Question about 2002 Ford Expedition

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Idles low when ac/heat is on and lights dim

Idles low(600) when ac/heat is on and headlights dim. recently replaced alternator(was doing this before replacement). voltage is at 15 with lights on but drops to 13-12 when blower at full blast. when i lower the blower speed the voltage rises. also when i speed up rpms. when it is idling low say at a stop light you can hear the blower speed slow down then pick up when you drive off.( rpm increase)

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Fix the idle speed to 850-900 rpm
check the alternator and voltage regulator as the voltage should read 14.5-14.8 volts dc at 1000rpm or higher regardless of what is running
have it bench tested by an accredited auto electrician

Posted on Aug 04, 2017

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Posted on Jan 02, 2017

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SOURCE: 2004 Ford Ranger Low Idle

I figured out what was going on. supposedly on ford rangers the Idle Air Control Valve (IAC Valve) goes bad. i got a trouble code looked it up and sure enough it is the IAC Valve. Under 100 bucks for the part

Posted on Jul 13, 2008

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SOURCE: gmc sonoma voltage fluxuation & headlights dim at night

I would still have the alternator chk. sounds to me that the internal regulator or a diod is going bad.

Posted on Mar 04, 2009

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SOURCE: lights and fan blower motor speed decreases when idle steady

vachum modultor motor is leaking.

Posted on Jul 22, 2009

  • 11 Answers

SOURCE: Dim Headlights. 2001 Jeep

seems like a power issue, you could try buying a new battery or take it to an autozone and have your voltage checked battery should be putting out near 13 volts.

Posted on Aug 11, 2009

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SOURCE: 2000 Ranger 4.0 Automatic 4x4 will not idle up at

the idle air control could be faulty.

Posted on Dec 13, 2009

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