Just installed new AC belt on may 2010 Denali. The installation tool/guide did not fit between the main pulley and engine; would not make it all the way around. I was able to install the belt without the tool though and it wasn't too bad and did not seem to damage the belt. Just put the belt in place, on the compressor pulley, off the main pulley and rotate the engine with a socket wrench.
Same freaking thing with the '10 Tahoe!! At least not the parts house rental units! The 'remover' tool that came in the rental kit worked great ,but not the installer tool. These are the plastic tools that are kind of an orangy-red color. The installer tool catches on what I think is the crank sensor. Luckily the sensor is in a metal housing that's bolted to the block, or I'd be enjoying that R&R, too!!
I had my bride hold a large flat-blade screwdriver against the block, and push on the belt near the A/C pulley, making sure the belt was tilted downward toward the block, and not the other way. I, then, turned the crank bolt until the belt popped into place. I did have to roll the belt back and forth a couple of times to get it to sit squarely on the pulleys, but got it done.
What a sh*tty idea! I guess since it's a 60K mile replacement, GM doesn't give a crap since it won't be covered on their 36K mile warranty. Did I mention what a sh*tty idea it was? Hell, my '12 Caprice 9C1 still has the idler!!
And I was joking with the parts house counter folks that 'remember when they told you to NOT use a screw driver to install a belt? Well, I guess they do now!' That was, indeed, how I got it replaced.