Headlights Dimming When Using Power Windows??? - JeepForum.com

LinkBack Thread Tools
post #1 of 15 Old 11-19-2009, 07:00 AM Thread Starter
Registered User
2004 KJ Liberty 
Join Date: Nov 2009
Location: Saratoga, NY
Posts: 26
Headlights Dimming When Using Power Windows???

At night when I have my headlights on Iíve noticed that if I use my power windows my headlights will dim. I havenít said anything to my passengers to see if they notice and most do not, my buddies who are Ďgear headsí pick it up immediately though so I know Iím not crazy. This isnít a huge problem, but its one of those things that kinda annoys a conscious Jeep owner.

Anyone else notice this problem?

Any suggestions?

Iím thinking of getting one of those high power Optima batteriesÖ any feedback on them? Will one of these solve my problem?

GDO - 04' Liberty
osargd is offline  
Sponsored Links
post #2 of 15 Old 11-19-2009, 08:01 AM
Senior Member
Elt31987's Avatar
2008 KK Liberty 
Join Date: Mar 2009
Location: Stoneham, Massachusetts
Posts: 945
Ive noticed this on all my cars and my Jeep and my friends 07 Sentra does the same. Sometimes on his also using the power window the RPMs will drop from like 1100 to 900 for a second.

2008 KK Liberty
Inferno Red
Daystar 2" Spacer Lift With SkyJacker Hydro Shocks
JBA Gen 5.5 Upper Control Arms
Rokmen Riddler 8.25 Differential Cover
2 KC Slimlite 100 Watt Driving Lights on JK Light Bar
245/75/16 All Terrains
Mopar Front Tow Hooks
Mopar Rear Tow Hook
Mopar Skids
Elt31987 is offline  
post #3 of 15 Old 11-19-2009, 08:11 AM
Registered User
1989 YJ Wrangler 
Join Date: Oct 2009
Location: Hatfield
Posts: 397
could be battery OR alternator related

Love to wheel? Live in/around Massachusetts? Check us out!
autoboy454 is offline  
post #4 of 15 Old 11-19-2009, 09:22 AM
Registered User
2008 KK Liberty 
Join Date: Mar 2008
Location: Temperance, mi
Posts: 187
I'd have the alternator and battery checked at AutoZone or one of those places with a full load.
Busch2fan is offline  
post #5 of 15 Old 11-19-2009, 09:49 AM
My Reality Check Bounced
ColdCase's Avatar
2011 WK 
Join Date: Sep 2009
Location: New England
Posts: 8,301
This is usually a sign of a battery getting weaker, corroded power connections, or a weak ground either at the battery or at the window motor. Poor connections cause more current to be drawn. Usually the alternator is not sized to keep completely up to all conceivable current loads, and the battery makes up for any short term deficit. How old is the battery? Do you get flare coming off idle (lights dim at idle but are brighter at a higher rpm). Roll up and down the window while Autozone is testing to see if they notice any unusual fluctuations.

Depending on how old the battery is, it may be easier to clean the battery connections and, if the problem persists, just replace the battery. If the problem still persists, then you are probably looking for poor connections, usually a ground. But a weak alternator or bad regulator could also cause these symptoms. You may be able to quickly sort out a bad ground by using a voltmeter to check if there is a voltage between the negative battery terminal and a good chassis ground. Do all the window motors dim the lights?
ColdCase is offline  
post #6 of 15 Old 11-19-2009, 11:52 AM
Registered User
2005 KJ Liberty 
Join Date: Sep 2009
Location: Pittsburgh
Posts: 4
I've noticed that mine do the same thing. I'm gonna have to get my battery checked, because I notice that my headlights dim even when using just one power window.
adidasf50soccer is offline  
post #7 of 15 Old 11-19-2009, 11:57 AM
Registered User
2002 WJ 
Join Date: Sep 2008
Location: Dixie
Posts: 1,082
Usually the voltage regulator on the alternator. The alternator can put out spec like voltages with this problem.

