I used the air conditioning for the first time yesterday and I noticed a drastic reduction horse power while I had it on. I also
noticed the engine noise changed considerably while accelerating. Kind of a tinning resonating sound. Is that normal?

 

never happend to me. maybe a little less HP....but not drastic. and the only time i hear the ac is when i just turn it on and it needs to get cranking! other than that...no problems with it.

 

I don't notice a difference in the sound but on my car the clutch definitely graps more abruptly with the A/C on. I have to explain it to my passengers so they don't think I don't know how to drive a stick. I think my 300ZX did the same thing.

 

I don' t feel the HP reduction, but there is definetly louder nosie coming from the engine bay. I ask the Nissan's service manager, he told me that's normal because the compressor has to handle high pressure....I don't quite understand, but I know that Nissan's quality is not what I would expected. I just had a rear bumper replace by nissan, and it still doesn't fit correctly!!