Accessing heater core
 

So, checking out the low airflow in the heater, discovered the blower fan housing in my 91 PA was covered with a dirty, oily residue. Unfortunately, digging deeper what I can see of the heater core, it too is pretty bunked up. So, I suppose is the AC evaporator. What I want to do is to access them from inside the car and use a combo of alcohol and compressed air to back flush the fins, forcing crap back into the fan housing where it can be cleaned out. Hoping to get feed back and advice in getting to heater core/ evaporator housing.