Headlights Dimming When Using Power Windows???

[osargd]

At night when I have my headlights on I’ve noticed that if I use my power windows my headlights will dim. I haven’t said anything to my passengers to see if they notice and most do not, my buddies who are ‘gear heads’ pick it up immediately though so I know I’m not crazy. This isn’t a huge problem, but its one of those things that kinda annoys a conscious Jeep owner.

Anyone else notice this problem?

Any suggestions?

I’m thinking of getting one of those high power Optima batteries… any feedback on them? Will one of these solve my problem?

[Elt31987]

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.

[autoboy454]

could be battery OR alternator related

[Busch2fan]

I'd have the alternator and battery checked at AutoZone or one of those places with a full load.

[ColdCase]

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?

[adidasf50soccer]

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.

[liquidxit2]

Usually the voltage regulator on the alternator. The alternator can put out spec like voltages with this problem.

[99xjjoe]

This is usually normal

[PhotograJeep]

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
proceeding

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.

[LibertyTC]

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.

[95BadBoy]

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.

[LibertyTC]

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.

[PhotograJeep]

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?

[PhotograJeep]

bump. anyone tried the capacitor idea? i would think that it would reduce consumption a tad as well.

[ColdCase]

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.