When installing a car stereo can i connect the ground wire to part of the air conditioning unit to ground it?

Question

When installing a car stereo can i connect the ground wire to part of the air conditioning unit to ground it?

Answer 1

As long as it's a part that makes contact with the car's metal frame.

Use a continuity checker to see if that part of the air conditioner has a decent connection to the frame.

If you don't have a continuity checker, you can just use any low-voltage circuit  (a light bulb, wire and AA batteries would do fine).