Sorry for the mis-spelling...it's after midnight and im a little on the tired side.

 

That means your alternator belt is too loose.

Most people don't understand how an alternator works. An alternator requires power to make power. Not only does it require mechanical power (from the engine) but it also requires electrical power. An alternator uses electro-magnets and inductance to generate power. In order to produce more power, the alternator will require more power to the magnets, which puts more magnetic resistance to the alternators spinning. Since the more power it outputs the harder it is to spin, sometimes you only hear the loose belt when there is load on the electrical system.

Simple version: The alternator becomes harder to turn when it has to generate more current. Tighten your belts.

 

The Z31 belts need to be tight. I've had the same problem with the power steering belt. When you put new ones on, they'll loosen up a bit once they wear in. You'll have to tighten them a couple of times to make sure they don't squeal.

I'd also make sure nothing is leaking on them (oil or water) which could also cause them to squeal.