Voltage Drops at Stop

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Jan 8, 2011 | 04:31 PM

#16

XJx3

Member

Joined: Dec 2010

Posts: 243

Likes: 0

From: Central Indiana

Year: 1987,1990,1992

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by FrankZ

Nope, not in an XJ. The regulator is in the pcm.

Pre- 1991 are in alternator not PCM, they were all PCM 1991 and after.

Jan 8, 2011 | 04:37 PM

#17

Coach

Senior Member

Joined: Jan 2010

Posts: 536

Likes: 0

From: Lyons, Oregon

Year: 1991

Model: Cherokee

Engine: 4.0 HO

Quote:

Originally Posted by XJx3

Pre- 1991 are in alternator not PCM, they were all PCM 1991 and after.

Good to know, Thanks! Coach

Jan 8, 2011 | 05:21 PM

#18

Phatwitaph

Member

Joined: Dec 2010

Posts: 177

Likes: 0

From: Atlanta

Year: 1998

Model: Cherokee

Engine: 4.0

a good test for a dead or crappy alt is to crank it up disconnect that battery if the car dies it needs a new alt

Jul 29, 2012 | 05:38 PM

#19

xj4kids

Newbie

Joined: Jul 2012

Posts: 1

Likes: 0

From: St. Francis, Kansas

Year: 1999

Model: Cherokee

Engine: 4.0L

Quote:

Originally Posted by billfrank85

This same thing was happened to me at red lights. I would come to a stop, my engine would start running rough and my voltage would drop and sometimes it would die...I replaced the IAC sensor and it fixed the problem.

What is the "ICA sensor" or the "ASD relay"? Lol, having the same problem. XJ runs fine, voltage drops and stays low enough to create a concern on the problem until the next morning, when you drive to work for 10 minutes and start deccelerate, "voltage drops" again.....

Apr 22, 2017 | 03:46 PM

#20

AVjeeper

Seasoned Member

Joined: Sep 2009

Posts: 299

Likes: 12

From: Whittier, Ca

Year: 1989

Model: Cherokee

Engine: 4.0L

Voltage meter guage drops at idle

I just installed a upgraded 140 amp alternator and heavy gauge cable kit on my 89 Cherokee. Cable goes from alternator to battery. The voltage meter drops to 10-11 after the engine is warm and at idle like at a stop light. When accelerating and driving the volt needle goes back up to 12-14. No problems with dimming lights, etc.
I don't have a clue.
AVjeeper

Apr 22, 2017 | 06:59 PM

#21

BlueRidgeMark

CF Veteran

Joined: May 2012

Posts: 7,965

Likes: 964

From: Lost in the wilds of Virginia

Year: 1998 Classic (I'll get it running soon....) and 02 Grand

Model: Cherokee (XJ)

Engine: 4.0

Read here and here.

Apr 22, 2017 | 07:11 PM

#22

moparado

Senior Member

Joined: Jan 2017

Posts: 799

Likes: 4

From: usa

Year: 2000

Model: Cherokee

Engine: 6 cylinder

Get a voltmeter and measure the voltage at the battery terminals at idle.
That will tell you if your dash gauge is accurate or maybe your alternator is kaputt.

Only other thing i can think of is a loose slipping belt trying to drive the alternator pulley at idle rpms'.

Apr 23, 2017 | 10:38 PM

#23

nujeepguy

Banned

Joined: Oct 2016

Posts: 1,553

Likes: 4

Year: 2000 and 1998

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by Phatwitaph

a good test for a dead or crappy alt is to crank it up disconnect that battery if the car dies it needs a new alt

i hear thats dangerous, they say alt needs the batt load, volts could spike? seems like regulator would hold it but i wouldnt try that.

Apr 24, 2017 | 12:52 AM

#24

fb97xj1

CF Veteran

Joined: Dec 2015

Posts: 3,038

Likes: 338

From: PA

Year: 1997

Model: Cherokee

Engine: 4.0L

You should never disconnect the battery with the engine running on a computer controlled vehicle. The battery acts as a buffer for the alternator. Without the battery, the voltage regulator spikes (ive read as much as 150v) and you run the risk of frying the computer, among other things. And no, the voltage regulator may not be fast enough to stop it.