http://wiki.seloc.org/a/Heater
and found this......
DIY air filter
Modification to prevent grit from being sprayed onto the dash. You will need:
1 used stocking. 10 denier is best for optimum fan performance. Higher deniers can reduce air flow too much. Lace top optional.
Difficulty: Very, Very easy.
Directions:
Open the front service compartment
Remove one end of the air hose
Stretch stocking over air hose
Refit air hose.
Remember to replace or adjust the stocking annually, or when you notice a drop in airflow.
