Voltage drops more than I'd like at idle

[N8N_99xj]

Does this sound like a bad diode or diode(s) in the alternator or something else? Can't really throw an oscilloscope on it as I only have street parking and my only scope is a full size benchtop one.

I'm considering rebuilding the alternator myself, if I can find the parts, because I'm bleeding cash.

Where can I find parts or failing that a replacement alternator? I have a 2001 4.0 and build sheet says 124 amp alternator but I can only find ones listed as "117 amp" or "Nippondenso" (and I have no idea if I have a Nippondenso alt. or not; I don't see a label on it.)

Unrelated, why do I have a Limited but the build sheet says Classic? Weird.

 

[RCP Phx]

The alternator "regulation" is controlled by the ECU so I would check that wiring first!

 

[N8N_99xj]

Also, the cables look good but the battery terminals have been cut off and universal ones clamped on to the old cables. Would it be wise to replace them with something like a Big 7 kit before going nuts? I remember putting new cables from Jon Kelley on my first XJ and I had no problems with it until the alternator literally seized up from a leaking radiator.

 

[RCP Phx]

As long as there is no corrosion in the cables I would say that's a non-issue, are you running a wet cell battery?

 

[N8N_99xj]

As long as there is no corrosion in the cables I would say that's a non-issue, are you running a wet cell battery?

Sadly yes, I had an Optima and then an AGM but this one has a near new Interstate battery in it, so I can't justify replacing it.

Everything looks pretty clean, I just don't like those repair ends. It's also been miserably hot for like 2 months straight so I can't stand to be outside turning wrenches or troubleshooting a lot.

 

[N8N_99xj]

Now that I think about it, the starter seems a little draggy so perhaps I should pop for the cable kit.

I will take your advice and Deoxit the small wire connections on the alt, and also the ECU. I was actually meaning to ask if this was one of "those" alternators.

Odd thing is the one battery cable on my first XJ was literally hanging on by one strand when I got it but it started fine in freezing temps in PA and OH several times when I drove it home, and I noticed no charging issues either.

 

[Unclewolverine]

Are you just going off the gauge or a volt meter? The gauges are notoriously unreliable and inaccurate.

 

[lawsoncl]

Measure right at the battery with a meter and see if it's good.

 

[N8N_99xj]

So I finally doubled back to this as it's hot as heck so now my e-fan is running a lot and I'm running the A/C again

stopped at a light a couple miles from home and the volt meter dropped all the way to 9 and check gauges came on

when I got home I popped the hood and checked it with my Fluke, with dash gauge reading 12 the Fluke read 12.7 so... not great

Unfortunately I cannot clean any of the connections now as I'll burn the (redacted) out of my hands. I guess the order of ops is to clean the plugs at the alternator and the PCM and if that doesn't sort it... remove the alternator and have it tested? Buy a new battery cable kit? What do you think is most likely?

If it is the alternator, where can I get a good replacement? I can't find a "124 Amp" alternator anywhere.

Also, small annoyance - does anyone sell a replacement clip to hold the prop rod?

 

[RCP Phx]

Have you tested the battery with a load tester?

 

[N8N_99xj]

Battery looks to be brand new, so no. I'm still unpacking from a move, so if you ask me WHERE my load tester is...

 

[Bent]

As long as there is no corrosion in the cables I would say that's a non-issue, are you running a wet cell battery?

In, yes. Been bit by that hound. Everything looked fine at the connection.

ETA: Electrolyte levels good?

 

[Tim_MN]

9 volts on the OBD-II voltage gauge typically signals a faulty alternator, most often the brushes are worn out. The alternator should be charging at 13.8-14.4 volts. 19 volts on the voltage gauge typically indicates a connectivity issue in the charging system. Often loose wires or corroded connections.

If you buy a rebuilt alternator, have it tested before you leave. 10-15% of Chinese rebuilt alternators are defective right out of the box.

I prefer to have my alternators rebuilt locally using Japanese or German parts.

 

[N8N_99xj]

Where can I find a rebuilt alt though? Build sheet says 124A and I can't find one anywhere. I've searched and found others asking similar questions with no resolution.

 

[N8N_99xj]

It was really acting up today... I think I need to address this sooner rather than later

this place lists only one alternator for my vehicle

Alternators for 2001 Jeep Cherokee | Mopar Online Parts

parts.moparonlineparts.com

if I look up 56041822AB though everyone lists it as "117A" not "124A"

More Information for REMY 94675

I guess it's the same thing? I took a pic but it looks like I can't attach

Also, if I do this, where can I buy good rebuild kits? Def. will rebuild and keep the old one

I was going to change the fan clutch anyway, if I have to take the belt off I'll just change the alt. and be done with it.

 

[Bent]

Alternators for 2001 Jeep Cherokee | Mopar Online Parts

parts.moparonlineparts.com

if I look up 56041822AB though everyone lists it as "117A" not "124A"

More Information for REMY 94675

Half the time they're out of what they have on their website.
Looking on Amazon you can get a new AC Delco 117a unit for $109.

 

[RCP Phx]

if I look up 56041822AB though everyone lists it as

My 2k FSM lists it as Denso #56041822AA @ 124 amps!

 

[N8N_99xj]

I guess what I want to know is has anyone bought a "117A" alt for a 2001 and can confirm that it fits/works?

 

[RCP Phx]

I show it (56041685AA @ 117Amps) as std equipment on mine!