All lights surging/dimming

[pejeeper]

I have searched and sought advice from similar threads but my problem is a bit different and persists, so I am starting my own thread....


All lights on my 05 TB LS "flash" intermittently. This first happened a month ago. I have since replaced my battery. I have not noticed any "flashing/flickering" since replacing it until today.

I turned on the volt meter on my radar detector when I noticed it this morning. Normal running voltage registered at 14.2/14.3 (the numbers probably aren't accurate but the important part is what follows)..when the flickering starts, the volt meter shows a SURGE to 15.8/15.9 volts and then a drop to 12.5/12.6 volts. This surge/drop happens about 7 or 8 times over 20-30 seconds and the volts return back to normal for 5-10 minutes.

This affects headlights, tail lights, interior lights, dash lights, radio lights. It does not affect blinkers or hazards. The surging does not happen at idle, seems to kick up around 1000 RPMs and up. Nothing I do seems to make it worse or better(i.e. turning off radio, blower fan, headlights, turning on the AC, all interior lights, hi-beams). Load on the electrical system doesnt seem to be a factor.

Performance is not affected either, idle, power, RPMs do not feel different during the surging episodes.

Is there a single relay that controls all these lights?

 

[The_Roadie]

No common thread except the alternator. Nothing the battery can do will make a voltage increase happen. Since the voltage regulator is built into the alternator, there is no external wiring issue or bad regulator that can cause this.

 

[pejeeper]

That's kinda what I was thinking too, but wasn't quite sure. I figured maybe a failing relay was allowing a surge through or the alternator was creating unstable output.

 

[The_Roadie]

Lights do indeed go through relays, fuses, and some go through the ignition switch. But the main battery bus (not switched by the ignition switch) is the common circuit behind everything, and the alternator's output is tied to that honkin' red wire.

If you had a DIMMING that happened exactly three times, one second apart, 5-15 minutes after a cold start, that would be the SAIS diagnostic test. But it should not go above 15.0-15.5 V ever.

 

[pejeeper]

Lights do indeed go through relays, fuses, and some go through the ignition switch. But the main battery bus (not switched by the ignition switch) is the common circuit behind everything, and the alternator's output is tied to that honkin' red wire.

If you had a DIMMING that happened exactly three times, one second apart, 5-15 minutes after a cold start, that would be the SAIS diagnostic test. But it should not go above 15.0-15.5 V ever.

I know the SAIS test that causes the flicker...I get that every morning.

I was quite surprised to see the power surging though. I guess I'll throw a new alternator at it and see what happens. Not too concerned about the $, the TB hasn't cost me much more than maintenance.

 

[delcobose]

I have flickering with my 05 Envoy and it seems to be caused by the secondary air pump cycling.

 

[winger1969]

That's kinda what I was thinking too, but wasn't quite sure. I figured maybe a failing relay was allowing a surge through or the alternator was creating unstable output.

I'm assuming you got this fixed. mine was doing the same, at idle, lights were fine, acceleration in neutral or drive caused a strobe effect with ALL lights, interior and exterior. local autozone guy told me he thought it was diode in alternator, bought one and it fixed problem. old alt. was charging the system great, just had bad diode.

 

[Wooluf1952]

I'm assuming you got this fixed. mine was doing the same, at idle, lights were fine, acceleration in neutral or drive caused a strobe effect with ALL lights, interior and exterior. local autozone guy told me he thought it was diode in alternator, bought one and it fixed problem. old alt. was charging the system great, just had bad diode.

Thanks for the input and:

Welcome

In case you haven't heard:
http://gmtnation.com...eres-the-story/

 

[winger1969]

Thanks for the input and:

Welcome

In case you haven't heard:
http://gmtnation.com...eres-the-story/

thank you, just had been reading up til this point

 

[pejeeper]

havent logged into GMTNation in a long time...lots going on

anyway, TB has been just fine...random/intermittent flickering or dimming still happens, but since I don't do a lot of night driving, I can't tell how often it's really happening. I used to notice it mainly in the dark mornings on my way to work.

It doesn't seem to be affecting any other systems, so if it an alternator, I guess I'll find out when it finally does.

Thanks!!