A/C compressor slowing down my car.
Thread Starter
Pro
Joined: Mar 2005
Posts: 569
Likes: 0
From: College Station Texas
A/C compressor slowing down my car.
I have recently noticed that if I am driving with my foot off the gas and turn on the A/C I can feel the car slow down. It really bumps it right when the A/C is turned on. It is most dramatic when I am going about 5 mph in 1st without my foot on the gas. The best way to describe it is just a bump. I can't tell if the car is noticeably slower with it on after the bump, but you can definately feel it right off for an instant. Do your cars do this as well?
Race Director
Joined: Aug 2003
Posts: 13,421
Likes: 8
From: Lake Mary Florida
Well gross engine output at idle is about 5 hp. The power required to turn the engine at idle in park or neutral is about 5 hp. The air conditioning compressor uses about 2 hp which is about 40% of the engine's idle output.
Last edited by 93JetJocky; Sep 29, 2005 at 12:43 PM.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
What does it feel like on the highway at about 65 mph and on flat smooth road? You may feel a very slight dip when the compressor cuts in. Does the compressor sound noisy when you have the hood up and watch it cycle? Does it cycle on/off very quickly?
Intermediate
Joined: Jul 2005
Posts: 47
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From: Aloha Oregon
Yea, I don't think you have anything to worry about. Any compressor takes a significant amount of power when it first engages. You will notice it more at low speeds. If the compressor stalls you will DEFINITELY notice it at any speed.
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But at wide open throttle you won't get any drag, the compressor disengages itself so I'm told.
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Yes, AC compressor deactivates at WOT, just like everything else. Its normal for you to feel the drag on the engine.
Racer
Joined: Apr 2005
Posts: 435
Likes: 1
From: Worth IL
Originally Posted by Saisling
It's normal for the AC to drain a bit of power
when idling my 84 throws 13.9 amps yet when I engage the
AC it goes to 11.8 to 11.6,also while driving and appliying the
brakes and slowing down it feels like I'm dragging an anchor!!!
could it be that it needs a new compressor???
sorry if I highjacked this thread
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Originally Posted by Poncho C4
How normal should it be!!!
when idling my 84 throws 13.9 amps yet when I engage the
AC it goes to 11.8 to 11.6,also while driving and appliying the
brakes and slowing down it feels like I'm dragging an anchor!!!
could it be that it needs a new compressor???
sorry if I highjacked this thread
when idling my 84 throws 13.9 amps yet when I engage the
AC it goes to 11.8 to 11.6,also while driving and appliying the
brakes and slowing down it feels like I'm dragging an anchor!!!
could it be that it needs a new compressor???
sorry if I highjacked this thread
Team Owner
Joined: Oct 2000
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From: Fort Knox, KY
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Well you've got what? Fifteen pounds of refrigerant under pressure that the crankshaft's got to overcome. You're bound to feel a slight bump in load.
Heel & Toe
Joined: Sep 2005
Posts: 17
Likes: 0
Originally Posted by VB Black Ice
Well that explains why my air always blows hot 
"while driving and appliying the
brakes and slowing down it feels like I'm dragging an anchor!!!"
- it's supposed to do that.
No seriously, how can you tell a difference if the A/C is affecting power when on the brakes?
While cruising you should be able to feel it kick in and drain a little power, probably lose a little grunt unless you are WOT,
The RPMs shouldn't drop enough for voltage to drop, unless your A/C blower fan is draining it that much. A/C should kick on your other cooling fans also, which would cause a little drop too - more if you have some higher amp fans isntalled.
