1999 Pontiac Sunfire Steering Wheel heavy, almost impossibl

If it is stiff in both directions, more than likely you lost pump pressure. I believe this pump is driven off the camshaft at the trans end of the engine, I would check the condition of the belt. It is odd that it failed all of a sudden, and is exhibiting no noise.

If it is indeed the power steering reservoir that you checked, and the fluid is full, even if it had a leak you would still have noise during operation, until the fluid got so low. If it(pump) is not being driven, and it is full, you can expell fluid out the cap eventually just via expansion. Like I said, check that the belt is still attached, and the pulley is turning. There are some cases where the pump shaft can break, and everything looks normal, but the pump is non-functional. About the only way you can confirm it would be with a power steering pressure analyzer, it's not readily available in most cases. You could disconnect a pressure line, but if there is any pumping action whatsoever, it will make a mess in a hurry, and could cause injury.

Since that belt is away from the other drive belts, it can get overlooked. Often times the belt is what fails, gives up just due to wear. Thanks for posting the results.