2006 Chevy Tahoe High output voltage

4VLAD

MEMBER
2006 CHEVROLET TAHOE
V8
4WD
AUTOMATIC
56,000 MILES

Hello, my 2006 Chevy Tahoe is registering 15.2- 15.6V during idle. I understand there is some margin for the actual meter reading in the dash. The meter and a Fluke 787 meter read virtually the same. In my estimation this is much too high and can result in electronic system failures. The GM dealer has told me is in spec because no error has been recorded by the on-board computer.
How can I convince these non-technical technicians this is a big problem and needs to be corrected?

Please help,
Vlad

3 Replies

CARADIODOC

MECHANIC
33,871 POSTS

No need to panic. 13.75 to 14.75 volts has always been the standard we teach, but in may cases, GM systems can go a little higher because their batteries, (remember the old "Freedom" batteries from the 1970s?), Can handle the higher voltage without boiling the water out of the electrolyte.

The voltage regulator is inside the generator, so you would have to replace the generator to see if the voltage would come down a little, but in this case, I don't think I'd worry too much about what you have.

It IS nice to know your dash gauge is real accurate.

Caradiodoc

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Tuesday, March 16th, 2010 AT 4:41 PM

4VLAD

MEMBER
2 POSTS

Hello caradiodoc, Thank you for your response.
I wouldn't worry except this condition suddenly popped up. For years the meter in the dash registered between 13 and 14 volts.
When the voltage went high, I was driving on a highway at night and noticed the lighting suddenly got brighter. Since then the voltage has been high (most of the time).
I've already replace 2 center stop light bar's, and one head light. I'm sure there is a problem and my electronics will suffer, I just hope they fix it before things really start going bad. They tried to convince me the battery was bad, yet their tests should otherwise. I'm looking for a GM specification regarding the voltage.
Regards,
Vlad

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Tuesday, March 16th, 2010 AT 4:51 PM

CARADIODOC

MECHANIC
33,871 POSTS

Look at the small 4-pin connector on the side of the generator's case. If there is a single brown or red wire, (I can't remember), the voltage regulator gets its sensing voltage from the output wire. If there is a second wire in the plug, system voltage is sensed in the instrument cluster. This is done with digital dashes because the voltage there is more critical to prevent flickering brightness. There can be a different second wire, (white as I recall, but not certain), that is used for a tach signal for diesels.

Based on your previous knowledge, I would replace the generator, then, if the voltage comes back to normal, trot over to the dealer and stick their noses under the hood. Unlike the older generators from the 70s and early '80s, the voltage regulator is real hard to replace in the '87 and newer units, but it isn't impossible.

If you have a second wire in the plug, you might try disconnecting the plug, then run a wire from the battery positive through a small 12 volt light bulb to the generator terminal corresponding to the red or brown wire. You could also just remove the second wire from the plug if you can get it out without destroying it. It should regulate voltage internally this way. If the voltage comes down, look for a break in that second wire. I might be getting confused, because an open wire would be interpretted no differently as no wire at all. Perhaps low voltage, maybe due to a corroded connector pin, would make more sense.

I probably shouldn't be talking about that second wire since I don't know what goes on inside the voltage regulator's mind.

Caradiodoc

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Tuesday, March 16th, 2010 AT 5:19 PM