Strange Alternator Behavior - 3000GT/Stealth International Message Center
3000GT/Stealth International 3000GT/Stealth International
 

Auto Insurance

» Featured Product
Wheel & Tire Center

Go Back   3000GT/Stealth International Message Center > Automotive Discussions > General

3SI.org is the premier Mitsubishi 3000GT Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools
Old 02-25-2013, 08:58 AM   #1 (permalink)
Forum Member
 
3krazygt's Avatar
 
Join Date: Aug 2006
Location: Wisconsin
Drives: 92 R/T TT, 95 Spyder
3krazygt Level 13krazygt Level 1
Feedback Score: 57 reviews
Default Strange Alternator Behavior

I'm having a weird issue with my alternator on my 98 SL.

My setups is an alternator that appears to be good and an Optima red top. The car is essentially stock other than I did a Digital Climate Control conversion. I have my degree in electrical engineering and work for a company that does a lot of electrical assembly so I feel I did the conversion properly with quality splices and wire routing. I'm not sure if this issue occurred prior to doing the conversion, since I did the conversion right after buying the car with a blown motor, and hadn't started it until after the motor was swapped.

OK. So here is the behavior that is occurring. With a good battery in, the car starts up great. The car will idle with the voltmeter reading right around 14VDC. Right away this indicates the alternator is working properly, but just to make sure I removed (+) terminal from the battery to ensure the alternator is still working. When I removed it, the car ran normally verifying the alternator was good at idle.

When driving a different behavior occurs. Again when idle the car behaves normally. Then when ever I physically hit the gas, the car drops in voltage. It is apparent on both the voltmeter and visually as lights dim. It drops to approximately the voltage from the battery... so if fully charged (which the optima is brand new and is a fairly beastly battery) 12VDC.

There seems to be some issue with how the system is auctioneering power. Any out there with similar experiences? Any culprits to suggest?

Appreciate the help
__________________
Photo Sharing and Video Hosting at Photobucket
3krazygt is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 02-25-2013, 09:43 AM   #2 (permalink)
Verified Seller
 
BlackStealth's Avatar
 
Join Date: Apr 2000
Drives: 93 RT/TT
BlackStealth Level 1BlackStealth Level 1
Feedback Score: 244 reviews
Default Re: Strange Alternator Behavior

Quote:
Originally Posted by 3krazygt View Post
... just to make sure I removed (+) terminal from the battery to ensure the alternator is still working.
Bad idea, and is harmful to the voltage regulator. That technique you described only works on old school vehicles.

Also, temperature has an influence to the voltage regulator, higher voltage when cold.

Since you're good at electronics, you might consider rebuilding your alternator with new parts.
http://www.3si.org/forum/f4/alternat...t-75-a-542750/
BlackStealth is offline   Reply With Quote Quick reply to this message
Old 02-26-2013, 09:07 AM   #3 (permalink)
Forum Member
 
3krazygt's Avatar
 
Join Date: Aug 2006
Location: Wisconsin
Drives: 92 R/T TT, 95 Spyder
3krazygt Level 13krazygt Level 1
Feedback Score: 57 reviews
Default Re: Strange Alternator Behavior

Thanks for the reply. Just out of curiousity, could you elaborate on why that method would be harmful to the voltage regulator?

I see that the voltage regulator would see a difference of 2V, but i would imagine that it would be part of the voltage regulators duty to handle differences of 2V. Possibly a transient spike?

I'm a little familiar with working with voltage regulators, but I'm not an expert. So more info would be great. Do you you think the behavior I described would be a result of a bad voltage regulator? I kind of thought the gas-voltage relation was suspicous, and I thought maybe there was some sort of auctioneering circuit... something that switches between alternator voltage vs. battery voltage.
3krazygt is offline   Reply With Quote Quick reply to this message
Old 02-26-2013, 10:26 AM   #4 (permalink)
Verified Seller
 
BlackStealth's Avatar
 
Join Date: Apr 2000
Drives: 93 RT/TT
BlackStealth Level 1BlackStealth Level 1
Feedback Score: 244 reviews
Default Re: Strange Alternator Behavior

It's a well known fact that removing battery with engine running on a modern vehicle is a big no no. You can research it on google. My dad already learned this lesson, fried his voltage regulator, old school mechanic working on a newer vehicle.

A couple things that can go wrong on the alternator:
1. Worn brushes... when more load is demanded, it fails to deliver
2. Voltage regulator... incorrect charging voltages
3. Diodes...a failure can lead to battery premature draining when not in use, or the charging pulses are irregular and not providing full current.
BlackStealth is offline   Reply With Quote Quick reply to this message
Old 02-26-2013, 05:55 PM   #5 (permalink)
Forum Member
 
twinblown's Avatar
 
Join Date: Oct 2003
Location: Central Florida
Drives: Sole Survivor
twinblown is an unknown quantity at this point
Feedback Score: 10 reviews
Default Re: Strange Alternator Behavior

When you remove the battery + in a running system It's called "load dump" ; in modern vehicles it can be very harmfull to the extent that it will damage the regulator due to the transient voltage spike created. The Alternators in these cars operate on the highside ("A" type) and removing the B+ is more detrimental to causing damage. You do not mention where are you taking the voltage readings; if you are going by the gauge you should know they are not accurate ; take more accurate readings at the battery post and even better ones at the Alternator B+ (be carefull). If you are not having crank issues then your system is charging properly. good luck
twinblown is offline   Reply With Quote Quick reply to this message
Old 02-26-2013, 07:32 PM   #6 (permalink)
Curmudgeon
 
Steve '93ES's Avatar
 
Join Date: Sep 1999
Location: Southern NH
Drives: '92 ES, '92 TT
Steve '93ES Level 2Steve '93ES Level 2Steve '93ES Level 2Steve '93ES Level 2Steve '93ES Level 2
Feedback Score: 2 reviews
Default Re: Strange Alternator Behavior

Have you checked the obvious? If the belt is loose it could be slipping under higher RPMs.

Quote:
I thought maybe there was some sort of auctioneering circuit... something that switches between alternator voltage vs. battery voltage.
Nope.

Removing the battery with the engine running can do more than damage the regulator. It can also damage the ECU and any other electronics in the car. It's not just the transient spike (which is the major problem) but also that the battery works as a filter cleaning up the normally noisy output from the alternator. People argue back and forth on this but I'm in the "don't do it" camp.
Steve '93ES is online now   Reply With Quote Quick reply to this message
Old 02-27-2013, 07:33 PM   #7 (permalink)
Forum Member
 
Escape-Performance's Avatar
 
Join Date: Aug 2010
Location: Vermont
Drives: lots
Escape-Performance is an unknown quantity at this point
Feedback Score: 11 reviews
Default Re: Strange Alternator Behavior

I have seen bad alternators do this. Work at idle, stop working as the rpm goes up.
__________________
Single Holset HX52 with custom quick spool valve
Escape-Performance is offline   Reply With Quote Quick reply to this message
Old 06-20-2013, 07:49 PM   #8 (permalink)
3SNY - HondaTurtleFTW
 
FluffyCow's Avatar
 
Join Date: May 2007
Location: West Islip, NY
Drives: 92 VR-4
FluffyCow is an unknown quantity at this point
Feedback Score: 11 reviews
Default Re: Strange Alternator Behavior

Bump. My Alt is outputting 13.6v at idle. When revving with throttle cable it stays at 13.6. Is my alt bad?

Sent from AutoGuide.com Free App
__________________

1991 Dodge Stealth ES
- The car that started the 3S obsession
Mods: Open air filter, "resonator" bottle removed

1991 Fiji/Mystic Blue R/T TT 1 of 235(paint/R/T TT only, can't find more info, VIN is a 1 of none number)
Sold 6/19/11 to my923ksl
1992 silver VR-4 - 1 of 152 identical
Show: 99 Sails, 99 rear garnish, 2nd-gen steering wheel, Kaze exhaust cover, Pioneer Premier h/u, aftermarket speakers(Alpine type s's I think), 10 inch JL W1 sub in spnallb corner box.
Go: 15G Turbos, FMIC, ATR DP, ACT clutch, 3-inch singleshot(Currently off car due to bottoming out), no cats, HKS SSQV BOV, PWR rad, Ksport coilovers, 3sx rear adj. control arms, fECU w/ FPR solenoid as BCS, Cianci gauge pod w/ Defi D-series(Boost, EGT, oil pres), 93 shifter.

1987 Dodge Ramcharger - The back-up plan. Mods: Non-computerized timing, custom white gauge faces and red LED illumination, cat-back straight pipe, Chevy seats, Ford running boards, and Mopar everything else.
Wife's ride: 2014 Hyundai Sonata 2.0T --still waiting for permission to mod.
FluffyCow is online now   Reply With Quote Quick reply to this message
Old 06-21-2013, 01:07 PM   #9 (permalink)
Verified Seller
 
BlackStealth's Avatar
 
Join Date: Apr 2000
Drives: 93 RT/TT
BlackStealth Level 1BlackStealth Level 1
Feedback Score: 244 reviews
Default Re: Strange Alternator Behavior

Quote:
Originally Posted by FluffyCow View Post
Bump. My Alt is outputting 13.6v at idle. When revving with throttle cable it stays at 13.6. Is my alt bad?

Sent from AutoGuide.com Free App
No, that is normal so far.
BlackStealth is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

  3000GT/Stealth International Message Center > Automotive Discussions > General

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the 3000GT/Stealth International Message Center forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
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.
Free email addresses do not work(yahoo, hotmail, gmail,...)
We are currently being blocked by AOL so any AOL based address may not work(aol.com, aim.com, netscape.net, cs.com)
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.



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 On
Trackbacks are On
Pingbacks are On
Refbacks are On


Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 07:21 PM.




Garage Plus vBulletin Plugins by Drive Thru Online, Inc.

Search Engine Optimization by vBSEO 3.3.2