted above, I’ve seen cars that would cruise at high speed for long periods with the top down and the A/C on max. I’ve seen other cars where you had to run the heater at full blast on hot days to keep from overheating. If you’re going to drive a $50K convertible at 90 miles an hour, saying it’s wasteful to put the top down and run the A/C is being penny-wise and pound-foolish.
On preview, I see that the previous reply is particularly apropos given the poster’s nym.
When my girlfriend is bombing around town in my Mighty Mini Pad (example only, not mine), the AC runs full blast constantly. So far there have been no problems whatsoever, except of course that the Mini Pad loses a significant amount of power to the AC compressor.
We recently drove straight from the Georgia border to Washington, DC, top down, AC full on, 85 mph most of the way on a hot day. The only noticeable effect was a decrease in fuel mileage from 33 mpg to 31.5 mpg compared to the trip down, which was at night with the top up and the AC off. Total cost to me was a little less than the price of a gallon of gas.
(Hey, I used to drive naked on long trips, but with the top down it’s just a little bit impracticable on the highway. So now I calculate and memorize my fuel consumption in my head instead.)
Your results will of course vary, probably widely if your car isn’t the size of a sardine can. If your car’s cooling system is running properly I suspect it won’t be a problem. As far as your potential anxiety over such a practice being wasteful and unwholesome, well, you’re going to be the one paying for it, right?
It is ‘more likely’ that you’ll overheat the engine but it is still very very unlikely you’ll overheat the engine on a modern car in proper condition. Kind of like “Yes, being 4’6” is ‘taller’ than 4’5", but it hardly makes you ‘tall’.