Don't post much, most of the answers are here. Dumb enough to keep her going, body work, engine, mechanical. I usually don't sign in, just read. 3 batteries in 4 years. Built in volt gauge usually at 14. When it drops looks around 11 on the gauge, I gave a adapter in the ecu slot, because after replacing the #3 O2 sensor twice, every now and then still sets the code for a weak sensor.. Computer reads about 12.3 volts. It's been fine for a while, acting up again. Replaced the alternator about 3 years ago. Just put another battery in. Did the alternator plug modification for flickering lights..I just wire tied the canister behind the gas door up, https://blazerforum.com/forum/2nd-ge...bracket-92082/ 4 wheel drive didn't engage for crap, redid the vacuum lines about 2 years ago. Tired of replacing caps and rotors every year, when it rained, lost spark. New distributor dumped in. Not fun living in the Midwest, then breaking a spark plug wire... Same with the blower motor, can't crap out in summer, has to wait till the middle of winter... I want to nip this charging issue. When cold, sounds like a vacuum leak passengers side.Warm, not there. I use Torque pro, vacuum -19. Read the threads on this.read in in/hg. Is it a possible bad vapor canister vent valve causing the o2 to trip and voltage to drop. When I had the last alternator tested, it reads good. I replaced it anyways. When it acts up, it's loading down the alternator, like turning the heat or air on. All off that has been replaced, former owner junk yard compressor... Charged it, empty by the end of the day.. Blower motor, resister, compressor, fighting the flickering lights head light switch. The only code it occasionally sets is the O2 sensor.
Tossing around the idea of putting in a 250 amp alternator. I wrenched for 10 plus years, have a good friend who works at the GM dealership, another wrench there has had multiple Blazers. When I lost 4 wheel last winter, took a stab at the 4 wheel module, new and defective, stole it out of one of the junkers in back, worked fine, after they figured out what caused the loss of power to the module... Got 2 new fenders, painted, went to "toss" them on, inner wells were gone. So had to pull the fuse box to replace the inner wells, must have,pulled on a couple wires coming out of it too hard, pulled the spade bits out of the fuse box just enough to lose contact. My 4 wheel module was junk anyways on top of it. Opened it up, found the broken foil runs, soldered jumpers in! Returned the new broken one.... This has been a labor of love. It was my uncles before he passed. Body with the work I've done, is still pretty darn good. Need to figure out the charging issue. If the gauge drops down, normal idle is around 700 rpm, it sill studded a bit, catch and go. Had the hesitation, wasn't from the fuel injection, bad fuel filter. Just tossed another on on. Again, the 250 amp could resolve, but been advised against, where others said should be fine, the alternator should only put out what it needs to keep the battery charged. Anyone run into this? ...

 

Which issue would you like to address first?


George

 

Charging. I'm wondering if it's a vacuum issue it's not causing both.

 

Whats the alternator plug modification for flickering lights?

What is the other problem that you think might be related due to vacuum?

George

 

There was a 2006 service bulletin for all the lights flickering, had to get a new plug, add a ground and ground it to the back of the alternator. I'll see if I still have it and post it. The voltage out of the alternator is rock solid, 13.6 VDC +- a bit. Voltage dummy gauge will drop looks like around 11, ECU still reads 12.3. drops to high 11. It causes a studder in acceleration momentarily. Like I said vacuum is reading almost -20.

 

By the dummy gauge do you mean the dash voltmeter?

Where are you measuring the ECU voltage? Do you mean what a scanner reports?

What is the voltage at the battery terminals through all of this?

I would like to see that TSB

Is the vacuum gauge steady or fluctuating at idle? what is your idle ignition timing? What is your idle rpm?

so at the end of the day a studder during acceleration is the main issue? That can be a lot of things.


George

 

Subject: IPC, Interior Lights and/or Headlamps Flicker - keywords battery courtesy electrical fluctuation generator head intermittent lamp light #PIT3170E - (01/11/2006)



Models: 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.

