R4 A/C Compressor Help! Spin by hand? - General Engine (Non-Gen Specific) - Firebird Nation

Jump to content

FirebirdNation.com is the premier Pontiac Firebird forum on the internet. Supporting Members do not see the above ads.
- - - - -

R4 A/C Compressor Help! Spin by hand?

  • Please log in to reply
1 reply to this topic

#1 GBousley


    Firebird Newbie

  • Full Member
  • Pip
  • 11 posts
  • Gender:Male
  • First Name:Gregory
  • City:NA
  • State or Province:TX
  • Country:USA
  • Year: 1992
  • Make: Pontiac
  • Model: Firebird
  • Engine: 5.0
  • Transmission: 700r

Posted 16 June 2020 - 05:00 PM

Hey, all!  I've got a 92 firebird 3rd gen which has the GM r4 a/c compressor. I am beginning to suspect that my compressor might be starting to fail. When running it, the engine felt like it had drag on it with a little rough idle. I know the pulley and bearings are good since I replaced the pulley assembly (with bearingings) very recently. But the compressor still feels stiff. I thought compressors should be easy to spin by hand when the engine is off, but this one is stiff and takes quite a bit of force to get it to spin by hand. When it does I do not hear / feel any grinding from the compressor. Should I be able to easily spin by hand? Currently it takes 2 hands gripping tightly and about as much force as I can exert to spin it just a little bit at a time.


Thanks in advance!!!

#2 ZumpTA


    Firebird Master Tech.

  • Administrator
  • 2202 posts
  • Gender:Male
  • First Name:Tony
  • City:Holiday
  • State or Province:FL
  • Country:USA
  • Year: 1993
  • Make: Pontiac
  • Model: Trans Am
  • Engine: LT1
  • Transmission: 6-Spd

Posted 16 June 2020 - 07:20 PM

If the clutch is not engaged, and the drive belt is removed, the pulley should spin freely and without any effort.  If you have powered the clutch and are attempting to turn the compressor over, yes it is quite hard, just like trying to turn over an engine by hand without removing the spark plug. It takes 20+ HP to drive an A/C compressor. Compressors have pistons in them like every other "air" pump and the more they "compress" the more resistance to compression they build up.  If the compressor is out of the car, "clutch engaged" it should be nearly as easy to turn over as the free-spinning pulley because there is no pressure buildup, and therefore, no "compression" taking place.  ...now, how much force should a perfectly functional compressor in a charged/closed system require to turn over?  Good question.  

"There are two major products that come out of Berkeley: LSD and UNIX.
We don't believe this to be a coincidence."
-- Jeremy S. Anderson

"Man is the best computer we can put aboard a spacecraft...
and the only one that can be mass produced with unskilled labor."
-- Wernher von Braun

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users