Here's a quick question. For some time I notice that when my car idles the lights inside and outside fluctuate, dimming and undimming probably three times a second. It's heard in the engine too. I changed the alternator about a year ago because it was charging low. The fluctuating dimming happened before nad after the alternator change. Is this a problem? Thanks!
fluctuating lights
- Thread starter dlnelsonroca
- Start date
Chickenhawk
Member
- Dec 6, 2011
- 779
If you get dimming while driving, especially when backing off the gas, it is irritating, but common. Some of us have been chasing this for years. New alternators or new batteries solve the problem for a few months and then it comes back again. Many of us have checked cables and grounds and some - like myself - have even added auxiliary battery cables. (The "big three" mod.) No solution yet. It just seems to be part of our platform.
It almost seems it's part of the PCM, and if the battery is brand new or the alternator is brand new, it stops for a while but then comes back. Check your cable connections and grounds, get the alternator checked out and load test the battery. Also follow the suggestions from other members of this forum, but if everything checks out okay, there might not be a solution.
It almost seems it's part of the PCM, and if the battery is brand new or the alternator is brand new, it stops for a while but then comes back. Check your cable connections and grounds, get the alternator checked out and load test the battery. Also follow the suggestions from other members of this forum, but if everything checks out okay, there might not be a solution.
There is another possible "Draw-Down for The Juice" that can occur just after starting the TB and then several times afterwards that might scavenge enough energy to dim the head lights: The SAIS Pump.
When the vehicle is first started ...the SAIS Pump starts running... and is trying to push enough air through the Catalytic Converter in order to raise its temperature as soon as possible. This action ensures that better High Temp Chemistry within the ceramic honeycombs covered in Rare Earth Metals can happen and this allows the CAT to work more efficiently.
So if it is especially cold out or just after you start the vehicle... for about 7-10 seconds or so... that motor under there is eating up as much 12VDC as necessary ...while whirring away to do this job. If this occurs... the energy normally "Heading for The Headlights" is getting scavenged ...and so the lights might dim as a result.
The same actions may happen again... a minute or two after you head off down the road and should the SAIS Pump really misbehave and leave itself running constantly... it will draw the 12VDC energy even longer until the cause of the problem eventually gets discovered as a BAD SAIS Solenoid Valve located on the center-passenger side of the engine head.
EDIT:
I was just thinking that this theory would be easy enough to test out as a single variable... by simply starting the vehicle while parked and at idle with the headlights on... and command the SAIS Motor to run. If the lights dim under those conditions... then that event would indicate that the SAIS Motor does indeed draw enough 12VDC to make the headlights go dim when it is running. :>)
When the vehicle is first started ...the SAIS Pump starts running... and is trying to push enough air through the Catalytic Converter in order to raise its temperature as soon as possible. This action ensures that better High Temp Chemistry within the ceramic honeycombs covered in Rare Earth Metals can happen and this allows the CAT to work more efficiently.
So if it is especially cold out or just after you start the vehicle... for about 7-10 seconds or so... that motor under there is eating up as much 12VDC as necessary ...while whirring away to do this job. If this occurs... the energy normally "Heading for The Headlights" is getting scavenged ...and so the lights might dim as a result.
The same actions may happen again... a minute or two after you head off down the road and should the SAIS Pump really misbehave and leave itself running constantly... it will draw the 12VDC energy even longer until the cause of the problem eventually gets discovered as a BAD SAIS Solenoid Valve located on the center-passenger side of the engine head.
EDIT:
I was just thinking that this theory would be easy enough to test out as a single variable... by simply starting the vehicle while parked and at idle with the headlights on... and command the SAIS Motor to run. If the lights dim under those conditions... then that event would indicate that the SAIS Motor does indeed draw enough 12VDC to make the headlights go dim when it is running. :>)
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jsheahawk
Member
I recently have had a surge from time to time, that's with LED headlights and no SAIS pump @jsheahawk @MRRSM. IMO, I really just think it's something that varies as to the cause, on a case-to-case basis.
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jsheahawk
Member
These are the tools for the investigation of a Parasitic Draw on the Electrical System… with a link to an exhaustive “How-To” from All-Data… but I am not sure if this thing would apply or work for checking out components in the system ...with the engine running:
https://www.amazon.com/s/?ie=UTF8&k...qmt=p&hvbmt=bp&hvdev=c&ref=pd_sl_4ch3xyje3h_p
This PDF gives some Guidance on how the Parasitic Drain Tests are conducted:
http://flashoffroad.com/electrical/CurrentDrain/currentdrain.pdf
...and at about 2/3rds of the way down the page comes the GM All-Data Information….
https://community.cartalk.com/t/what-is-normal-parasitic-current-drain/20444
Also... I think @Capote is right... and while I would still very much like to know what the "parasitic drain" the SAIS Pump might cause on the power balance in the vehicle... Here is another possible place to look for the cause:
Bulletin No.: 02-01-39-007B
Date: November 05, 2007
INFORMATION
Subject:
Automatic Dual Zone HVAC Battery Draw
Models:
2004-2007 Buick Rainier
2003-2008 Cadillac Escalade Models
2002-2008 Chevrolet TrailBlazer
2003-2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2002-2008 GMC Envoy Models
2003-2008 GMC Sierra, Yukon Models
2002-2004 Oldsmobile Bravada
2003-2008 HUMMER H2, H3
2005-2008 Saab 9-7X
Supercede:
This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 02-01-39-007A (Section 01 - HVAC).
