Need help with friends car

OK, so the car is a 2000 Daewoo Nubira with a 2.0 dohc, unsure of the miles.

The car runs fine(for a daewoo) and the temp gauge reads normal untill the A/C is turned on which causes the temp to climb untill the A/c is shut off.

Both the normal fan and the A/C fan turn on and run. The thermostat was just changed and both top and bottom hoses get hot so the T-stat seems to be working. The oil doesn't show any sign of coolant and the coolant that was drained during the T-stat changed looked fine.

What is the next thing to check? A radiator/coolant flush is $50 or so and a new radiator is $100. They don't have a lot of cash to throw at the car, so I don't want to just jump to it.

That's a pretty good description of the way my wife's Cherokee behaved with a mostly blocked radiator. The extra heat from the A/C overwhelms what little cooling capacity is left.

I'd be tempted to try to and flush the radiator and see if that improves matters, especially if you can pull it yourself and try to back flush it with a garden hose.

Worth a shot, are there any cleaners I could try? Or should I just use water?

Take the rad out, lay it down, fill it with muriatic acid, rinse it out well, throw it in the recycling bin and buy a new rad.