Just yesterday I noticed that my headlights in my 2002 trailblazer starting flicking on the way to work. it was the coldest day so far this winter. the battery is less than 2 years old, a gel type ac delco. just changed the serpentine belt and alternator less than 6 months ago. the alternator is a brand new ac delco with a lifetime warranty. going to check the battery connections and the ground first for proper connections. when going to work this morning I watched the voltage meter carefully and it would go from 15 volts to 14 volts. the inside dash would also dim slightly. the headlights do not go out completly,they go from 100% to about 85% . I did have one of my low beam lights go out 2 weeks ago and I replaced it with one that I removed last time another light went out. was going to wait until Spring to change out both low beams again .I do not think that the old bulb could really cause that kind of draw. to me it seems like a possible voltage regulator problem but the voltage regulator seems to be built into the alternator. open to ideas before removing the alternator and taking to back, it was a bear to change. how can I be sure the problem is the alternator? would testing the battery after sitting overnight then with the truck running help me any ? thanks for your thoughts.
headlights flickering
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Id double check all your grounds.
It'd be pretty rare for a new alternator to be faulty, BUT, I'm sure its happened.
I'd re-assess the situation once it warms up as well. Its been BLOODY cold here the last few days. -28 with the wind chill for the past three days. That can do all kinds of funny things.
It'd be pretty rare for a new alternator to be faulty, BUT, I'm sure its happened.
I'd re-assess the situation once it warms up as well. Its been BLOODY cold here the last few days. -28 with the wind chill for the past three days. That can do all kinds of funny things.
My first thoughts were a ground issue. I feel the same that a new ac delco alternator should not be faulty as I have had great durability with them on all of my rides.if it was not such a pain or so cold I would put the old alternator back in. I changed the alternator with the radiator hoses and thermostat this summer. figured while I have the alternator off now would be a good time for a change as it was almost 8 years old. the temp was 17 yesterday and did not really go up. the wind was 20-30 mph most of the day. the battery is strong as it turns the starter with ease. just weird as I have had this truck for a while now and this is the first time I have seen this issue. last winter was brutal here for us and I never had any issue with the battery, so I would be surprised if the battery was at fault.
check the battery cables closely. Might have to cut the rubber bootie off to get a good look at the cables where they bolt to the battery.
Rebuilt alternators from auto parts stores usually have a decent warranty.
But you will probably NEED to use it, as they fail.
Factory or Bosch rebuilds are pretty good.
Remember that power and ground cables have TWO ends, which need to be perfect, and where they connect must be clean and shiny, too.
Cables are easy, and should be checked first - all power and grounds. Look for body grounds and multiple connector grounds under the hood. Lights often use them.
This could obviously be problems from your old worn headlight or a socket.
But you will probably NEED to use it, as they fail.
Factory or Bosch rebuilds are pretty good.
Remember that power and ground cables have TWO ends, which need to be perfect, and where they connect must be clean and shiny, too.
Cables are easy, and should be checked first - all power and grounds. Look for body grounds and multiple connector grounds under the hood. Lights often use them.
This could obviously be problems from your old worn headlight or a socket.
mechtech2,
I will be going over the connections with a fine tooth comb tonight. also decided to just get a new set of headlights and replace the low beams . it does not seem like the old headlight would be the culprit but the issue did start a couple of weeks after putting the old one back in. it only takes a few minutes to change the headlight and I need them anyways so I will try that first.
I will be going over the connections with a fine tooth comb tonight. also decided to just get a new set of headlights and replace the low beams . it does not seem like the old headlight would be the culprit but the issue did start a couple of weeks after putting the old one back in. it only takes a few minutes to change the headlight and I need them anyways so I will try that first.
Hey! There is a Bulletin out for your problem! ID#1619135 - just tell the dealer to look it up. Here is a cut and paste for you:
xTooltipElement
Service Information 2002 Chevrolet TrailBlazer - 4WD | Bravada, Envoy, TrailBlazer (VIN S/T) Service Manual | Document ID: 1619135
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#05-08-42-001: Diagnostic Information on Headlamps Flicker or Momentarily Dim While Driving - (Mar 7, 2005)
Subject: Diagnostic Information on Headlamps Flicker or Momentarily Dim While Driving
Models: 2004-2005 Buick Rainier
2002-2005 Chevrolet TrailBlazer
2002-2005 GMC Envoy
2003-2004 Oldsmobile Bravada
with 4.2L Engine (VIN S -- RPO LL8)
--------------------------------------------------------------------------------
A concern regarding headlamps flicker or become dim while driving may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Below is a guideline to assist with diagnostics.