2002 Jeep Grand Cherokee Limited 4.7 low output quadradrive. 31in General Grabber AT2, OME HD, bilstein 5100, IRO sway links, addco rear sway. Kolak 3in exhaust with flowmaster SUV 50, magnaflow 3in cat, Custom K and N FIPK, modded airbox with ram air, Fastman 71mm Throttle body, PML RFE Deep pan, Autometer digital trans temp gauge, P.I.E. aux adapter, Infinity reference 3.5/6x9/6.5, 200w inverter, surco rack, front/rear/cargo husky liners.
WJ Build!
liquidxit2 is offline  
post #8 of 15 Old 11-20-2009, 12:44 AM
Registered User
1999 XJ Cherokee 
Join Date: Mar 2009
Location: lakemoor, ill
Posts: 386
This is usually normal
99xjjoe is offline  
post #9 of 15 Old 11-20-2009, 06:35 AM
Registered User
2008 KK Liberty 
Join Date: Aug 2009
Location: Jackson, TN
Posts: 67
it may be normal, however, if it is a significant dimming, you may want to really look hard at your connections. when it comes to battery and alternator, it can be difficult to determine the chicken or egg.

Battery State of charge: (Engine OFF) always remove surface charge from batteries. To do this
either, attach a carbon pile and load the batteries at 25% of the total CCA rating for 15 seconds or switch the
headlamps on; select high beam for 2 to 3 minutes per battery, then switch off head lamps. Allow the batteries
to recover for 30 seconds, then test the batteries true state of charge with a volt meter. When surface charge
has been removed and battery voltage is found to be below 12.40 volts, charge or replace batteries before

Battery voltage verification at alternator terminals. Ensure that battery voltage is present when
measured at the alternator positive (+) and negative (-) output terminals and between the negative (-) and
“S” Remote Sense Terminal. This should be inspected with the engine off and all electrical accessories in the
off position. This voltage should be the same as battery voltage measured in the above step. If the volt meter
indication is .50 volt less than battery voltage, complete individual cable voltage drop test on the positive and
negative cables. Correct voltage drop before proceeding.

Alternator voltage test. Connect the test leads of a volt meter to the alternator output terminals. Note:Most alternators have isolated ground rectification. Always connect tester / volt meter
directly to the negative output terminal of alternator or your test will be inaccurate.
• Start engine, increase to high idle (1500 RPM): The volt meter should now indicate that the alternator
output voltage has increased to a range from 13.8 volts to 14.2 volts. (Ensure that all electrical accessories
of the vehicle are in the off position.) If voltage increases but is out of range, inspect to see if alternator has
an adjustable regulator. If so, reduce engine speed to idle and adjust voltage to a setting of 14.0 volts. If
voltage is higher than 14.7 volts and cannot be adjusted below 14.25 volts, or if voltage is lower than 13.8
volts and cannot be adjusted into range then replace alternator.
• Inspect if voltage does not increase: If the alternator incorporates an ignition (IGN) terminal this
terminal must have battery voltage present above 12.4 volts. If not; inspect circuit for open and
repair. If all is verified and alternator voltage has not increased or is out of range replace alternator.

Performance Test. Set engine speed to 1500 RPM.
• With either a carbon pile or with truck accessories apply a current load equal to 75% of rated output capacity
of the alternator and maintain load for 5 to 10 seconds (see box 4 below). Test voltage after 10 seconds
with a volt meter at the alternator output terminals (enter voltage into box 5 below) If truck accessories are
utilized for current loading this must be monitored with an inductive current device on the positive output
cable of the alternator. (Note applying a load greater than 80% of rated output capacity of alternator
will cause the test to be inaccurate.)
• Properly functioning alternators will have a voltage drop of no more than .50 volts from no load to
loaded states (see value from box 6 below). If the voltage drops more than .50 volts the alternator
is considered to be defective.

Hope all of this helps you. If you do not understand a little in here, I or someone may be able to help.

Photographer and Jeeper, Ken. 08 KK Custom Crossbars.
PhotograJeep is offline  
post #10 of 15 Old 11-21-2009, 10:52 AM
Registered User
2004 KJ Liberty 
Join Date: Sep 2008
Location: Vancouver B.C.
Posts: 907
Wow PhotograJeep that is some great testing information !
Ok so I also own an 04 that has the lights dim when windows motors used.
I think Jeep should have not cheaped out and supplied a puny 600CCA battery in the first place.
For the equipment and draw of KJ an 800 CCA battery should be considered minimum requirements.
So back to osargd question, would "one of those high power Optima batteries" help ?
Find any new battery rated at 800 or greater CCA (cold cranking amp) rating.
If you want the very best battery and don't mind spending the dollars for a battery that is way more powerful than an Optima, get one of these:
ODYSSEY Batteries - Official Manufacturer's Site
I doubt when one of these are installed if any, or much dimming would take place again.
Better Grounding/thicker negative wires in the KJ would also be a "BIG" improvement, that is a topic for another day.
LibertyTC is offline  
post #11 of 15 Old 11-21-2009, 02:33 PM
2005 TJ Wrangler 
Join Date: May 2006
Location: Grand Forks, ND
Posts: 3,006
There are a lot of bad connections / grounds that get diagnosed as bad batteries. So do look for bad connections, many need to be removed, cleaned and reinstalled as there are a lot that don't get seen by just a very brief inspection. FWIW

