[7/17] Huge Voltage Fluctuation - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



Welcome Enthusiast! If you already own a Chevy TrailBlazer or GMC Envoy or perhaps thinking of purchasing such a vehicle, then you have come to the best TrailBlazer and Envoy site on the net! Rainier, Bravada, Ascender, and 9-7x owners welcome too!

You are currently viewing our site as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to search and post topics, communicate privately with other members, respond to polls, upload content, and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.
Join Today!
Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain

02-09 Vortec 4.2L I-6 Engine and Drivetrain Q&A forum for engine and drivetrain repairs/modifications/tuning.

TrailVoy.com is the premier GMC Envoy Forum on the internet. Registered Users do not see the above ads.
 
 
Thread Tools
  #1  
Old 07-17-2007, 11:04 AM
05Envoy05's Avatar
05Envoy05 05Envoy05 is offline
Junior Member
 
2005 GMC Envoy SLT
Forest Green Metallic 4.2L I6 4X4
Join Date: Jun 2007
Location: Savannah, Georgia
Posts: 41
Unhappy [7/17] Huge Voltage Fluctuation

Ok, so I have a Large fluctuation in the voltage meter while driving. It seems to only happen on de-acceleration. But, when it happens it drops and then comes back higher than it runs (12 volts)....Then it levels out at 12 all within maybe 3-5 seconds. I tested the battery for voltage and it seems fine. I have no mods to my vehicle except for a Sirius Satellite Radio. I really need to figure this out because driving at night it seems that my car is flashing people.

I recently changed the A.I.R. System check engine valve because I had an error code that asked for me to change that or the air pump. This voltage drop was happening before I did any repairs. I tested the Pump and it's fine. I have no Service code light or codes as of now.

Thanks!
Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 07-17-2007, 11:09 AM
markhart1's Avatar
markhart1 markhart1 is offline
Junior Member
 
2005 Chevy TrailBlazer LS
Silverstone Metallic 4.2L I6 4X4
Join Date: Dec 2005
Posts: 42
Check out this previous thread:
http://forums.trailvoy.com/showthread.php?t=25432
Quick reply to this message
  #3  
Old 07-17-2007, 11:41 AM
jimmyjam's Avatar
jimmyjam jimmyjam is offline
TrailVoy Guru
 
2006 Chevy TrailBlazer SS (LT)
White 402ci Other AWD
Join Date: Jun 2005
Location: clearwater fl
Posts: 5,895
are you sure that the voltage is around 12v at idle? should be around 13.8-14V when the alternator is running. might be a bad regulator in your alt.
Quick reply to this message
  #4  
Old 07-17-2007, 04:48 PM
05Envoy05's Avatar
05Envoy05 05Envoy05 is offline
Junior Member
 
2005 GMC Envoy SLT
Forest Green Metallic 4.2L I6 4X4
Join Date: Jun 2007
Location: Savannah, Georgia
Posts: 41
Ok......First off my voltage is 12v at off and 14v while on. But the problem only happens when driving and only when de-accelerating. Secondly....I recently replaced the Check Valve (solenoid) because I had the check engine light on for the A.I.R. system. I tested the air pump and it's in working order. Tested the alternator (AutoZone), cleaned the wires/cables and still am having the problem. Any more ideas?
Quick reply to this message
  #5  
Old 07-17-2007, 07:02 PM
neelskit's Avatar
neelskit neelskit is offline
Member
 
2002 Chevy TrailBlazer LT EXT
Pewter Metallic 4.2L I6 4X4
Join Date: Jul 2007
Location: Cicero, IN
Posts: 365
Quote:
Originally Posted by 05Envoy05 View Post
...Tested the alternator (AutoZone)...
When AuoZone tested you alternator, was the voltage fluctuating? If not, then I think jimmyjam is on the right track with a bad voltage regulator in the alternator. The alternator may have passed AutoZone's test because the voltage regulator could have an intermittent problem.

Just a thought...
Quick reply to this message
  #6  
Old 07-17-2007, 11:33 PM
jimmyjam's Avatar
jimmyjam jimmyjam is offline
TrailVoy Guru
 
2006 Chevy TrailBlazer SS (LT)
White 402ci Other AWD
Join Date: Jun 2005
Location: clearwater fl
Posts: 5,895
is the voltage dropping below 12V? can you quantify it a little more, also when you say you are decelerating, is it when you pressing the brakes or just letting off of the gas?
Quick reply to this message
  #7  
Old 07-18-2007, 06:18 AM
PROSPHOTO's Avatar
PROSPHOTO PROSPHOTO is offline
TrailVoy Alumni
 
2006 Chevy TrailBlazer LT
Superior Blue Metallic 4.2L I6 4X4
Join Date: Jan 2007
Location: Selden, NY
Posts: 3,497
It's possible that you have a loose ground somewhere, and when you're decelerating it's just the right stress to affect the connection
__________________
-Mike
Car Domain
AKA PROVY Rock On!
Quick reply to this message
  #8  
Old 07-18-2007, 01:23 PM
05Envoy05's Avatar
05Envoy05 05Envoy05 is offline
Junior Member
 
2005 GMC Envoy SLT
Forest Green Metallic 4.2L I6 4X4
Join Date: Jun 2007
Location: Savannah, Georgia
Posts: 41
1.) Couldn't tell ya for sure on what AutoZone said, I had someone take it up there for me while I was working. I just know they said it passed.

