9-10 volts with ignition on gradually decreases from 14 after start up - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > 9-10 volts with ignition on gradually decreases from 14 after start up

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineAdvance Adapters SYE KitsCustom Axle Work at CCOR

Reply
Unread 01-16-2014, 04:36 AM   #1
inkspot88
Registered User
1993 ZJ 
 
Join Date: Jul 2012
Posts: 96
9-10 volts with ignition on gradually decreases from 14 after start up

This may be a long one... As the title states when I turn the ignition on my voltage gauge reads anywhere from 9-10 volts but it fires right up. Never skips a beat. Upon start up in the morning it reads 14. As I start it more throughout the day it decreases to a low point of about 11 with nothing but the radio on. If I turn on heat it drops a little lower and continues with more with lights, wipers etc. So yesterday I broke out the multimeter. Battery read 12.6 on multimeter iirc, around 10 on gauge. Started it up...read 13.4 on meter, gauge read around 12. Turned fans on highest setting, high beams, radio turned up (also have amp/sub on) wipers on high, rear defroster and the gauge dropped below 9. No cel, no stalling or sputtering. Only thing I noticed was the wipers slowed a bit (happens when real cold too). Reading at the multimeter stayed steady. Shut the engine down left the lights on a few minutes then turned them off and waited a few minutes. Checked reading at the battery cable on the power distribution center and the body body ground, 12.6. Checked it at the starter, 12.5. So the questions I have are... what other test can I perform to check impedance of the cables, does what sends info to gauge also send it to pcm or is it separate which would explain why I have no cel but gauge reads bad. Could something wrong between gauge and switch or could the gauge just be a liar. This has been happening since I bought the jeep in July 2012. I have replaced alternator with 136a and put in a new battery in Dec 12. It is a 93 5.2. If the gauge is reading right and I am loosing that many volts between where I've tested and it, I would like to see it fixed so it doesn't die on me at some very inconvenient point. One more thing is I had all those accessories on for over a minute with the gauge reading below 9v. Feel like the engine would have had trouble with that low of a current for that long. Ok I lied one more thing... no battery symbol light on the dash bit I've never seen it on this vehicle so the bulb could just be out for it (I have a couple others that are out). Thank you for reading this very long post.

inkspot88 is offline   Reply With Quote
Unread 01-18-2014, 09:37 AM   #2
Oldfrog
Web Wheeler
1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 3,906
A couple of things come to mind, but I know nothing about the 5.2, so bear that in mind...
1. On the 4.0, the voltage regulator is in the PCM. It could be heating up and going bad.
2. You might have a slight short to ground somewhere. It's heating up, making better contact as it does so, and pulls your voltage to ground. ( just a theory)
3. You got a bad alternator. It happens. But I'm guessing maybe a bad connection at the alternator or engine ground.

That's all I have before my second cup of coffee this morning. Hope it helps !
__________________
Cajun Recipes and Fishing tips

Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
Oldfrog is offline   Reply With Quote
Unread 01-18-2014, 10:27 AM   #3
Timer96
Registered User
1996 ZJ 
 
Join Date: Dec 2013
Location: Sacramento, CA
Posts: 64
here ya go

https://www.youtube.com/watch?v=paw80mS_Kxg

edit to change the vid, the guy in the first one wasnt helpful.

a voltage drop test can be done on any circuit, not just the starter

Last edited by Timer96; 01-18-2014 at 10:39 AM..
Timer96 is offline   Reply With Quote
Unread 01-18-2014, 04:15 PM   #4
inkspot88
Registered User
1993 ZJ 
 
Join Date: Jul 2012
Posts: 96
My first thought was the alternator. Replaced it. Also replaced the pcm as my second guess. Both were very old and the pcm was throwing random codes anyway. Should have put that in the first post but when I wrote it I had been up for 22 hours. I will have to look for the small ground that theory makes a lot of sense. And thanks for that link. This is my first attempt at tracking down electrical issues. I'm going to get back out the meter and test everywhere I can.
inkspot88 is offline   Reply With Quote
Unread 01-22-2014, 12:46 PM   #5
SuperStew11
Registered User
2000 WJ 
 
Join Date: Mar 2013
Posts: 184
I'm having the same issue, just put a brand new alternator on today, fires up reads 14v on gauge same on multi reader, then gauge drops to 10-11 on the gauge with a 12.6 reading

Start driving around it stays at 13-14 on the gauge until I stop and idle and then it drops
SuperStew11 is offline   Reply With Quote
Unread 01-23-2014, 10:29 PM   #6
inkspot88
Registered User
1993 ZJ 
 
Join Date: Jul 2012
Posts: 96
Yea I still haven't been able to figure this out. If I hook up cables to jump it my gauge reads right under 14. Take them off and back to 9.5ish with the battery on. Driving this morning I noticed it was at 12 at a stop light, then I turn on my rear defroster boom down to right above the red line on the gauge and my headlights dimmed. Where else should I do a voltage drop test besides to the starter and fuse box under hood? Where does the voltage reading come from?
inkspot88 is offline   Reply With Quote
Unread 01-24-2014, 12:57 AM   #7
Oldfrog
Web Wheeler
1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 3,906
Autozone alternator? I've gotten a bad one before.
__________________
Cajun Recipes and Fishing tips

Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
Oldfrog is offline   Reply With Quote
Unread 01-24-2014, 03:04 AM   #8
inkspot88
Registered User
1993 ZJ 
 
Join Date: Jul 2012
Posts: 96
Swapped it. Old alternator did the same. Swapped pcm still the same. Rear defroster and the windshield wipers seem to be the killer. Still looking for something that could be grounding out somewhere.
inkspot88 is offline   Reply With Quote
Unread 01-24-2014, 12:41 PM   #9
Pierre_r
Senior Member
 
Pierre_r's Avatar
1989 XJ Cherokee 
 
Join Date: Jul 2009
Location: Sweden
Posts: 542
Dont trust the voltgauge in the instrument. Its not that accurate to tell you exactly what the alt is charging.
Mine has a life on its own sometimes some days it will read over 14V all day, the next it will only go to the line that is before 14V and stay there all day...

If your voltmeter says its charging over 13V (but not over 14V) when you measure across the battery the alternator is ok.
Pierre_r is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.