Australian Car Repair Issues? Ask an Auto Mechanic for Answers ASAP
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The hvac housing is behind the dash and requires removing the whole dash, steering column and the dash cross bar support in order to remove the housing
If you have the air ducts exposed, at this point I would try using a shop vacuum to remove any debris. Use rags to block off all ducts but one and use shop vac to suck out any debris thru duct opening. Then stuff a rag in that one and remove a rag from another duct and repeat. Do this for all duct openings.