2.) Yes it's dropping below 12Volts on the dash...then it recovers over 12volts (where it usually is) up to about 13-14 volts and then levels out, all of this happening within only a few seconds. It happens when I take my foot off the gas, no matter if I am breaking or not.

3.) I have checked all of the grounds under the hood and have found nothing loose, I tightened them all up but they are all tight.

4.) I did try something someone suggested with putting something in between a ground and power wire that run under the hood. I am going to see if for some reason that works to fix the problem. I drove around my sub-division last night and didn't get the problem. But somedays it happens a lot more than others so who knows.

I will post whether or not this fixed the problem!
Quick reply to this message
  #9  
Old 07-18-2007, 09:06 PM
philba1111 philba1111 is offline
Junior Member
 
2002 Chevy TrailBlazer LT
Indigo Blue Metallic 4.2L I6 4X4
Join Date: Sep 2005
Location: Bohemia, NY
Posts: 13
How do you know that you are running at 13 or 14 volts? Are you testing with a multimeter at the battery connection? If not, I would suggest taking a multimeter, measure voltage at the terminals while the vehicle is running. Keep the prongs connected, and have an assistant accelerate, and decelerate with the vehicle in park of course. Let us know what your readings are.

Vehicle off, battery should measure at 12.6v
vehicle running, should measure at approx. 14.46.

My quess without following the diagnostic chart, which would involve use of a good scan tool such as the Solus, would be weak altenator. I wouldn't trust an auto parts store to make a diagnosis. How did they test your altenator? With a vat 40? or did you take the part out and have them bench test it?
Quick reply to this message
  #10  
Old 07-18-2007, 10:54 PM
garym1a2 garym1a2 is offline
Junior Member
 
2002 Chevy TrailBlazer LS
Liquid Silver Metallic 4.2L I6 4X4
Join Date: Jan 2006
Location: Orlando, FL
Posts: 36
Quote:
Originally Posted by 05Envoy05 View Post
1.) Couldn't tell ya for sure on what AutoZone said, I had someone take it up there for me while I was working. I just know they said it passed.

2.) Yes it's dropping below 12Volts on the dash...then it recovers over 12volts (where it usually is) up to about 13-14 volts and then levels out, all of this happening within only a few seconds. It happens when I take my foot off the gas, no matter if I am breaking or not.

3.) I have checked all of the grounds under the hood and have found nothing loose, I tightened them all up but they are all tight.

4.) I did try something someone suggested with putting something in between a ground and power wire that run under the hood. I am going to see if for some reason that works to fix the problem. I drove around my sub-division last night and didn't get the problem. But somedays it happens a lot more than others so who knows.

I will post whether or not this fixed the problem!
Nothing wrong with your alternator, most late model GM alternators work this way, at low RPM they slow the response rate of the alternator so that sudden load changes will not affect engine rpm. Take you truck during daytime and turn off the headlights than turn them on, you will see the voltmeter dip for one second. This feature is called "load response control"
If you increase your engine speed and vary electric loads you will never see it.
Quick reply to this message
Sponsored Links
Advertisement
 
 

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum forums, you must first register.

Please enter your desired user name, your email address and other required details in the form below.
(Only letters, numbers, dashes and underscores are permitted for user names)
The user name that you choose is permanent and can never be changed.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
1133 1135 Codes Help? ltz03 OEM Issues 6 08-19-2009 10:33 AM
Need wiring diagrams LeonPhelps Audio and Electronics 4 03-21-2009 03:31 PM
Engine swap questions kingkilburn Engine Tunes/Mods 61 08-02-2008 08:01 PM
Check Engine Light (UH OH) 05Envoy05 02-09 Vortec 4.2L I-6 Engine and Drivetrain 34 07-07-2007 05:26 PM
A Huge Thanks to Vengeance! FASTONE27 Southeast 0 03-08-2007 07:03 AM


» Sponsors

Advertising Info

All times are GMT -4. The time now is 04:00 PM.


Chevy TrailBlazer and GMC Envoy Enthusiasts - Copyright 2004 - 2009 All Rights Reserved.
All trademarks referenced herein are property of their respective owners.
RSS Feed