Verify the customers specific concern.
• What time of day does this occur (is it light or dark outside) ?
• What driving conditions (vehicle speed, engine speed, throttle position, etc...)?
• What was the outside ambient temperature when the condition occurred?
• What accessories was the driver using when this condition occurred (A/C, heated seats, rear defogger, etc...)?
• If the concern is at dusk, could it be the automatic headlamps changing from DRL to Headlamp mode and possibly back to DRL again?
• Are there any other relevant operating conditions?
Diagnostic Information
• Service Bulletin - 02-06-03-008A - Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output (SI Document ID #1540541)
• Service Bulletin - 02-06-03-006B - No Start, No Crank, Battery, Batteries, Generator, Gauge., SES, SIR, Brake, Security, Theft, ABS, Hot, DIC Messages, Lamp, Light, Battery and Generator Diagnostic Testing and Cadillac Roadside Service (SI Document ID #1563904)
• Service Information - Exterior Lighting Systems Description and Operation (SI Document ID #826321)
• Service Information - Battery Inspection/Test (Non-HP2) (SI Document ID #653410)
• Service Information - Charging System Test (SI Document ID #1468059)
• Service Information - Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems (SI Document ID #816776)
Important:
• Keep in mind high current draw items may cause a noticeable dimming of lights and a fluctuation in the voltmeter may be noted and is a normal operating characteristic of the vehicle.
• For 2004-2005 TrailBlazer, Envoy, Rainier and Bravada with the LL8 4.2L engine only, the Secondary Air Injection (AIR) pump activation is thought to be the main contributor to this high current draw condition and is a normal operating characteristic of the vehicle. Refer to Secondary Air Injection System Description (SI Document ID #1298539).
For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats.
Additional high current draw items are rear window defogger, HVAC blower motor, rear air suspension pump along with other components.
For easier diagnostics, it may be possible to control or monitor these components with a scan tool.
It is important to inspect all related connections, grounds and battery terminals for integrity. A loose or corroded connection may exaggerate the concern, and may cause other symptoms. Refer to Testing for Intermittent Conditions and Poor Connections (SI Document ID #1470165).
Corrections/repairs should only be made for specific concerns identified and not related to characteristic of high current draw components.
DO THIS
DON'T DO THIS
Verify the customer concern.
Repairs should ONLY be made if a specific concern is identified.
DO NOT replace the Generator P/N's:
10464468
10464476
unless a specific concern is Identified.
Generators replaced and returned to the Warranty Parts Center (WPC) for review have been tested with No Trouble Found (NTF).
Attempts to repair this condition WITHOUT pinpointing a specific concern may lead to a repeat repair and a dissatisfied customer.
General Motors encourages dealers to share this information with concerned customers.
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.
WE SUPPORT VOLUNTARY
xTooltipElement
Service Information 2002 Chevrolet TrailBlazer - 4WD | Bravada, Envoy, TrailBlazer (VIN S/T) Service Manual | Document ID: 1619135
--------------------------------------------------------------------------------
#05-08-42-001: Diagnostic Information on Headlamps Flicker or Momentarily Dim While Driving - (Mar 7, 2005)
Subject: Diagnostic Information on Headlamps Flicker or Momentarily Dim While Driving
Models: 2004-2005 Buick Rainier
2002-2005 Chevrolet TrailBlazer
2002-2005 GMC Envoy
2003-2004 Oldsmobile Bravada
with 4.2L Engine (VIN S -- RPO LL8)
--------------------------------------------------------------------------------
A concern regarding headlamps flicker or become dim while driving may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Below is a guideline to assist with diagnostics.
Verify the customers specific concern.
• What time of day does this occur (is it light or dark outside) ?
• What driving conditions (vehicle speed, engine speed, throttle position, etc...)?
• What was the outside ambient temperature when the condition occurred?
• What accessories was the driver using when this condition occurred (A/C, heated seats, rear defogger, etc...)?
• If the concern is at dusk, could it be the automatic headlamps changing from DRL to Headlamp mode and possibly back to DRL again?
• Are there any other relevant operating conditions?
