Battery light when WOT

[Tellreded]

My battery light pops on whenever I go to a higher RPM. At night time, I notice that as my RPMs get higher, all lights get dimmer. I'm thinking it might be the voltage regulator. Would anyone know how to fix that?

Vehicle - Jeep liberty
Year - 2006
Trim - limited 4x4
Engine - 3.7L

 

[ltd02]

The voltage regulator is integrated into the PCM in these things.

Mine did this years ago until the alternator completely failed. Measure the voltage at the battery while it is idling. Should be a bit over 14volts.

Interesting thread here: http://www.jeepkj.com/forum/f196/external-voltage-regulator-not-59390/

 

[renegade 04]

if the lights get dimmer I would tend to think your alternator maybe on its way out. If you do decide to replace the alternator try and get a Denso alternator, its also known to many as the 160 amp alternator.

 

[Rsb563]

Third the alternator.

 

[JasonJ]

Indeed, alternator. You see this when at higher rpm the brushes start to short out against the stator as it spins faster... think centrifuge.... then they touch the outer casing or the stator itself.

 

[Tellreded]

The alternator is 2 months old. And if the regulator is in the pcm, does that mean that I have to replace the whole pcm? I don't really wanna pay $250 to fixe a $10 part

 

[HoosierJeeper]

What brand of alternator did you get? Non OEM ones are known to have ****** life spans. I got a junkyard one with 60k miles for $50, I got 160k out of my stock one so I figure $50 for another 100k isn't a bad deal.

 

[Tellreded]

Publitech 12-93 rev00

 

[Tellreded]

I will test battery with a volt meter when I get home. Battery when engine on, immediately turned off and 5 mins later. I'll also do one with the engine at 3000-4000 rpms

 

[LibertyTC]

At idle here is a good charging voltage...

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Always try to replace alt with the correct model/ Denso. This one is for NON Renegade Models.
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Curious-How old is your battery? Had it load tested lately, fall is a good time to be checked.
Does it have removable distilled water caps, or is it sealed? link below for removable cap type batteries.
http://www.jeepkj.com/forum/f202/maintain-check-your-lead-acid-battery-removable-caps-47021/

 

[Tellreded]

That's actually a really good idea, I'll throw some de-ionized water in the battery and see if that does anything. Also, the age of battery is unknown. My uncle sold me this jeep cause he didn't have the time to fix the abs c1020 code

 

[Tellreded]

I just got a daignostics code reader. Says an error is present. The code has to do with the generator field control. I also watched my voltage while driving and it goes down as the load goes up, dropping to as low as 8 volts. Idling, it's at around 13.8 and same with driving around nicely.

 

[ltd02]

13.8 is low at idle. Should be 14.3 or so. Sounds like it's alternator time.

 

[tjkj2002]

13.8 is low at idle. Should be 14.3 or so. Sounds like it's alternator time.

Anything above 13.2v is good.

The hotter the alternator get's the less voltage it will put out.

 

[ltd02]

Interesting. I knew about heat and less output but I've still never seen below about 14.2 even when "hot". I've measured after my 40 mile commute in the summer in MD. I'll have to try it again sometime and see. Haven't done this on my 05 yet. :gr_grin:

 

[tjkj2002]

Interesting. I knew about heat and less output but I've still never seen below about 14.2 even when "hot". I've measured after my 40 mile commute in the summer in MD. I'll have to try it again sometime and see. Haven't done this on my 05 yet. :gr_grin:

Stone cold start up my KJ will put out 14.8 volts,but it also idles between 800-1000rpm,once at actual idle it's about 14.5 volts.After driving for some time it will be between 13.6 and 14 volts depending if I'm using AC or not(to include defrost).

 

[profdlp]

...I also watched my voltage while driving and it goes down as the load goes up, dropping to as low as 8 volts. Idling, it's at around 13.8 and same with driving around nicely.

Mine did the same thing and a new battery took care of it. Don't just buy parts yet, though. Get it all tested first.

 

[Billwill]

Unlikely the PCM is faulty...most likely the brushes inside your alternator have worn down.

Are the drive belt and idle bearings OK...check with the A/C turned on.
Check the routing of the cables from the Alternator to the battery and to the PCM to check for any fraying to the engine or chassis.

Always worth checking that the battery is good and that the battery connectors, negative battery strap to chassis and the grounding straps grounding engine to chassis are all clean and tight.

 

[Tellreded]

Unlikely the PCM is faulty...most likely the brushes inside your alternator have worn down.

Are the drive belt and idle bearings OK...check with the A/C turned on.
Check the routing of the cables from the Alternator to the battery and to the PCM to check for any fraying to the engine or chassis.

Always worth checking that the battery is good and that the battery connectors, negative battery strap to chassis and the grounding straps grounding engine to chassis are all clean and tight.

I'm thinking it might be the belt then, cause I'm fairly certain the alt is good as it's only 2 months old and when the power is lost, it shoot right back up in less than half a second. I don't hear any squeeling though from the belt so I really have no idea. And I can't get the battery tested as I feel it would be a waste of money. (It's around $200 here)

 

[JasonJ]

I'm thinking it might be the belt then, cause I'm fairly certain the alt is good as it's only 2 months old and when the power is lost, it shoot right back up in less than half a second. I don't hear any squeeling though from the belt so I really have no idea. And I can't get the battery tested as I feel it would be a waste of money. (It's around $200 here)

Don't assume that just because a 2 month old part is only 2 months old that it hasn't gone bad.

You can't buy a carbon load tester and test the battery yourself? Any auto parts store should sell them, if they don't offer free diagnostic testing there. It's a battery ... you're not having DTC's diagnosed, or an MRI being performed. Lol.

Literally, any of these will do. The $20USD ones are fine:

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https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=battery+load+tester

The waste of money will be when you throw parts at it that the vehicle never needed. Do this methodically and you'll be alright.