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Strange electrical problem....

O

Oxsign

Full Member
Joined
Dec 7, 2011
Messages
240
Location
Orlando FL
So 3 different times now over the last 2 months. My truck will be fine charging properly and then out of nowhere it?ll start acting like it has a d ad battery. So I went out and bought a new battery, had my alt tested etc and everything is good again. A few weeks later, same thing. I changed my crankshaft position sensor and everything is good again. A few weeks later, same thing. This time I disconnect everything (alt, battery, starter, etc) and tested the battery and it?s resting at 12.6. Took the alt and starter back in again tiger tested and everything checks out good. I reconnected everything and we?re good again. But for how long?? What else could be the issue?? Voltage regulator?? It just seems like when I disconnect it resets and it?s good again for a couple weeks. I?m kinda at a loss....
 
  Could be internal with alternator. Being it is intermittent. When it happens you could
do a Parasitic Draw Test. You Tube it there are good tutorials.
 
Chances are the place that is testing your alternator is not doing a full test. You likely have 1 diode bad. Most testers just look at the voltage and if only one diode of the 4 is bad you only have half an alternator.

Half an alternator works OK until you have to drive with your lights on... What does your volt meter say when your driving? It should NOT drop if you turn on your lights, heated seats etc... I would try turning on everything you can and see if the voltage is different then when nothing is on. If it does then you definitely have a bad diode in the alternator and need to get a new one.

The problem when you loose just one diode is that the other side is fine. So you will have good voltage on their meter but won't handle a load. And if you were to look at the waveform it is putting out it would be almost like a dashed line instead of a solid line. (Not a true dashed line because the voltage just drops. ) Some shop testers only detect if a diode on each phase is out.

A standard Alternator makes AC current so what they do is they basically put 4 diodes into the alternator in a pattern that smooths out the output into a pretty solid line. Not perfect but with few openings. The battery is used to smooth out this ragged line. When a diode is blown those drop outs or openings as I mentioned earlier get longer. If the tester they are using just checks the voltage then it will never see this. Especially if in vehicle.

 
When it is acting up, is there any power at all? Like, do dome lights or door locks work? Just won't crank? Or totally 100% completely?

I had an 07 Tahoe that would go totally dead some times. Apparently the problem isn't uncommon for 07+ GM full sizes, and typically traces to a bad ground. Some people will actually have issues with door locks and dash gauges going crazy while driving down the road.
Someone with the problems: https://www.youtube.com/watch?v=TBBRGkMlM_g
This guy talking about his problems and replacing the ground cable: https://www.youtube.com/watch?v=27WUPHZnOOs

If that is it, there's also a mega fuse mounted on the firewall close on the passenger side, close to the battery. Might check that for any corrosion.
 
DESCRIBE what it is doing when you think it is bad.....
 
I know this is an older post.  However, my 2005 1500 Avalanche has a newer used 200 amp alternator.  When driving lately, the meter on the console will show about 9 volts at times and other times 15 volts.  I was thinking of replacing the voltage regulator.  I have checked my ground straps and battery terminal/connections.  Suggestions?  Comments?  As always, thank you.
 
If you measure with a volt meter when the gauge shows 9 volts or 15 volts, what does you volt meter show?
 
Kind of having the same problem here. Every time My Avalanche would sit for 3 days or more the battery would be dead. Tested Alt. & battery , they were fine. Did some reading and watched some videos. Come to find out my instrument cluster was causing a parasitic draw on my battery. Shipped it out for repair because a replacement is very costly. I am expecting it back today.
 
speedy03 said:
Kind of having the same problem here. Every time My Avalanche would sit for 3 days or more the battery would be dead. Tested Alt. & battery , they were fine. Did some reading and watched some videos. Come to find out my instrument cluster was causing a parasitic draw on my battery. Shipped it out for repair because a replacement is very costly. I am expecting it back today.
Click to expand...

The instrument cluster in my 2004 EXT did this exact same thing.

If the truck sat for several days undriven, the battery would be drawn down pretty low.

I once made my way past the driver's side window in the totally dark garage and I could see faint gibberish characters glowing in the DIC display.

Later, all of the gauges began to randomly read the same amount lower than what they should have been reading.

The speedo and tach read correctly, everything else read the same distance low on their gauge.

I replaced my cluster with an upgraded unit and all of the issues went away, including the battery draw down.
 
Gator6 said:
I know this is an older post.  However, my 2005 1500 Avalanche has a newer used 200 amp alternator.  When driving lately, the meter on the console will show about 9 volts at times and other times 15 volts.  I was thinking of replacing the voltage regulator.  I have checked my ground straps and battery terminal/connections.  Suggestions?  Comments?  As always, thank you.
Click to expand...

I'm curious why did you add a 200 amp alternator they are not plug and play
 
EXT4ME said:
The instrument cluster in my 2004 EXT did this exact same thing.

If the truck sat for several days undriven, the battery would be drawn down pretty low.

I once made my way past the driver's side window in the totally dark garage and I could see faint gibberish characters glowing in the DIC display.

Later, all of the gauges began to randomly read the same amount lower than what they should have been reading.

The speedo and tach read correctly, everything else read the same distance low on their gauge.

I replaced my cluster with an upgraded unit and all of the issues went away, including the battery draw down.
Click to expand...

Installed cluster back in and everything is working great. I also paid a little extra for them to upgrade the lights to LEDs and I really like how bright it is now. $129 + shipping to them was more affordable than a replacement for me. Not to mention they send it back with a lifetime warranty.
 
Outstanding!

(y)
 
speedy03 said:
Installed cluster back in and everything is working great. I also paid a little extra for them to upgrade the lights to LEDs and I really like how bright it is now. $129 + shipping to them was more affordable than a replacement for me. Not to mention they send it back with a lifetime warranty.
Click to expand...
Nice! What company did the work?
 
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