Air conditioner making noise - suggestions requested

[CRUZTAKER]

Not the Marauder, but similar platform.

I sealed the deal recently to sell my immaculate '99 Grand Marquis LS with 22,000 original miles.

I drove it a couple days, and washed it up nicely. I also washed the engine compartment.

One day later, I now have an awfull rattling sound coming from air conditioner unit under the hood. The rattle does not change with rpm.

I sprayed belt dressing on the serpentine belt and it quited up, but soon returned. I then sprayed a bit of WD40 on the pully, on the front of the air conditioner unit. This audibly increased the volume of the rattle.

Watching the unit (A/C OFF) as its pully turns while the car is running at idle, I see the clutch occationally engage, and the outer unit spin in conjuntion with the inner unit pully. It stops within moments, and starts again, continuing this on - off process.
This happens with the A/C on as well.
It sounds as if the A/C does indeed engage and blow cold air if turned on within the car.

The rattle is awfull now at day two.

I need to correct this in some way before delivering the car.

Any suggestions?

[fastblackmerc]

Sounds like the A/C clutch may be on it's way out or the compressor is on it's way out.

[Motorhead350]

Take the blower motor off and spray it with WD-40. Spray the wheel that spins. Does this only occur when the A/C is working or whenever you have the car on regardless of the fan?

[RF Overlord]

Bear, the AC compressor should not be operating at all with the HVAC off. Are you sure it wasn't in defrost? That also runs the A/C to dehumidify the air.

If it's short-cycling, that usually means the system is low on refrigerant.

As far as the rattling noise, it sound like the compressor clutch. Try unplugging it so it doesn't engage and see if the noise stops.

Not sure if you can buy just the clutch disc, but the whole thing with coil and pulley will be around $100 to $125.

[CRUZTAKER]

Well thank you, but after a quick visit to the local RAD-AIR it turned out to be a failing serpentine belt.

A little belt dressing and wala, noise gone.

I won't deny, there is likely something going on with the A/C as the replies here indicate.