Flickering Lights - alternator sense wire

[HenryJ]

Excerpts from ZR2USA thread: Just Installed Big Battery Cables, Now Lights Flicker??

IPC, Interior Lights and/or Headlamps Flicker - keywords battery courtesy electrical flucuation generator head intermittent lamp light #PIT3170E - (Jan 11, 2006)
IPC, Interior Lights and/or Headlamps Flicker
1999-2005 All Cadillac Full Size Utilities

1999-2005 All Chevrolet Full Size Trucks and Utilities

1999-2004 Chevrolet Blazer, S-10

1999-2005 All GMC Full Size Trucks and Utilities

1999-2004 GMC Envoy Classic, Jimmy, Sonoma

1999-2001 Oldsmobile Bravada

Without Regulated Voltage Control

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Customers may have comments of a flickering light condition in the IPC, interior lamps or headlights. This condition is most likely to be noticed when the engine RPM is low and when high electrical load requirements are in place on the generator.

Recommendation/Instructions:
Important: Review bulletin 02-06-03-008A - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, before proceeding with this PI.


Disconnect the negative battery cable from the battery/batteries.
Slide the protective boot on the generator BAT terminal aside and remove the retainer and wire cable from the BAT terminal.
Unplug the generator 4-cavity terminal from the top of the generator.
Inspect cavity D on the generator connector for a red cavity plug. If a red cavity plug is present, it is not necessary to replace the generator connector. Remove the CPA and save. Remove the red cavity plug and continue with step 9. If a red cavity plug is NOT present, continue with the next step.
Remove and save the orange Weatherpack seal and CPA from the 4-way connector.
Using the proper terminal removal tool, remove the two or three wires from the 4-way connector. On vehicles without Supplemental Brake Assist (SBA), install a red cavity plug, P/N 12059168, into cavity "A" of the new 4-way connector, P/N 12186568. On some 2003 and 2004 model year vehicles with SBA, install the dark blue (Circuit 5668) wire of the vehicle wiring harness into cavity "A" of the new 4-way connector.
Depending on the vehicles model and year, install the brown wire (Circuit 25) or red wire (Circuit 225) of the vehicles wiring harness into cavity "B" of the new 4-way connector.
Install the gray (Circuit 23) wire of the vehicle wiring harness into cavity "C" of the new 4-way connector.
Obtain a piece of 0.80 mm/18GA black wire, 254 mm (8 in) long.
Install a red terminal seal, P/N 12048086, and terminal, P/N 12048074, (crimp and solder) on one end of the new black wire.
Install the new black wire into cavity "D" of the new 4-way connector.
Reinstall the connector seal and CPA, from the original connector, to the new connector.
Plug the 4-way connector into the generator.
Route the black wire to the generator BAT terminal, sliding the wire into the small end to the output terminal boot, along side the generator output wire.
Obtain a ring terminal from the terminal kit (J-38125-D) that is the same diameter as the positive post of the generator. Crimp and solder the ring terminal from the terminal kit (J-38125-D) on to the open end of the new black wire.
Place the generator output wire and the new black wire onto the generator BAT terminal and install the retainer.
Connect the negative battery cable.
Note: This modification will not work if the vehicle is utilizing the new "Regulated Voltage Control" system. This is new feature on some full-size trucks and utilities for the 2005 model year. Please inspect the vehicle prior to performing this modification.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Ok, I've done some more research, and here is what I've found:

GM Part # 15306009

That's the complete plug with a pigtail. It comes loaded with 4 wires coming out of it.

That should work for me, however, the only dealership that has it in stock, want's $44.48 for it..

GM Parts Direct has it for $20, but you have to wait on shipping.

Just to test out this theory, I just took a piece of 18g wire, and stripped an inch of it back, and "inserted" into the S pin hole in the terminal. That way, when I pushed the connector it, it held the wire tightly onto the corresponding terminal. (Redneck engineering at it's finest)

I then ran the other end of the wire to the alternator output stud.

That seems to have fixed my problem! I started it up, checked output, and then turned on all of my lights. I couldn't see anything flickering, and was very pleased.

I just got done calling all of the local parts stores, and NAPA came to the rescue.

They have it in stock, for $23. Now that I know that it fixes my problem, I have no problem paying that!
Just for future reference, the connector can be looked up by:

AC DELCO Part # PT1136

That's the full connector assembly with a pigtail of all 4 wires coming out of it.

[04crewvt]

So is this a repair that will not be covered under a special service policy? I just noticed my dash lights start flickering last week and just thought I hadn't noticed it before.

[HenryJ]

No policy that I know about. All you need to do is add the remote sense wire. You can pick up a terminal at a rebuilder and add it to your connector, or get one in the salvage yard.

[green02crew]

Is there a way to get pictures of said process? My lights flicker at idle I had always assumed it was normal!

[HenryJ]

Is there a way to get pictures of said process?

My lights have not flickered, but I am a glutton for punishment, so lets walk through the "no budget method"

Follow all safety procedures for working on a vehicle and electrical system. Disconnect the battery prior to the work. Ignore the blue spade terminals you see in these pictures. My truck has been a test bed for quite a few alternators and those are a quick method for attaching different regulators.

The regulator is marked, however it is facing the rear of the vehicle and hard to see. It's connections are as follows:
P L I/F S
P..Stator
L..Light
I/F..Ignition/FR
S..Sense
You can use a mirror to see these markings:



The "S" terminal is the one we want to attach to the positive stud on the back of the alternator.

You can get a connector at the salvage yard for little or no cost. I keep a few around for times like this:



Pop the black plastic retainer off and use a pick to fold the retention prong down so you can slide the terminal out the back side. You can see that prong in the next picture:



This is the wire you need to assemble (pictured above) Solder and heat shrink the eye terminal to attach to the battery stud on the back of the alternator.

The connector on your alternator will have the hole you need to insert this wire "blanked". It will be blocked like the second one in this picture:



Use a drill to just clear the blank. Do not drill all the way through the connector! You need the squared portion to orient the terminal. Once drilled it will look like the hole on the left in the above picture.
Once ready, insert the terminal from the back side you may have to square it a little with some pliers to get it to fit and a small screw driver to push it into place. It will not have the groove to keep it from pushing too far, nor the slot for the retention prong to keep it from pulling back.

Once in place and seated forward like the rest it will look like this:



Snap the black plastic retainer back on and plug it back into the regulator.

You will need to remove the cable from the battery stud on the back of the alternator and slide the wire from the alternator in that black rubber boot. stack it on your other wire and bolt them back up.



For those who bought the four wire pigtail connector mentioned , all you need to do is cut the wires and then solder and heat shrink the connections, or you can swap terminals and save cutting the wires. These pictures should help with where and what a little.

[green02crew]

Wow thats quite the walkthrough! Thanks! Looks like I'll have a project for next weekend.

Is there a reason that our vehicles came without this connection? Is it bad that the system has fluctuating power causing the lights to flicker like this?

[HenryJ]

The regulator senses the voltage internally. There is really no need for the use of the remote sense wire.
It is designed to be run to the electrical center. Voltage for the system would then be based on the voltage at that point instead of at the alternator.

Is the fluctuation bad? I don't see it as good.

Why does this work? I really don't know. I can guess that some regulators may exhibit a condition in which the internal sensing of voltage tends to fluctuate. This condition is cured by sensing remotely.

They say it works. That is enough for me. Try it and let us know if yours if cured.

[green02crew]

Ok so just to verify, the sense wire just routes to the back of the alternator into the stack of wires there? It just seems too simple.

[HenryJ]

To the positive post, yes. Let us know if it works for you.

EDIT to add key words instrument cluster, odometer, speedometer, flickering, dash, lights.

[green02crew]

Ok so I managed to get it done today, took all of about 10 min tops for this project. It really does work, there is no more flickering at an idle. I still don't fully understand how it works but I'm happy.

On another note, what voltage should it be at when running, minimum? I ran all my accessories, a/c, lights ect. and could pull the voltage down to about 12.2 is this bad? That isn't normal use. Normally it runs about 13.5 or so.

[HenryJ]

what voltage should it be at when running, minimum? I ran all my accessories, a/c, lights ect. and could pull the voltage down to about 12.2 is this bad? That isn't normal use. Normally it runs about 13.5 or so.

Voltmeter Reading State of Charge

12.84 Volts or higher 100%
12.50 Volts 75%
12.18 Volts 50%
11.88 Volts 25%

You are on the low side and losing. You really need to be closer to 14 volts to maintain the system.
try a smaller pulley, or a bigger alternator.

remember that the stock 100 amp alternator is fine to maintain the stock system. If you add loads you need to compensate.

[green02crew]

Ok so I should aim to keep it in the 13+ range. This was all done at a hot idle, when moving I can run everything and there is no issue. AD244 may have to be on its way...

[HenryJ]

If it picks up with a few rpm, add a 2 mm smaller pulley and you will be fine.

[BDiefAZ]

2 questions:

Does the smaller pulley require a different belt or will the tensioner compensate?

Would this mod work on a 1998?

[HenryJ]

The smaller pulley may require a shorter belt.
The tensioner has a pretty limited range for function. Watch the lower hose. With a belt too long you can get really close and even rub the lower radiator hose.

This should work for a '98 , as far as I know there are no differences.

[raven2510]

just did this on my zr2 and i solved my problem
i just wanted to say thanks

[HenryJ]

Found some long lost photos and updated the thread

[Jongo88]

I had to do this on my Crew...