Be sure the thermostat is set in the cooling mode. Just setting the dial below room temperature will not activate the air conditioning if it is set in the heat mode.
The problem with plywood is getting in from here to there. It's heavy and getting a good grip is difficult...especially if you have to carry it for any length of time. An easy solution is to take a couple of C-clamps and tighten them on to each end. This will give you the handle you need to get a good, solid grip.
According to the U.S. Department of Energy, in 1997 the average house spent over $1300 in energy costs. 44% of those costs, or about $600, came from heating and cooling. Yet, by setting the thermostat down just one degree a home could, over an eight-hour period, reduce energy costs by 1%. Doesn't sound like much? Look at the math: If you set the thermostat back by 10 degrees for the eight nighttime sleeping hours, and did this for a whole month you could lower your monthly bill by 10 percent. Do the same for the eight hours you're at work and you're looking at 20 percent. For the average home this could mean a $20 savings on the monthly heating costs with similar savings for the cooling season. A programmable thermostat can ensure those savings and pay for itself in one season.