 

https://www.tsbsearch.com/GMC/02-06-03-008D/250

#02-06-03-008D: Low Voltage Display on IP Gauge,
Lights Dim at Stop Lights, Battery Discharged, No
Start, Slow Cranking, Dim Lights at Ilde, Low
Generator Output - (Jul 21, 2008)
This bulletin is being revised to add the 2009 model year. Please discard Corporate
Bulletin Number 02-06-03-008C (Section 06 -- Engine).
Any vehicle may have a low voltage display (if equipped with gauges), lights that dim at stop
lights, slow cranking, no start, low generator output at idle or dim lights at idle when electrical
loads are heavy at idle or under slow driving or infrequent usage conditions. These
characteristics may be more noticeable with customer added electrical accessories, or with a
discharged battery. These are normal operating characteristics of a vehicle electrical system
and no repairs should be attempted unless a proven fault has been diagnosed.
During normal driving conditions, when engine speed is above 1000 RPM, the generator is
designed to do two things:
The following factors may affect generator and battery performance:
Subject: Low Voltage Display on IP Gauge, Lights Dim at Stop
Lights, Battery Discharged, No Start, Slow Cranking, Dim
Lights at Idle, Low Generator Output
Models: 1990-2009 GM Passenger Cars and Light Duty Trucks
(including Saturn)
2003-2009 HUMMER H2, H3
2005-2009 Saab 9-7X
• Supply the current necessary to operate the vehicle's originally equipped electrical
devices (loads).
• Recharge/maintain the battery's state of charge.
• Non-usage of the vehicle for extended periods of time. The vehicle's computers, clocks
and the like will cause the battery state of charge to drop (For example; 30 days in a
parking lot and the vehicle may not start because of a dead battery or a vehicle which is
driven only a short distance once a week may end up with a discharged battery to the
point where the vehicle may not start). This would be considered abnormal usage of the
vehicle and the normally expected result for the vehicle battery, generator and electrical
systems.
• At idle, vehicle electrical loads may exceed the low speed current (amperage) output of
the generator and when this happens the shortfall comes from the battery. This will result
in a drop in the electrical system voltage as the battery delivers the additional electrical
current to meet the demand. This is equivalent to the brown outs experienced by homes
and businesses when the electrical demand is more than the supply. See Figure 1.
• Extended periods of engine idling, with high electrical loads, may result in a discharged
battery. Attempting to recharge a battery by letting the engine run at idle may not be
beneficial unless all electrical loads are turned "OFF".The following are some typical examples of electrical loads:
Figure 1
Depending on the vehicle application, generator current (amperage) output at engine idle
speeds of 600-700 RPM can be as low as 35 percent of the full rated output. With enough
electrical loads "ON", it is easy to exceed the generator current (amperage) output when the
engine is at an idle of 600-700 RPM. This is a normal condition. The battery supplements for
short periods of time. Items that affect the vehicle's electrical system current and voltage at
idle are the number of electrical loads being used, including add-on accessories, and extended
idle times. When the vehicle speed is above approximately 24 km/h (15 mph), the
engine/generator RPM is high enough and the generator current (amperage) output is sufficient
to supply the current (amperage) requirements of the vehicle as originally equipped and
recharge the battery.
• Increased internal generator temperatures from extended idling can also contribute to
lower electrical system voltage. As the generator's internal temperature rises, the
generator's output capability is reduced due to increased electrical resistance.
System Amperage Load
Rear Window Defogger 25
Electric AIR Pump 25
Heated Seats 5 Amps per seat
Headlamps (high) 20
Blower Motor (High) 20
Headlamps (Low) 15
Brake Lights 6
Windshield Wipers 6
Ignition 6Dimming lights at idle may be considered normal for two reasons:
1. As the engine/generator speed changes, so will the current (amperage) output of the
generator. As a vehicle slows, engine/generator RPM slows and the current (amperage)
output of the generator may not be sufficient to supply the loads, the vehicle system
voltage will drop and the lights will dim. Dimming of the lights is an indication that current
is being pulled from the battery. If the battery is in a low state-of-charge (discharged
condition), the driver will notice a more pronounced dimming than a vehicle with a fully
charged battery.
2. When high current loads (blower, rear defogger, headlamps, cooling fan, heated seats,
power seats, electric "AIR" pump, or power windows) are operating or cycled "ON", the
generator's voltage regulator can delay the rise in output. This effect, usually at lower
engine speeds, can take up to ten seconds to ramp up the generator output. This is done
to avoid loading the engine severely. To increase current (amperage) output, additional
torque is consumed by the generator. The engine computer (ECM/PCM) will ramp up
engine/generator speed in small steps so engine speed variations are not noticeable to
the driver.
For diagnosis of the battery and/or the generator, refer to the appropriate Service Information
(SI) or Corporate Bulletin Number 05-06-03-002C.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the
equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin
applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

 

Just got the one above. Just got this one.