External voltage regulator or not

[Logan Savage]

2005 Liberty 3.7 . With field wires plugged into alternator I get a code for # 4 injector & engine won't rev above 2200 rpm's .
Unplug field wires , clear codes & engine runs fine . Have tried two alternators & batteries & new PCM .
I read to test the alternator to see if it's charging to unplug the field wires & jumper the field terminals on the alternator , one to battery terminal on alternator & other wire to alternator case . When I tried this the injector code & no rev problem came back .
Seems like I have an overcharge problem instead of an undercharge problem or it's something else entirely . I am considering adding an external regulator kit . Any ideas on these problems ?

 

[renegade 04]

Have you tried replacing the battery temperature sensor? If not I would try that because the input from the battery temperature sensor affects the charging voltage.

 

[Logan Savage]

I don't think the 05 has the battery temperature sensor , correct me if I'm wrong .

I just checked rockauto & they list one for an 04 but not for an 05 .

 

[renegade 04]

I have a external voltage regulator, But I think your problem may be a bad alternator or battery than once you have ruled those out then you could think about installing one.

 

[Billwill]

The 05 upward models do not have the battery temp sensor installed.
This sensor only has a slight effect on the charging rate in any case.

I replied to this post on the Jeepforum site....bear in mind that if you place +12 volts on the field coil it will drive the output voltage up to about 17 volts at which time the PCM will detect on over-voltage and should power everything down...the field coil relies on a PWM pulse from the PCM to vary the output voltage up or down. If this is not happening then maybe the PCM is not measuring the alternator output as it is supposed to do. I had this overvoltage problem on my 2002 Export CRD...caused by several wires shorting to each other in the harness...switch on aircon or front wipers and voltage rises to +17 volts and engine shuts down!

 

[Logan Savage]

Billwill , I saw & replied to your post on the other forum . I checked battery voltage with engine off on the battery posts & got 12.76 volts . With all wires connected & the engine idling I got 14.33 volts on the battery posts .
Since the engine doesn't cut out till about 2200 rpm's , perhaps I should have watched charging voltage on the battery posts while increasing rpm's from idle . Maybe the faster the alternator spins the higher the charging voltage gets until it gets too high .
As I said before , I've tried 2 alternators & 2 batteries & new pcm .

 

[renegade 04]

Here is a link to how I wired mine in. currently I am running a vary old school ford mechanical voltage regulator.
http://www.jeepkj.com/forum/f196/battery-light-keeps-coming-again-58511/index2.html

 

[JasonJ]

Billwill , I saw & replied to your post on the other forum . I checked battery voltage with engine off on the battery posts & got 12.76 volts . With all wires connected & the engine idling I got 14.33 volts on the battery posts .
Since the engine doesn't cut out till about 2200 rpm's , perhaps I should have watched charging voltage on the battery posts while increasing rpm's from idle . Maybe the faster the alternator spins the higher the charging voltage gets until it gets too high .
As I said before , I've tried 2 alternators & 2 batteries & new pcm .

Hmm, very curious. I have seen where an alternator that tests good, is actually not at higher rpm. What was happening was that at higher rotational speeds, the brushes were making contact with the stator and internally shorting the alternator.

But you say you've tried 2 new alts and 2 batteries... not sure I can help. It definitely sounds like a voltage regulation or other electrical control issue.

 

[Billwill]

Billwill , I saw & replied to your post on the other forum . I checked battery voltage with engine off on the battery posts & got 12.76 volts . With all wires connected & the engine idling I got 14.33 volts on the battery posts .
Since the engine doesn't cut out till about 2200 rpm's , perhaps I should have watched charging voltage on the battery posts while increasing rpm's from idle . Maybe the faster the alternator spins the higher the charging voltage gets until it gets too high .
As I said before , I've tried 2 alternators & 2 batteries & new pcm .

Yes I think test the voltage across the battery at 2200 rpm....should not increase much above your 14.33..:shrug: