Voltage Drop at WOT - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 16 Old 12-27-2016, 07:06 PM Thread Starter
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Voltage Drop at WOT

Guys I need some help. I am getting a full voltage drop at wide open throttle. Here's my setup.

2007 JK unlimited
Ripp supercharger
Upgraded alternator, starter, and TIPM cables (2 gauge)
Upgraded ground cables (4ga right now, but I am in the process of changing them to 2 gauge)
New Alternator (that tests OK at the auto parts store, replaced this year)
Optima Yellow Top Battery
Distribution block and auxilary fuse box

What I've tried so far:
Replaced alternator (tested bad)
Replaced serpentine belt
Replaced belt tensioner
Replaced 4 gauge power wire with 2 gauge (thought there might be a short, there wasn't)
The starter wire has a fiberglass heat sleeve on it

I have an android based head unit with TORQUE installed and a bluetooth ODBII unit that communicates with it. So I can graph my voltage as I drive. When I give it heavy acceleration, the voltage drops from 14.4 v (alternator) down to 12v (battery power). I am getting Terminal field generator faults (sometimes) and sometimes random misfires (although that could be due to something else, like the RIPP long tube headers sucking air). I'm going to try to disconnect the auxillary power system and see if there is something there causing it, however all of that is fused. There is a large fuse on the 2/0 cable running to the distribution block, then two large fuses (160 amp and 200 amp I think) in there. Then the secondary fuse box has all 30 amp fuses. So any short beyond that which would be severe enough to pull all my voltage down would pop a fuse. The auxiliary fuse box is literally 3 or 4 inches from the distribution block. so no chance of short there. I've added an extra 4 gauge ground cable from the battery to the alternator bracket to ensure it isn't a block ground issue.

I don't think it is a belt slipping and I've not changed the alternator pulley. I realize that overspinning the alternator can cause this type of effect.

So all I'm left with is maybe a bad TIPM module. I think I read somewhere that the TIPM has the voltage regulator in it, not the alternator like the older alternators. Is that accurate? If so, how do I test that? I hate to replace a $500 + TIPM on a "might be" basis.

Tomorrow I will try disconnecting the winch cable and auxiliary fuse block system. That would leave only the starter, TIPM, and Alternator connected to the battery. If I still get drop what else can I check???

Thanks,
Rescu2000
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post #2 of 16 Old 12-27-2016, 07:18 PM
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The voltage regulator is in the PCM.

What is the engine rpm during the low voltage wot?

What codes are you getting when this happens?

Ask RIPP if their program sheds the alternator when max power is requested.

2008 Unlimited Rubicon Automatic

Last edited by ronjenx; 12-27-2016 at 07:31 PM.
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post #3 of 16 Old 12-28-2016, 06:38 AM
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what was added prior to or when was the first time you noticed this drop ? Many variables but I wondered when it began and what fault codes it's throwing ?


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post #4 of 16 Old 12-28-2016, 09:01 AM
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I'm an analog guy so take this fwiw...

What are the chances that everything's good?

If the electrical systems take their juice from the alternator/rectifier/regulator before the juice gets sent to the battery, I'd say it's a very good chance.
With any extra initial draw on the system when asking for WOT, the alternator may not be able to immediately supply all of the necessary juice "on demand". So now the "brains" call on the battery to boost the supply of juice. That could be your voltage drop.
And/or, this delay upon WOT could be a symptom of our nanny-state computers taking time to process the signals...like hitting the horn, and how long of a delay is that? That should be relatively instantaneous. Or, when ESP or TC kicks in, it doesn't shut off until/unless you back off...wtf, right?

Maybe do a momentary backing off of WOT, then get right back into it and see what your graph tells you?

You may not have an issue at all. At least, not a function issue...but certainly, imo, there are issues with the design.

Last edited by funfred; 12-28-2016 at 09:23 AM.
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post #5 of 16 Old 12-28-2016, 10:09 AM Thread Starter
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The exact fault I get is p0622 generator field "f" terminal control circuit. I disconnected the auxillary fuse block and winch and still get the drop. It stays low for as long as I hold WOT and then returns to normal when I let off. I'll try letting off and then going back to wot to see what happens.

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post #6 of 16 Old 12-28-2016, 10:15 AM
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Below is the list of normal possible causes.

Give Ripp a call and ask what they think, and if their program sheds the alternator when max power is requested.

