08 WK 3.7 Alternator voltage problem. Plz Help. - JeepForum.com
 
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post #1 of 12 Old 07-17-2021, 09:39 PM Thread Starter
N9Shane
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08 WK 3.7 Alternator voltage problem. Plz Help.

New alternator New battery and under full load voltage drops below 12.75 stalling the jeep, I am not to sure what the problem can be? Any help is appreciated. TIA

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post #2 of 12 Old 07-17-2021, 09:48 PM
Vertisce21
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My first guess is a grounding issue. Might have to spend some time with a voltometer and make sure all the grounds and connections are doing what they should.
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post #3 of 12 Old 07-17-2021, 10:16 PM Thread Starter
N9Shane
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Where can I find a diagram with ground points for this Jeep? Ty.
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post #4 of 12 Old 07-17-2021, 10:49 PM
Vertisce21
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A Haynes manual would likely have that information. You can do a search online and see if you have any luck. I tried and there are a few sites that seem to have the data but they all want money.
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post #5 of 12 Old 07-17-2021, 11:49 PM
Delta0
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Quote:
Originally Posted by N9Shane View Post
New alternator New battery and under full load voltage drops below 12.75 stalling the jeep, I am not to sure what the problem can be? Any help is appreciated. TIA
I had a similar problem.
I took the plug out of the alternator and pushed it back a number of times.
I smeared the entrances to the female contacts with grease before I pushed the plug back for the last time.

Problem solved.

Good connectors as as important as good earths / grounds.

Apart from that, you can get external voltage regulators for WJs, so I expect you can get ext. voltage regs for your motor.

I also ran an extra earth / ground cable from battery post to alternator chassis.
My cable was slightly thicker than the shorter original earth / ground cable.
I would have preferred to use a thicker cable, but 16mm2 was all I had in black.

I now earth the battery with 2 cables instead of just one cable.
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post #6 of 12 Old 07-18-2021, 09:56 PM Thread Starter
N9Shane
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Quote:
Originally Posted by Vertisce21 View Post
A Haynes manual would likely have that information. You can do a search online and see if you have any luck. I tried and there are a few sites that seem to have the data but they all want money.

Unfortunately I ran into the same dilemma. I inspected the most obvious grounds and they seem fine, but I will check them with a voltmeter tomorrow.
Perhaps I may pick up a Chilton or Haynes.
Ty.

Quote:
Originally Posted by Delta0 View Post
I had a similar problem.
I took the plug out of the alternator and pushed it back a number of times.
I smeared the entrances to the female contacts with grease before I pushed the plug back for the last time.

Problem solved.

Good connectors as as important as good earths / grounds.

Apart from that, you can get external voltage regulators for WJs, so I expect you can get ext. voltage regs for your motor.

I also ran an extra earth / ground cable from battery post to alternator chassis.
My cable was slightly thicker than the shorter original earth / ground cable.
I would have preferred to use a thicker cable, but 16mm2 was all I had in black.

I now earth the battery with 2 cables instead of just one cable.

I will take that into consideration and I did see the external voltage regulators topic pop up a few times when I was searching through the forum for similar issues.
I picked up some Dielectric grease and used a bit on the alternator connecter and bulb connectors.
Ty.
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post #7 of 12 Old 07-19-2021, 01:13 PM
90grandoneer
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My guess, ground or PCM, since it's what controls the alternator voltage. A high quality diagnostic scanner should be able to point you in the right direction.

06 GCO, Dk Khaki, QDII, Flshing Hi 3rd Bk Lt, MDS "ON" Lt, Airtab Vortex Gens, Debadged, Fumoto Drain Valve, BT Catch Can, Chopped EGR Tube, SRT8 CAI, AFE Air Filter, 6spd 545RFE, Sonnax Trans Line Press Booster, SC Tuner W/Adv Trans Tune App, DS and HP tuners, Transgo Shift Kit, ARH Long Tube Hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvr, SRT8 frt/rear bumpers, FRI Sidewinder Cam w/6* advance/6.1 valvetrain, SLP 25% UD Pulley, BBK true 90mm T-Body, SOS Ign Coils w/.060 spark plug gaps, TEA ported/milled heads w/new valve seats, SRT Reps with 265/45&295/40X20's. Also 05 Hemi LX modded exactly like WK and, SOLD Comp Cammed 06 300CSRT8 just replaced with 2021 Tesla Model S Plaid with 1020 hp and 1050 lb. ft. of torque.
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post #8 of 12 Old 07-20-2021, 11:14 AM
Delta0
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Quote:
Originally Posted by N9Shane View Post
Unfortunately I ran into the same dilemma. I inspected the most obvious grounds and they seem fine, but I will check them with a voltmeter tomorrow.
Perhaps I may pick up a Chilton or Haynes.
Ty.




