Overcharge of battery cutting out instrument cluster

[Kaden5645]

Hi, I recently had a alternator go out on me. I replaced the alternator. When the key is in the accessory mode the cluster and everything works. Battery is at 12.7 volts. As soon as I fire the jeep up the battery voltage goes up to 19volts and the cluster completely goes out. I checked all the grounds and wires. Cleaned everything. Could it be that the PCM is telling the alternator to overcharge do to the battery having bad cells in it and from the power surge cutting out the instrument cluster? I'm at a loss right now. Any feedback would be much appreciated! Thanks you

 

[LibertyTC]

If you suspect any issue with the battery replace it or try another known good battery. The KJ does wonky things with a bad battery.
You should not be viewing a 19 volt output, what brand/model of Alt did you buy?
See also Gen Discussion thread about topic. https://www.jeepkj.com/threads/help-instrument-cluster-high-beams-not-working.73092/

 

[Kaden5645]

So in your opinion do you think the battery or alternator could be shot not the PCM. By the way the alternator is a remanufactured one.

 

[LibertyTC]

It is a matter of elimination. Can you get the battery load tested?
Code P0622 Generator Field Not Switching Properly, that may very well point to the re-manned Alt.
Hopefully Bill our electrical specialist chimes in, as he will offer further related testing.

 

[Kaden5645]

Yeah I'm gonna get the battery and the alternator load tested tommorow. We will see what happens. Thanks

 

[Billwill]

Ouch! Most of my many problems that I had with my damaged wiring was caused by a wire in a harness somewhere shorting to chassis or to some other random wire.
With multimeter plugged into the front power outlet I could monitor the voltage while driving.
Voltage would sit at a nice 13.5 while driving....I turn the air-con or the front wiper ON and the voltage rapidly rises to 17 volts and engine dies!

What year/model do you have?

What problem did you have previously that caused you to replace the alternator.....I do not trust the re-build I think!

 

[Kaden5645]

Well a few nights ago i fired my jeep up. It's a 2003 jeep liberty limited. Everything was good then I hopped in and gotta dummy light for the battery. Drove it home anyways cus I had to. The dash lights and headlights were very Dim. Jeep had almost no power to. Then I pulled into my driveway and the cluster and everything went black. I shut it down and then tried to fire it back up but the battery was completely drained. Took the altenator in and had it load tested. It surprisingly came back good but the bearings were shot in it. Baught a remanufactured one anyways. Put it in yesterday. While the key was in accessory mode everything was fine. Dash lights were good. All the gauges worked. As soon as I started the jeep the cluster would stumble for a minute then cut off. One of my headlights got burnt out in the process and now I dont have highbeams or the cluster. When the car is running the battery voltage spikes up to over 19volts signaling a overcharging issue. Three codes popped up as well P1594,P0622, and P1687.

 

[Billwill]

OK the P0622 code is, as stated, The Generator Field Control Circuit.

Now it would seem that your original problem was that the battery was not charging at all hence the lights going dim and then not starting.

My big concern is that your replacement alternator may be faulty or may be the wrong PN for your 2003 Jeep. The 2003 Jeep Alternator has a field coil built inside it...this is the small 2 pin connector on the alternator. One pin, pin #2, goes to +12 volts on the PCM, the White/Dark Blue wire....check that +12 volts is there! The pin #1 Dark Green wire also goes to the PCM.
The PCM reads the voltage of the battery and adjusts the current output by putting negative pulses of varying length on pin#1. This is called Pulse Width Modulation (PWM). The longer this negative pulse is the greater the voltage put out by the alternator.
So if pin #1 Dark Green wire is shorted to engine/chassis it means the alternator will put out maximum power which is what you are getting. So you need to disconnect the battery and pull plug # C2 off the PCM and pull the small plug off the alternator.
So this Dark Green wire should be hanging in mid air...test with a Muti-Meter that it is not in fact shorting to chassis which would cause the generator output to go to maximum.

Different year KJs use different methods to adjust the generator output voltage which is why you must have the correct Part Number! I will check into this but maybe you should replace the bearings in your original alternator and use it.

You can download the 2003 Jeep KJ Service Manual here.
Section 8F describes how the alternator works and Section 8W has the wiring diagrams...your main interest is page 8w-20-2.

