Overcharging alternator

[jlahood]

Alternator on my 07 Trailblazer is overcharging. It will run at about 14 to 15.5. Sometimes it will be at 12.5 to 13 which I think is normal. I noticed on long freeway drives it will eventually drop down to the normal range. Does overcharging cause problems? Does it effect how the fuel injectors work? Bad fuel mileage?
Thanks for your help.

 

[blazinlow89]

"Normal" is 14.4V

Sounds like it could be going bad. Or you have a slipping belt.

Do you have any aftermarket stuff, stereo, subs, amp, lighting, etc?

 

[Voymom]

"Normal" is 14.4V

Sounds like it could be going bad. Or you have a slipping belt.

Do you have any aftermarket stuff, stereo, subs, amp, lighting, etc?

SHHHHH Don't say that!! LOL

Spoiler

I guess I have to add another TO DO on my already forever long TO DO list for the Envoy

 

[jlahood]

"Normal" is 14.4V

Sounds like it could be going bad. Or you have a slipping belt.

Do you have any aftermarket stuff, stereo, subs, amp, lighting, etc?

No everything is stock. I plan on replacing it, but it will be a couple of weeks. Just want to make sure it won't mess anything up by waiting.

 

[Simon01]

Are you going by what the dash gauges say? I wouldn't really trust their accuracy. If the alternator is really overcharging, I have seen batteries boil. If you think there is a problem with it, have it checked out at a shop or take it off and have it tested at Autozone or parts store of your choice.

 

[Sparky]

FWIW it could be higher voltage to charge the battery, but then on a long trip the battery reaches "full" so it drops the voltage some to a maintenance level. Just a thought.

 

[The_Roadie]

In my experience, 15.0V+ is never a reasonable number to see on a real meter. Dash gauge can lie. A scangauge that looks at the data stream is another alternative to having a real meter hooked up. But at $5 or less at Harbor Freight or Radio Shack on sale, there's no excuse for not owning a meter or two.

Since the voltage regulator is built into the alternator, the culprit is clear. A slipping belt can give you lower RPM and perhaps lower voltage at idle, but above 1000 RPM that's not a possible suspect. Slipping belt can never give you too-high voltage.

 

[HTUSA]

I have an 08 and the gauge will read 15+ volts. The scan gauge is only reading 13-14volts.
The dash gauge will settle down after drving long distances.
I am postive that the dash gauge is lying to us.

 

[blazinlow89]

That's why I was going with slipping belt, due to the factory gauges accuracy. The voltage regulator was my other guess, forgot to put it in my post.