How can I access my central a/c's evaporator to clean it?

I know where it's located but it's inside a sealed sheet metal box. There are screws on one side of the plenum but the pipes running to the evaporator from the outside unit prevent me from pulling it open. The air coming out of the vents isn't as cold as it used to be and I've cleaned every other part of my a/c except for the evaporator. It's never been cleaned for the 28 years that it's been there. I can only imagine how much dirt and dust is on it.

How can I access my central a/c's evaporator to clean it?
If your unit is 28 years old you owe it to yourself to replace it. A high efficiency system will save you 35% on your electric cost. For example if your cooling bill is $300 per month then by replacing it you save $100 per month. However if you want to just clean the coil: If it is in a closet (upflow) you will have to remove the front cover of the cased coil. slide the coil out and then using hydrofloric acid, spray the coil from the under side, then rinse the acid off with water, it works best if the coil is removed %26amp; taken outside and cleaned. However I think you are wanting the least expensive way out. If the coil is located in the attic (horizontal) cut a hole in the transition and clean it with acid again rinsing it with water. Be careful with the acid, it will burn your skin and eyes if it gets on you. However it has been my experience that coils of this age range usually develop a freon leak after they have been disturbed. A licensed service company will usually do this for $250-350. Good luck. But it may not be cooling well for other reasons as well, for example, a dirty air filter, coils outside are dirty, or it is low on refrigerant. Best Of luck..
Reply:Take apart the air conditioner.
Reply:Are you sure it needs only cleaning? Have you checked the freon? That could be a huge factor.