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Old 01-31-2006, 12:14 AM   #1
Scooby Newbie
Member#: 88680
Join Date: Jun 2005
Default Lights dim and blower slows :(

Driving my car home lastnight I noticed that about ever 3-4 minutes my lights were dimming and the blower motor would slow. This would last for about 10-15 seconds then the lights and blower would kick back into normal power. Anyone know what this is and how to fix it??

2003 wrx sedan 5spd 52k
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Old 01-31-2006, 01:16 AM   #2
Scooby Specialist
Member#: 2159
Join Date: Aug 2000
Chapter/Region: SCIC
Location: Fullerton, CA
2004 WRX
Some semblance of Silver


You using full defrost?

Mine does that in the mornings with full defrost & the rear defogger going.

2004 Sedan, 56k.. old battery maybe?


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Old 01-31-2006, 09:53 AM   #3
Scooby Newbie
Member#: 82662
Join Date: Mar 2005
Location: Toronto
00 2.5RS Sedan


This could be due to a large current draw on the electrical system (stereo, lighting, accessories...). Might be battery or alternator. Have them tested to be sure which before you start replacing stuff.
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Old 01-31-2006, 09:58 AM   #4
drivin blind
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Member#: 73043
Join Date: Oct 2004
Chapter/Region: MWSOC
Location: Carson City, Michigan
2011 STI/2010 370Z
Black/Black Cherry


Mine does the same. I can really notice it when at idle with defrost on and fan up on 4. Don't think it's the battery, just the alternator not spinning fast enough. Actually my 96 Cherokee did the same at idle and that had the off road package including a large alternator. I wouldn't be concerned unless you battery seems to be weak on start-up.
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Old 01-31-2006, 07:33 PM   #5
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Member#: 88680
Join Date: Jun 2005

na my battery is good ( 1 month old optima) I'll test the alt. Thanks
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Old 01-31-2006, 07:57 PM   #6
Trust no one
Member#: 11170
Join Date: Oct 2001
Chapter/Region: Tri-State
Location: NYC
02 WRX
15 WRX/05 GTO


If you have the HVAC in one of the defrost modes the AC compressor will run, even though the AC light remains off. When the compressor cycles on at idle you may see the lights dim. It will be more noticeable if you are maxing out the alternator by having a lot of things running such as lights, rear defrost, brake lights etc.
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