Diagnostic Information
• Service Bulletin - 02-06-03-008A - Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output (SI Document ID #1540541)
• Service Bulletin - 02-06-03-006B - No Start, No Crank, Battery, Batteries, Generator, Gauge., SES, SIR, Brake, Security, Theft, ABS, Hot, DIC Messages, Lamp, Light, Battery and Generator Diagnostic Testing and Cadillac Roadside Service (SI Document ID #1563904)
• Service Information - Exterior Lighting Systems Description and Operation (SI Document ID #826321)
• Service Information - Battery Inspection/Test (Non-HP2) (SI Document ID #653410)
• Service Information - Charging System Test (SI Document ID #1468059)
• Service Information - Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems (SI Document ID #816776)
Important:
• Keep in mind high current draw items may cause a noticeable dimming of lights and a fluctuation in the voltmeter may be noted and is a normal operating characteristic of the vehicle.
• For 2004-2005 TrailBlazer, Envoy, Rainier and Bravada with the LL8 4.2L engine only, the Secondary Air Injection (AIR) pump activation is thought to be the main contributor to this high current draw condition and is a normal operating characteristic of the vehicle. Refer to Secondary Air Injection System Description (SI Document ID #1298539).
For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats.
Additional high current draw items are rear window defogger, HVAC blower motor, rear air suspension pump along with other components.
For easier diagnostics, it may be possible to control or monitor these components with a scan tool.
It is important to inspect all related connections, grounds and battery terminals for integrity. A loose or corroded connection may exaggerate the concern, and may cause other symptoms. Refer to Testing for Intermittent Conditions and Poor Connections (SI Document ID #1470165).
Corrections/repairs should only be made for specific concerns identified and not related to characteristic of high current draw components.
DO THIS
DON'T DO THIS
Verify the customer concern.
Repairs should ONLY be made if a specific concern is identified.
DO NOT replace the Generator P/N's:
10464468
10464476
unless a specific concern is Identified.
Generators replaced and returned to the Warranty Parts Center (WPC) for review have been tested with No Trouble Found (NTF).
Attempts to repair this condition WITHOUT pinpointing a specific concern may lead to a repeat repair and a dissatisfied customer.
General Motors encourages dealers to share this information with concerned customers.
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.
WE SUPPORT VOLUNTARY
I like the term, 'fine tooth comb'.
It shows the proper approach.
You will do your car and yourself a great favor in the long run, even if it doesn't fix the immediate problem.
You'll probably have to reset your clock and radio, and it probably will have to be driven a bit to relearn it's idle parameters. So if it acts funny right away after having cables off, don't worry - it's normal.
It shows the proper approach.
You will do your car and yourself a great favor in the long run, even if it doesn't fix the immediate problem.
You'll probably have to reset your clock and radio, and it probably will have to be driven a bit to relearn it's idle parameters. So if it acts funny right away after having cables off, don't worry - it's normal.
I've dealt with flickering headlights several times, and in my experience it's ALWAYS been caused by bad electrical connection- grounds, battery cables, even corrosion where the alternator bolts to the bracket.
That's not to say that a bad alternator CAN'T cause the problem- a bad diode certainly could. But that will usually cause radio noise, too.
That's not to say that a bad alternator CAN'T cause the problem- a bad diode certainly could. But that will usually cause radio noise, too.
Thanks for all of the suggestions so far everybody. GMBoy, thank you for the service bulletin. well here is what happened. I checked the battery leads, both good and tight with no signs of corrosion. checked the ground from the battery to the fender wall, was tight with no corrosion. check the pos and neg terminal ring that goes into the fuse box and they were both tight and very clean. figured the connections would be clean as when I installed the alternator I cleaned all of the connections and put dielectric grease on them. watched the voltmeter and it was still surging like it was. I had bought a new set or low beams on the way home so next I removed the old one and installed the new 9006 bulb. checked the volmeter and it dropped to a hair over 14 .... hmmm maybe we found the issue. have had it out the last two nights and this morning and they remain bright and the voltmeter goes to a touch over 14 and stays there. I inspected the old bulb and it looked fine but it did make it's way to the trash can LOL ! going to keep my fingers crossed that it was that simple.
The contacts will displace the dielectric grease. It's a non-issue.
Well it must have been too good to be true, the headlights started acting up again this morning. best I can figure is the lower temp was needed this morning to make it happen again. the last couple of days it was in the low 30's and today it was 20. back to the drawing board I guess LOL!
Did you try that procedure in the TSB?
"For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats."
Maybe let it idle a minute before driving - just to see.
"For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats."
Maybe let it idle a minute before driving - just to see.
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