Why'd my heater Stop working?

Hello, it does seem like you may have a system restriction due to what is likely a significant amount of accumulating corrosion over the last 33 years of the vehicle's life. It all depends, of course, and is subject to inspection. You'll want to have a professional power flush - in both directions - of your cooling system to see if there are restrictions and hopefully clear them. That is the best place to start. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops