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Slight surge at idle

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Old Feb 25, 2014 | 12:05 PM
  #1  
bsmd2005's Avatar
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From: Queens, NY
Year: 2000
Model: Cherokee
Engine: 4.0 Litre
Default Slight surge at idle

Hi guys,
Quick question, noticed that when the HVAC is on, any setting, I get a slight cyclical surge in idle. I hear a clutch kicking in and off at the A/C, around 15 second intervals. Low pressure in the A/C maybe?
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Old Feb 26, 2014 | 02:44 AM
  #2  
Roler's Avatar
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From: Australia
Year: 1997 (RHD)
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Your e-fan tends to cycle on and off when you have A/C on (and defroster I think, but I've never have used that setting here, in the 5 years I own mine haha).
This is normal operation.
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Old Feb 26, 2014 | 03:06 AM
  #3  
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Year: 1991
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Engine: 4.0 HO
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Roler is correct, however if you have a low refrigerant charge the compressor/fan will cycle more often. If it's happening every 15 seconds I would think that your original thought of low pressure is correct.
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Old Feb 26, 2014 | 11:38 AM
  #4  
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From: Northern Illinois
Year: 1997
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Originally Posted by bsmd2005
Hi guys,
Quick question, noticed that when the HVAC is on, any setting, I get a slight cyclical surge in idle. I hear a clutch kicking in and off at the A/C, around 15 second intervals. Low pressure in the A/C maybe?
My '97 FSM says that cycling of the AC compressor is normal if it cycles less than 10 times per minute (every six seconds).
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Old Feb 26, 2014 | 12:40 PM
  #5  
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Thanks, much appreciated! I will check on the A/C pressure, just to make sure.
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Old Feb 26, 2014 | 12:55 PM
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You should know that the refrigerant pressure is affected by ambient temperature.
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