These wiring problems can be difficult to find! You may have blown some fuses with the higher voltage!

www.colorado4wheel.com/manuals/Jeep/KJ/

OK the 2006 Jeep KJ 3.7 gasser wiring diagram shows the same type of charging theory to the 2003 wiring diagram but pins 1 and 2 are the other way around. This is not unusual for the wiring diagrams to have errors. So maybe pin#2 the White/Dark blue wire is the one that gets switched to ground and this wire is the one that needs to be checked for a short to ground!

 

[Kaden5645]

Alright well. I went and got my alternator and battery tested. The battery was perfectly fine but the new remanufactured altenator was completely junk. Failed immidedently after turning the machine on. I forgot to mention I baught it at AutoZone. The guy there tried to tell me the PCM voltage regulator fried the alternator. Not to sure on that. Think I just baught Autozone crap. Thing of it is it's the only auto parts store around me. Guess we will see come tomorrow when I pick another one up‍

 

[ltd02]

Have them test the new one before you leave the store. I've heard of many people who do this with alternators.

 

[lfhoward]

There’s also the used Mopar option. I tend to think sometimes this is a better bet than aftermarket.

www.car-part.com

 

[Kaden5645]

Thanks, I will tommorow. I'll keep you guys updated on if another alternator fixes my issues.

 

[Billwill]

Check all your fuses while you are waiting as the high voltage may have blown something.

P1594 Charging system too high
P0622 Alternator field circuit
P1687 No Cluster Bus Message

Hopefully all the above will work once new alternator is in place otherwise we will deal with them one at a time!

 

[Kaden5645]

Well guys I got it fixed. It was the altenator. Had the guy bench test this one out of the box and it was good. He was trying to get me to buy a New pcm. I put it in and bam everything works now but the headlights. I must of blew them with the crap alternator. Never going to AutoZone ever again! Thank you guys for helping and giving me feedback✌

 

[LibertyTC]

Good to hear another alt worked.
If and when my alternator fries, I would only consider a Denso, Ac Delco or Bosch.
They seem to have better quality controls than many of the others.
Also for new, Quality Power in California can offer great basic or custom products.

 

[Billwill]

Well guys I got it fixed. It was the altenator. Had the guy bench test this one out of the box and it was good. He was trying to get me to buy a New pcm. I put it in and bam everything works now but the headlights. I must of blew them with the crap alternator. Never going to AutoZone ever again! Thank you guys for helping and giving me feedback✌

If the headlight bulbs themselves are blown then the fix is obvious.
If not then the high beam relay is the small relay on the front of the interior fuse panel....lots of identical relays such as low beam relay are behind the fuse panel to swap over!

Otherwise check which fuses are involved and climb into the wiring diagrams.

The PCM/ECMs are pretty tough...Dealers always want to replace them first whereas I always want to replace them last!

 

[Kaden5645]

Yeah all that blew was the bulbs themselves and the blower moter resistor for the heater thankfully.

 

[David Ruozi]

I'm going through the exact same issue with my 2008 KK. This post was very helpful especially BillWill and his explanation of charging system and PCM.

My alternator fried to the point of smoking while my wife was driving. I get a new alternator, put it in and next thing the jeep is possessed, every light on dash pops on, all the lights cut out and back on over and over. I pull over shut it down and have been chasing shorts for 3 days. Alternator won't charge batt and I've been worried the PCM was shorting out and frying both my alternators.

 

[Billwill]

Just a quick thing to look for:
The thick wire on the alternator going to the + side of the battery has a "fuse" built into it.
This is called a Fusable Link and its purpose is to blow if there is a direct short on this thick lead to chassis....carries lots of current!

If you put your voltmeter on the positive post of the battery and measure to chassis you expect to see +12 volts. Likewise the large stud on the alternator should show +12 volts unless the Fusable Link has blown.

You can remove this Link and measure the continuity of this link...if blown then you need a new Link of the correct rating.

Also whenever you work with this Link or the Alternator always disconnect the Negative Lead on the Battery first or your wrench on the large lug touching ground will blow the Link.

If none of the above is your problem I will get back to you..just make sure you have the correct alternator for your model Jeep!

What year/model is your Jeep?