Small Rattle When at Idle with AC on - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 09-10-2015
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Icon5 Small Rattle When at Idle with AC on

I just heard a small rattle on my truck when it was in idle with the AC on. Turned Radio off to listen better, rev engine and noise goes away. Turn the ac off and the noise goes away. Seems to only be on when the AC is on or set to Max, not vent. Putting the truck in park removes the sound as well. I just replaced the alternator 2 weeks ago and the belt and the idler pulley due to a power issue. Could I have exposed something else? Any thoughts would be appreciated! 1999 ranger 4.0 V6 SuperCab 4wd

THANKS!
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Old 09-10-2015
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your AC pump clutch maybe failing , hence the rattle when idling with AC off
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Old 09-10-2015
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I may have stated incorrectly. The Rattle only shows up when the AC is on and the truck is in gear. I replaced the tensioner tonight as the autozone guy offered to just warranty it, and the idler pully. They suggested a slightly smaller belt as the tensioner looked to have no more room to give in it. I will admit that the tensioner does seem to be almost all the way out with the belt on. This belt is new. Could it be a bad bearing in the alternator? With the hood up, parking break on and listening, it sounds like the rattle is coming from that side of the vehicle. Can you tell me more about the AC Pump Clutch and how to diagnose that? Much appreciated!
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Old 09-11-2015
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the AC pump does not rotate internally all of the time , the AC pump utilizes a external clutch activated by a 12 volt source ( you will see the electrical connector )

the AC clutch engages the external pulley when 12 volts is fed to it ( when you turn on the AC )

over time the friction material used by the clutch does wear out ( the legs that hold the friction material keep bouncing off of the inside of the external pulley

basically it sounds like metal parts rattling around

as you stated - the rattle only happens when the AC is on -- that is a dead give-away
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Old 09-11-2015
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Thanks again for your reply. So do I replace the baring?Clutch? Whole unit? What should I look for? I see that replacing the clutch isn't super difficult from a few videos online. Should I just order the club assembly and bearing and replace or should I consider replacing the entire unis/housing? Thanks so much! I have replaced the alternator/ilder and tension, is this as easy as those?
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Old 09-11-2015
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if and when i will need to replace my AC pump

i will be replacing the complete pump assembly ( after the AC coolant is completely drained and removed fom the AC piping )

some special tools are required from what i have read about ,

does not make financial sense to do a rebuild yourself , since replacement parts are cheap now a days

plus the old AC coolant has been deemed toxic , and replaced wirh R-134
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