Liberty TC

Those batteries do rock !! Sears Platinum is made for them by Odyssey.

05 TJ RME 42RLE with some things
05 KJ CRD 545RFE, GDE Eco tune, Franky II, Al's 4.5 A-arms, JK Rubi Moabs, Silent Armors 245-70-17's, Spidertrax Adapters, Rola Basket, Fumoto Valve, Pinch welds pounded - Sold 2015
95BadBoy is offline  
post #12 of 15 Old 11-21-2009, 03:08 PM
Registered User
2004 KJ Liberty 
Join Date: Sep 2008
Location: Vancouver B.C.
Posts: 907
Yes I had heard that..I checked a few weeks ago and unfortunately....
Too bad all of the Automotive departments at our Sears stores are gone. No Sears batteries to be had in B.C. Canada.
Wonder if I could get one up from Bellingham somehow? the price of the Odyssey's are like $400 locally.
My current stock Chrysler battery is only a year old..so still time to find something good but really for long term, best to save for an Odyssey..big period.
LibertyTC is offline  
post #13 of 15 Old 11-22-2009, 08:13 AM
Registered User
2008 KK Liberty 
Join Date: Aug 2009
Location: Jackson, TN
Posts: 67
2 mods that can be done... add a higher capacity battery for large loads. get a higher capacity, higher performance alternator (this helps when towing or using larger loads). also, a capacitor isn't usually considered, but that will probably get rid of your dimming problem as well. 1 farad audio capacitors would be a good addition. Anyone disagree?

Photographer and Jeeper, Ken. 08 KK Custom Crossbars.
PhotograJeep is offline  
post #14 of 15 Old 11-28-2009, 04:31 PM
Registered User
2008 KK Liberty 
Join Date: Aug 2009
Location: Jackson, TN
Posts: 67
bump. anyone tried the capacitor idea? i would think that it would reduce consumption a tad as well.

Photographer and Jeeper, Ken. 08 KK Custom Crossbars.
PhotograJeep is offline  
post #15 of 15 Old 11-28-2009, 05:04 PM
My Reality Check Bounced
ColdCase's Avatar
2011 WK 
Join Date: Sep 2009
Location: New England
Posts: 8,301
1 farad won't have enough capacity at DC, and with current capacitor technology in that size, could easily explode if internal leakage develops. Higher voltage rated smaller capacitors do absorb RF noise that interfere with the radio however and are much safer. Stereo nuts often add 1 farad caps to their amp power feeds to help get them over temporary power deficiencies, but they are mounted close to the amp so they don't have to deal with the resistance of long wires. 500 watts are basically their limit... and they cost $80-$100 each.

The battery itself actually acts like a large DC capacitor. So just add a second battery, more capacity for about the same $$... but that could lead to more problems when one fails. So the most practical method to increase capacity is to go to a larger battery, one rated for more short term current.

I have two batteries in the RAM for starting, but they are otherwise isolated I think.

Last edited by ColdCase; 11-30-2009 at 08:17 AM.
ColdCase is offline  

Quick Reply

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
2002 Rear Power Windows Inoperative Brighton Jeeper KJ Liberty Forum 7 04-01-2016 02:39 PM
Power Windows Seized XtremeCuztoms KJ Liberty Forum 0 09-12-2006 07:41 AM
Auto Dimming Mirror Noise aujeep KJ Liberty Forum 2 02-25-2006 10:07 AM
HEI Headlights belezeeubub KJ Liberty Forum 4 11-19-2004 01:38 PM
Dimming Dash Lights valvestem KJ Liberty Forum 2 07-08-2004 04:38 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome