weird electrical? issue... flickering lights and low voltage at times...

[Exibar]

Ok, so here's What I've done to the truck (yah, before I describe the problem) ;-)   Problem was with the Avvy before I performed these things too...
  
1) I had to replace the dash gauges due to the known issue with the gauge cluster going out at random times.  The entire gauge cluster would only come on when it felt like it.
2) after replacing the instrument cluster I noticed that the "flickering" problem was still there, and I had somewhat low voltage at times under load (see below too) (A/C on, High Beams on) so I figure the alternator was on it's way out, or at least the voltage regulator within the Alternator.
 So I replaced the alternator, 135amp unit 12oclock connector.
3) I replaced the drive belt along with the Alt too.
4) Battery is brand new Sears Die hard gold 724CCA, 'bout a month maybe month and a half old.

  So now this problem is still there.  When I put on my lights at nigh they kinda flicker a bit, dash lights/console lights/heated seat and window switch lights....  it's noticable, but just a bit noticeable...  it's for sure a flicker, the kids see it too ;-(
   If I try to put two windows down at the same time, any two windows, and keep both switches engaged after the windows go up or down, I can watch the volt meter drop to about zero and then all kinds of bells ring and dinging occurs until I let off of the swtich.  This happens whether or not I have a high load on the truck...  so if I have all lights/AC/radio/etc turned off, and hold two window switches up or down I can re-create this condition.

   Is there a separate voltage regulator in the truck other than within the alternator?  
  anyone see this danged problem before?  It's so annoying and I'm concerned that it's just the tip of the iceberg.  
  avvy is a 2003 ZL1 package loaded with all the toys...  the only brand new vehicle I've ever bought and I just love my Avvy, but this problem is making it hard for me to convince the wife that the Avvy is still dependable ;-(

  any help would be greatly apreaciated!

  thanks all!

    Mike B

[Exibar]

oh yah, and the truck seems to idle kinda low at times...  less than 500rpm...  she never stalls, but just seems to go down to that really low RPM after taking my foot off the gas, predominately for turns... but not exclusevly.

  The "window down" test occurs at all speeds, and all RPM's sitting in the driveway.  so even if I rev up the engine, I can make the voltage meter go all the way down to the left if I move 2 windows up or down and hold the two buttons..

 Mike B

[MS03 2500]

Sounds like a ground issue. Also I know a GM ALT comes in 105 and 145 amps. Which 135 did you buy,

[Exibar]

Must have been the 145 amp unit and I mis-remembered....  Got it from autozone, non-reman brand new unit.

[MS03 2500]

I would check the ground wire from the battery to the frame.

[Exibar]

Hmmm....  you know that makes sense...  under the high load of two windows trying to move the bad ground shows up more clearly....

  Must be easy to find if it goes from the battery to the frame too...  I'll check it out in the morning and let you know if it fixes the problem

 thanks!
 Mike B

[Alaska_AV.]

check the one to the engine also

[MS03 2500]

check the one to the engine also

Good point.

[AVArookie]

So what did you come up with?

[Exibar]

After checking the grounds it's still there, although it's a bit better....  still annoying though....   there's an alternator electrical change thing that I want to do, It's adding a different plug to the back of the alternator and making a slight wring change... I'll have to look it up again for the particulars, just haven't had a chance to get to doing it yet....

 even holding two wind buttons up or down on the highway, after about 20 seconds the voltmeter drops almost all the way down, the 4 wheel drive warning comeson and a bunch of other warning lights.... let go of the two switches and everything jumps back to normal... it's the wierdest thing...

 Mike B

[Mardela]

High voltage fuse is the problem

[Exibar]

High voltage fuse huh?   Hmmm, are you saying that it's blown?   I'll have to take a look at it, is it actually labeled as "high voltage fuse" and is it in the fuse / relay box?

 the problem is certainly much more pronounceable with the A/C turned on too...


  sounds like Avvrookie and I both have the exact same problem.... Rookie, if you pull up on two window switches at the same time for about 10 - 20 seconds, do all your inidcator light start blinking and beeping?

 thanks!
 Mike B

[MS03 2500]

Have you added any electrical mods to it. Like a different radio/nav

[Exibar]

Have you added any electrical mods to it. Like a different radio/nav

 nope, no mods to it....   new alternator & belt, new A/C pump, and new battery  :-(

[MS03 2500]

I can only tell you from my experience with my 03, it was the Alt and I upgraded to a 145 amp from the snow plow package.

However, if the RPMs drop below 500 rpm yes the light will dim. On computer control car you will have all sorts of problems if the voltage gets too low.

So try the cheap fixes first

1 Look on the frame rail on the driver side and see if you have a external fuel filter, if you have one change it

2 Clean your MAF

How many miles on it and have you changed the spark plugs and wires.

A tuned up AV is a happy AV.

[Mardela]

I had the same problem and the dealer repaired it.  I'll dig out my paperwork and give you the exact part number and location.  If the dash blanks out, doors lock and unlock, it's this fuse.  If the display loses it's memory, like trip od resets, then it's the gauge cluster.  Sometime the HV fuse causes both.

[Mardela]

my part # for 2009 5.3 flex is 15305191.  175 amp fuse on the firewall by the battery.  Replace this if your doors are locking and unlocking, display blanks out, ect.

if the memory function of the instrument panel resets after above symptoms, replace instrument gauge cluster as well.