When diagnosing battery draws on trucks equipped with the automatic dual zone HVAC controls (RPO CJ2), technicians should keep in mind that the control head does not completely "go to sleep" until after 150-250 minutes, or up to 4-1/4 hours, from when the ignition key is turned OFF. This is a normal condition. In these cases, DO NOT replace the control head.
...and perhaps one more....
A while back.... @Mooseman was explaining the A/C Portion of the HVAC system in the full sized SUVs to a Member once and he mentioned that there is a second "Mini-AC System" with its own compressor/condenser/evaporator unit in place to cool the passengers in the back of the vehicles... perhaps that unit is rapidly cycling on and off and causing the power drain...?
https://www.amazon.com/s/?ie=UTF8&k...qmt=p&hvbmt=bp&hvdev=c&ref=pd_sl_4ch3xyje3h_p
This PDF gives some Guidance on how the Parasitic Drain Tests are conducted:
http://flashoffroad.com/electrical/CurrentDrain/currentdrain.pdf
...and at about 2/3rds of the way down the page comes the GM All-Data Information….
https://community.cartalk.com/t/what-is-normal-parasitic-current-drain/20444
Also... I think @Capote is right... and while I would still very much like to know what the "parasitic drain" the SAIS Pump might cause on the power balance in the vehicle... Here is another possible place to look for the cause:
Bulletin No.: 02-01-39-007B
Date: November 05, 2007
INFORMATION
Subject:
Automatic Dual Zone HVAC Battery Draw
Models:
2004-2007 Buick Rainier
2003-2008 Cadillac Escalade Models
2002-2008 Chevrolet TrailBlazer
2003-2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2002-2008 GMC Envoy Models
2003-2008 GMC Sierra, Yukon Models
2002-2004 Oldsmobile Bravada
2003-2008 HUMMER H2, H3
2005-2008 Saab 9-7X
Supercede:
This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 02-01-39-007A (Section 01 - HVAC).
When diagnosing battery draws on trucks equipped with the automatic dual zone HVAC controls (RPO CJ2), technicians should keep in mind that the control head does not completely "go to sleep" until after 150-250 minutes, or up to 4-1/4 hours, from when the ignition key is turned OFF. This is a normal condition. In these cases, DO NOT replace the control head.
...and perhaps one more....
A while back.... @Mooseman was explaining the A/C Portion of the HVAC system in the full sized SUVs to a Member once and he mentioned that there is a second "Mini-AC System" with its own compressor/condenser/evaporator unit in place to cool the passengers in the back of the vehicles... perhaps that unit is rapidly cycling on and off and causing the power drain...?
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I thought I would chime in with the SAIS thought...
This morning, the CEL light popped and I got P2444 and P2431 codes. While driving to work, I noticed the lights dimmend and cruise would kick off. It did this many times, to the point I said forget the cruise...I watched voltage gauge and it would drop from just over 14VDC to down to roughly 12VDC during this time (probably 1-2 sec). I did not time the frequency, but would guess anywhere between 30-60 seconds.
This morning, the CEL light popped and I got P2444 and P2431 codes. While driving to work, I noticed the lights dimmend and cruise would kick off. It did this many times, to the point I said forget the cruise...I watched voltage gauge and it would drop from just over 14VDC to down to roughly 12VDC during this time (probably 1-2 sec). I did not time the frequency, but would guess anywhere between 30-60 seconds.
smt 59
Member
I have a similar issue with another car. It comes from one failed rectifier in the back of the alternator. Perhaps your replacement alternator also has a similar problem.
If it was a used or refurb unit its entirely possible.
My headlights behave very similarly. Its worth the mention that the headlights, when in daytime running mode, are running at 70% via pulse width modulation(PWM) and they will appear to flicker if you look closely. When commanded to full brightness either by auto(and its dark) or manual selection of the headlamp switch they operate at 100% PWM.
Something else that makes all on my lights dim is the power windows. The lights dim when the window gets to the fully open or closed position. They dim a lot. Very effective on left lane interstate drivers to get them to move over. With the windows closed I pulse the up button on two windows five time in three seconds to produce a strobe like effect. The douche bag usually moves over.
Something else that makes all on my lights dim is the power windows. The lights dim when the window gets to the fully open or closed position. They dim a lot. Very effective on left lane interstate drivers to get them to move over. With the windows closed I pulse the up button on two windows five time in three seconds to produce a strobe like effect. The douche bag usually moves over.
- Jul 22, 2015
- 2,724
Thats pretty funny, making something useful out of a problem.
My windows are slow-moving; I've long had a habit (decades) of only raising / lowering one at a time, so as not to tax the battery. I shudder to think of how slow they'd be if I tried to move all 4 in the Voy at once.
My windows are slow-moving; I've long had a habit (decades) of only raising / lowering one at a time, so as not to tax the battery. I shudder to think of how slow they'd be if I tried to move all 4 in the Voy at once.
It wont make them lightning fast but cleaning and lubricating the window tracks and strip across the bottom with a silicone spray will reduce friction and speed them up some.
I too feel like the windows tax the battery too much when operating with the engine off. I leave the engine running until all windows are closed. Huge difference in speed. When I replaced my battery last year due to a slow crank, it did not speed the windows up with the engine shut off. Even a second battery connected in parallel did not do anything.
I too feel like the windows tax the battery too much when operating with the engine off. I leave the engine running until all windows are closed. Huge difference in speed. When I replaced my battery last year due to a slow crank, it did not speed the windows up with the engine shut off. Even a second battery connected in parallel did not do anything.
Or the size of the power wire to the door module. Think of the recall on the DDM catching fire when it got wet. Wires melted before the fuse popped. The wire can handle 10 seconds at so many amps but if you have a short causing a constant draw that is not enough to pop a fuse. Something has to give.