Creaking noise when air conditioner is on

I have a '93 SL2 with 145,000 miles. When I use my air conditioner there
is a creaking noise (like a door slowly opening in the horror movies)
under the left rear of my car. This is easy to reproduce if I press down
on the trunk. However, this only happens when I use the air conditioning,
which is very rare, so I'm hoping that nothing is about to fall off.
Could this be a heat issue? Any hints?

Meph

 

The air conditioner makes a different type of vibration than just the engine
alone. Probably something loose or worn in the rear end of the car. Just for
peace of mind, you might want to get the suspension checked. If you can push
on that corner and hear a groan, something is wrong.

I didn't like the sound of my brother-in-law's car one day. He ignored it
till on the highway, the rear end went bang (the axle bearing had seized and
sheared the axle), then dropped and the rear wheel passed him. The car
skidded along on the gas tank and was pretty well engulfed by the time it
came to a stop. Luckily the BIL got out with only singed hair. 'nuff said.

Oppie