I will take that into consideration and I did see the external voltage regulators topic pop up a few times when I was searching through the forum for similar issues.
I picked up some Dielectric grease and used a bit on the alternator connecter and bulb connectors.
Ty.
The ext regs I have seen should give you brighter headlights.
My alternator usually charges at around 13.5v.
An external reg can be set at 14.4v

Dielectric means does not conduct electricity! I'm afraid.
It's not the best idea to use it on contacts I'm afraid.

If you used it on the connectors before you made and broke them a few times,
it's probably best it you clean the grease off with something like brake cleaner, and start again.

Over here in Merry Old England, I can buy something called Pro-contact grease.
I daresay you can buy something similar in USA.

https://uk.rs-online.com/web/p/elect....ds&matchtype=
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post #9 of 12 Old 07-20-2021, 05:10 PM Thread Starter
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Originally Posted by 90grandoneer View Post
My guess, ground or PCM, since it's what controls the alternator voltage. A high quality diagnostic scanner should be able to point you in the right direction.
It may possibly be the PCM gas mileage has inexplicably gotten worse not to mention the stuttering or stalling under full load, another thing to note when auto starting the Jeep under full load the Jeep experiences no issues what so ever until I put the keys in and pump the break then starts to fail?

If it is the PCM I would need one of those high quality scanners to update the programming codes such as installing the vin number to the new PCM from what I have researched.
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post #10 of 12 Old 07-20-2021, 05:56 PM
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Quote:
Originally Posted by N9Shane View Post
It may possibly be the PCM gas mileage has inexplicably gotten worse not to mention the stuttering or stalling under full load, another thing to note when auto starting the Jeep under full load the Jeep experiences no issues what so ever until I put the keys in and pump the break then starts to fail?

If it is the PCM I would need one of those high quality scanners to update the programming codes such as installing the vin number to the new PCM from what I have researched.
This is true. That high quality scanner should also be able to tell you if your PCM is good or bad. On my Autel MS906BT, the PCM is the very first thing it checks when it does an "Autoscan" of all 23 electronic modules. If you have to change PCM's and you pick up a good scanner, you may want to shop around and perhaps get a used one from the same model/year as yours from a junk yard. When I converted the 545RFE in my 5.7 from a 5 speed to a 6 speed, I bought two on line from junk yards, and swapped one into mine and am saving the other one for some "experimenting" at a later date.

06 GCO, Dk Khaki, QDII, Flshing Hi 3rd Bk Lt, MDS "ON" Lt, Airtab Vortex Gens, Debadged, Fumoto Drain Valve, BT Catch Can, Chopped EGR Tube, SRT8 CAI, AFE Air Filter, 6spd 545RFE, Sonnax Trans Line Press Booster, SC Tuner W/Adv Trans Tune App, DS and HP tuners, Transgo Shift Kit, ARH Long Tube Hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvr, SRT8 frt/rear bumpers, FRI Sidewinder Cam w/6* advance/6.1 valvetrain, SLP 25% UD Pulley, BBK true 90mm T-Body, SOS Ign Coils w/.060 spark plug gaps, TEA ported/milled heads w/new valve seats, SRT Reps with 265/45&295/40X20's. Also 05 Hemi LX modded exactly like WK and, SOLD Comp Cammed 06 300CSRT8 just replaced with 2021 Tesla Model S Plaid with 1020 hp and 1050 lb. ft. of torque.
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post #11 of 12 Old 07-24-2021, 10:09 PM Thread Starter
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Originally Posted by Vertisce21 View Post
My first guess is a grounding issue. Might have to spend some time with a voltometer and make sure all the grounds and connections are doing what they should.
After chasing a bunch of wires back to the battery I found a wire on the positive terminal that was kind of loose inside of its terminal.
I am unsure what this wire does exactly, but I cleaned it up nice and give it a new terminal and there seems to be no more charging issues thank goodness.

If it was the PCM I was planning on using a Repair & Return service.
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post #12 of 12 Old 07-26-2021, 10:09 AM
Vertisce21
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Originally Posted by N9Shane View Post
After chasing a bunch of wires back to the battery I found a wire on the positive terminal that was kind of loose inside of its terminal.
I am unsure what this wire does exactly, but I cleaned it up nice and give it a new terminal and there seems to be no more charging issues thank goodness.

If it was the PCM I was planning on using a Repair & Return service.
Sweet! Glad it worked out!
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