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CF Veteran
Joined: Sep 2010
Posts: 12,692
Likes: 6
From: Mercer County, NJ
Year: 2001
Model: Cherokee
Engine: 4.0L I6 HO
ok I'm at a loss here.
Here's my problem. Turn the Jeep on, voltage gauge reads 12ish. after a little bit drops all the way down and check gauges light comes on.
Jeep has a brand new Alternator and battery. The old Alternator tested positive as well.
When I first installed the new alternator it was at 14 volts where it should be. drove it for at least 2 hours, and then later that day drove it to my brothers an hour away. (probably not the smartest thing, but whatever). picked up a trailer full of junk. about 15 minutes in on my way back check gauges light comes on and voltage has dropped.
it's a 1998 so the voltage regulator is in the PCM/ECU or so I've read. tried another one, and same problem.
first thing I did was check the ground right next to the battery and it appears to be good.
any other ideas? Tomorrow my uncle is coming by with his fancy volt meter and electrical knowledge. Figured I'd post in here to try and get some other ideas.
Here's my problem. Turn the Jeep on, voltage gauge reads 12ish. after a little bit drops all the way down and check gauges light comes on.
Jeep has a brand new Alternator and battery. The old Alternator tested positive as well.
When I first installed the new alternator it was at 14 volts where it should be. drove it for at least 2 hours, and then later that day drove it to my brothers an hour away. (probably not the smartest thing, but whatever). picked up a trailer full of junk. about 15 minutes in on my way back check gauges light comes on and voltage has dropped.
it's a 1998 so the voltage regulator is in the PCM/ECU or so I've read. tried another one, and same problem.
first thing I did was check the ground right next to the battery and it appears to be good.
any other ideas? Tomorrow my uncle is coming by with his fancy volt meter and electrical knowledge. Figured I'd post in here to try and get some other ideas.
Do you have a spare PCM you can try out
Newbie
Joined: Aug 2013
Posts: 24
Likes: 0
Model: Cherokee
I replaced my alternator on my 1997 Cherokee and the jeep turns now but will not start up. It did with the old alternator. The battery is good I am almost 95% sure of that. I have probably been riding with a (going bad ALT) for a couple of months at least and I know starter is good. I know it has to be something way simple,,been raining here so hard to trouble shoot right now Any thoughts would help,,,,,,,,,,,,,,,,,,,,,,,Thanks
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
Salad, Kuzi said he tried that. If it isn't a grounding issue, battery and alt are known good, and PCM has been swapped, it sounds like a wiring issue to me. It isn't my specialty, but perhaps you have a bare wire in your harness?
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
I replaced my alternator on my 1997 Cherokee and the jeep turns now but will not start up. It did with the old alternator. The battery is good I am almost 95% sure of that. I have probably been riding with a (going bad ALT) for a couple of months at least and I know starter is good. I know it has to be something way simple,,been raining here so hard to trouble shoot right now Any thoughts would help,,,,,,,,,,,,,,,,,,,,,,,Thanks
Junior Member
Joined: Jul 2013
Posts: 86
Likes: 0
Model: Cherokee
CF Veteran
Joined: Feb 2012
Posts: 6,468
Likes: 18
From: Forest Hill, Maryland
Year: 1998
Model: Cherokee
Engine: 4.0L
wiring is what I was thinking as well. my uncle is an electrician and used to work on vehicles a lot in his younger days. (had a CJ7) so I'm hoping he can figure out exactly where the problem is.
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
Sorry, Nick! I should've known salad wouldn't make that mistake...
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
Junior Member
Joined: Feb 2014
Posts: 89
Likes: 1
From: VA
Year: 2000
Model: Cherokee
Engine: 4.0
ok I'm at a loss here.
Here's my problem. Turn the Jeep on, voltage gauge reads 12ish. after a little bit drops all the way down and check gauges light comes on.
Jeep has a brand new Alternator and battery. The old Alternator tested positive as well.
When I first installed the new alternator it was at 14 volts where it should be. drove it for at least 2 hours, and then later that day drove it to my brothers an hour away. (probably not the smartest thing, but whatever). picked up a trailer full of junk. about 15 minutes in on my way back check gauges light comes on and voltage has dropped.
it's a 1998 so the voltage regulator is in the PCM/ECU or so I've read. tried another one, and same problem.
first thing I did was check the ground right next to the battery and it appears to be good.
any other ideas? Tomorrow my uncle is coming by with his fancy volt meter and electrical knowledge. Figured I'd post in here to try and get some other ideas.
Here's my problem. Turn the Jeep on, voltage gauge reads 12ish. after a little bit drops all the way down and check gauges light comes on.
Jeep has a brand new Alternator and battery. The old Alternator tested positive as well.
When I first installed the new alternator it was at 14 volts where it should be. drove it for at least 2 hours, and then later that day drove it to my brothers an hour away. (probably not the smartest thing, but whatever). picked up a trailer full of junk. about 15 minutes in on my way back check gauges light comes on and voltage has dropped.
it's a 1998 so the voltage regulator is in the PCM/ECU or so I've read. tried another one, and same problem.
first thing I did was check the ground right next to the battery and it appears to be good.
any other ideas? Tomorrow my uncle is coming by with his fancy volt meter and electrical knowledge. Figured I'd post in here to try and get some other ideas.
IIRC, there is a small wire, (green?) Coming off the alt that goes to the PCM, if you ground that wire, the alt should go to full charge, if it does, then a faulty PCM.....RR
Last edited by Roadrunnr72; Feb 26, 2014 at 07:30 PM.