Possible Causes

GEN FIELD CONTROL CIRCUIT SHORTED TO VOLTAGE

GEN FIELD CONTROL CIRCUIT OPEN

GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND

GENERATOR

POWERTRAIN CONTROL MODULE (PCM)

2008 Unlimited Rubicon Automatic
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post #7 of 16 Old 12-28-2016, 10:16 AM Thread Starter
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Also, it isn't in the ripp program, because I've had the supercharger for several years and the problem started a few months ago. I don't think I added anything at the same time, but it is possible that I added the long tube headers about then. I thought it was a slipping belt at first so I didn't think much about it and just replaced the belt and tensioner. That didn't help.

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post #8 of 16 Old 12-28-2016, 10:29 AM Thread Starter
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I'm going to check the field control wire from the pcm this afternoon. If that isn't loose or shorted, I'm afraid it is going to be a bad pcm...

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post #9 of 16 Old 12-28-2016, 06:53 PM Thread Starter
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I wiggled all of the harness wires, connections, PCM connections, etc and couldn't get the voltage to drop. The connections weren't lose and didn't cause a drop. It's really looking like the most expensive part, the PCM. I'll pull it out this weekend and check it for bad solder joints and connections. I'll report back what I find.

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post #10 of 16 Old 12-28-2016, 06:54 PM Thread Starter
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Quote:
Originally Posted by Rescu2000 View Post
I wiggled all of the harness wires, connections, PCM connections, etc and couldn't get the voltage to drop. The connections weren't lose and didn't cause a drop. It's really looking like the most expensive part, the PCM. I'll pull it out this weekend and check it for bad solder joints and connections. I'll report back what I find.

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Here is what happens when I give it full throttle, let off and then go full throttle again...
Quote:
Originally Posted by Rescu2000 View Post
I'm going to check the field control wire from the pcm this afternoon. If that isn't loose or shorted, I'm afraid it is going to be a bad pcm...

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post #11 of 16 Old 12-28-2016, 06:57 PM Thread Starter
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Another thing occurred to me to help eliminate possible suspects. I'll bypass the supercharger and put a standard belt back on it.

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post #12 of 16 Old 12-29-2016, 07:02 AM
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sounds so much like improper ground somewhere in the "chain" but I also wonder about PCM ultimately. The belt bypass of SC isn't a bad idea just to eliminate that poss


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post #13 of 16 Old 12-29-2016, 07:35 AM Thread Starter
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I have the cabling and parts to replace all of the major ground cables with 2 gauge welding cable. I'll do that this weekend too.

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post #14 of 16 Old 12-31-2016, 07:28 PM Thread Starter
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I Added another ground cable to the chassis. No joy. Also pulled the TIPM out and checked connections there. Still haven't traced the field control wire or replaced all of the ground cables. I've been sick and it has been cold and rainy here. So I don't think I'll get much done this weekend.

On the trip to test t out, it is falling out at 4k rpm. I'll test that some more tomorrow.

As for the question on what has been added, that list is so long it isn't going to help, but here is a stab at it. In the past 6 months:
Synergy Track Bar Brace, track bar, and sector shaft brace
Red LED underside rock lights
LED headlights and fog lights
White LED underside rock lights
22" LED Light bar
50" LED light bar
2nd fuse box, wiring, and all switches for the accessories
Heated leather Katzin seats
Tuffy glovebox, security console, read deck enclosure
Rockford fosgate speakers front and roll bar
Kicker seperates in speaker pods on the rear roll bar
Android aftermarket head unit
Rockford fosgate marine amplifiers
Axle sleeves and truss for front axle (no effect, just being thorough)
Gauges for air temperature before and after intercooler, air pressure, boost
ARB air compressor
sealed custom airbox for snorkel
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post #15 of 16 Old 01-06-2017, 02:47 AM
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I've been doing a lot of searching and the PCM sends signals through the TIPM to control the alternator charging. Even dealer technicians don't have a good way to troubleshoot these problems without finding grounding issues or a bad alternator. The solution in every instance I've seen is new PCM, new TIPM, and new harness. Most likely somewhere in your grounding upgrades something was missed. When that happens ground go through alternate paths never intended to carry the current and burn open or create high resistances.

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post #16 of 16 Old 01-14-2017, 11:24 PM Thread Starter
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Thanks for the info. I've pretty much reached the conclusion it is in that system as well. I can't find any bad wires and it charges fine most of the time. Since it is intermittent I may just leave it alone until it fails completely. I plan on doing an LS or Hemi swap at some point anyway.

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