LMAO you guys. I don't know anymore than any of you do.
I do see an issue with that, and if you have noted your fan is indeed on with the AC, high speed not being on is quite likely IMHO.
I could get away with low speed and AC till about 95* temps. Then low speed wasnt enough and temps would creep up to 205*F or so.
Realistically, if the fan is pulling enough air, your car (with AC on, where high speed is running) should run at about 5* above your thermostat rating.
With AC off, then you have to wait till you get to about 208*F to get low speed to kick on naturally. if things continue to get toasty, high speed comes on in the high 220's (like Brian noted).
I'd take a look at the fan connector - high speed is known for getting toasty.
If one wants to ditch the stock set-up, I can't recommend the variable units from DcControl.com enough. You guys know how poor my butt is, and I still think it's worth every penny. I now run at 187* all day long except when it's 110*ish and I idle a lot - high speed simply cant keep up. That's a fan issue and nothing else.
Good luck.