Ok. I was driving and my check gauges light came on I noticed my volt gauge was at zero. Jeep never died or started cutting out like it was loosing voltage. So I figured it was a bad alt.. I can't really diagnose much as I just had singer and am on crutches... I swapped the alt out and am still having the same issue. It will read no volts and them randomly 12v but never 14v like it would read if it was charging... I have checked obvious things like batt cables and the plug and wire connection on the back of the alt. Any input would be great! This is on an 01 Xj. Thanx!

 

I dunno bud I would start cleaning grounds.... also clean fuses.. definitely start it up and check voltage at the battery... if bats good you know your charging... maybe the gauge is going bad.

 

Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea!

You can't just check or look at these grounds. You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. Start with the one on the back corner of the head, and where it attaches to the firewall, as that braided line often deteriorates over time and is susceptible to damage. Scrape the paint from the firewall. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support. Scrape the paint off first.

 

Ok I will have a buddy check and do all those things today and see if it fixes my issue. I figure it to be a ground issue but just wanted some other more knowledgeable input. Thank you. And i will post back asap.

 

Ok I managed to check and see if the alt is charging and it isn't I'm just reading batt voltage actually just under I was reading 11.6 with it runnin... So my next question is what could cause this? Still a ground issue or something else. I'm runnin to the parts store to get ground cables in. Lil but and I have a busy who is gonna put them on the way that was mentioned and clean all the other... Any other ideas?

 

Anyone?

 

Chances are you got a bad alternator. But did you carefully check continuity between all your connections to the alternator? If those are good check to make sure the excitor wire (the little one telling the alternator to charge) has voltage.

 

I read a thread on here sayin that my non charging issue could be a bad PCM causing this issue? Is there any truth to that???

 

The alternator is brand new I just put it on 2 day ago and it didn't fix my issue. Now the excite wires are the 2 on the small plug coming from
The PCM. Should the be 12v? If I'm not getting anything there is that a bad PCM? According to the wiring diagram both o those wires come directly from the PCM. One is says it's a generator source and the other is generator field.

 

I would do the grounds first. double check all your connections between the battery and alt

 

Most definitely check the grounds and check for deteriorated/damaged wiring. The alternator should always be checked at the alternator first...then at the battery (to make sure the connecting wiring is sound). If you check the alternator at the contact and don't get 14v, you know its your alternator.
I concur wholeheartedly with tjwalker...a good ground cleanse periodically will a lot of times solve whatever electrical problem ails ya!

 

Ya sounds like the alt isn't being activated. Should be 12v.... if you checked on a known good ground then you might be looking at pcm. You could try jumping it from a keyed source. Ny ecu is bad to tos so I sliced into the map (most related sensor) and its working great.

 

I just tested the voltage on the two wires goin to the alt. On read battery voltage which is kinda low It read 11.6 and tw other wire was a ground. I'm unsure which is which cuz the diagram I looked at didn't give wiring colors. So I am getting voltage on one of the wires. Also the output on the alt post is also batt voltage at 11.6 and then the batt itself reads 11.6 so from what I'm seeing is that the alt isn't charging I'm just unsure why. Also the volt gauge in the cluster will read no voltage and the check Gaye light will come on and then periodically it will read batt voltage with like mentioned is around 11.6. Any ideas?

 

Also this jeep is very clean under the hood and it hasnt been hacked up or abused the wiring is real clean not rotted or hacked up. It has a yellow top optima in it it was in there when I bought it could this be a bad battery?

 

You should at least have voltage at the output post on the alternator when running 14+.... if you have power going in and nothing coming out I would say pull it and have it tested at the store you bought it at. A lot of "new" alternators are remanufactured.. depending on what you got it can be a crap shoot. No matter what if you have power to the excitor and ground out should have output. Before you pull it though you might try charging Try battery up to full. That may het it working.