Volt meter melting on negative + negative strap? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 03-13-2013, 02:44 AM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
Volt meter melting on negative + negative strap?

Hey guys me again, I replaced wiring and alternator after my initial 'smoke' problem.

Mutli-meter is in 10AMP unfused DC10 mode.

Right now (did not plug in battery fully because I think there is still at issue) if I unplug alternator from main positive lead and run meter across negative strap and negative post on the battery car flashes lights (normal when power is restored) and it's all good.

I plug alternator back in and multi-meter starts to smoke as soon as I make same connection as above.

Wiring is new... alternator is new. Am I not using multi-meter right? From what I understand this is a sign of a bad ground because I don't see why plugging in alternator would cause multi meter to overload if car is stationary.


    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 03-13-2013, 04:52 AM
EOD Guy's Avatar
Registered User
 
Last photo:
Join Date: Aug 2010
Location: Alabama
Posts: 2,145
Wiki Edits: 0

Thanks: 1
Thanked 156 Times in 144 Posts
If you unplug the main charge wire from the alt and the battery and all is well. When you plug it back in and get a short.......... the wire is rubbed thru somewhere and shorting to ground.
Reply With Quote Quick reply to this message
The Following User Says Thank You to EOD Guy For This Useful Post:
Aleksey (03-13-2013)
  #3 (permalink)  
Old 03-13-2013, 09:44 AM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
Quote:
Originally Posted by EOD Guy View Post
If you unplug the main charge wire from the alt and the battery and all is well. When you plug it back in and get a short.......... the wire is rubbed thru somewhere and shorting to ground.
If alternator and starter ground via cross frame could that cause this too? I'm 100% positive main wire is not exposed anywhere but the connections.

Also, am I assumption correct that volt meter should behave exactly the same with alternator plugged in the circuit?


Thanks!
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 03-13-2013, 11:21 AM
sedanbob's Avatar
Registered User
 
Last photo:
Join Date: Oct 2008
Location: St. Louis
Age: 66
Posts: 626
Wiki Edits: 0

Thanks: 61
Thanked 80 Times in 77 Posts
If I am reading this correctly, with the alternator disconnected and the meter in-line between the battery and battery cable - the meter makes the connection and the amp draw is less than the meter can handle, but when the alternator is connected and the meter is in-line between the alternator and the positive cable on the battery, the meter makes the connection and immediately starts smoking. If I read that right, it makes sense - the meter is attempting to measure the amp flow from the alternator which is likely way above the 10amp setting on your meter!
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 03-13-2013, 12:35 PM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
Quote:
Originally Posted by sedanbob View Post
If I am reading this correctly, with the alternator disconnected and the meter in-line between the battery and battery cable - the meter makes the connection and the amp draw is less than the meter can handle, but when the alternator is connected and the meter is in-line between the alternator and the positive cable on the battery, the meter makes the connection and immediately starts smoking. If I read that right, it makes sense - the meter is attempting to measure the amp flow from the alternator which is likely way above the 10amp setting on your meter!
Bob that's mostly correct but I'm connecting it between negative strap and negative battery post.

Regarding AMP flow generated by alternator, sorry for not understanding this better but is that even possible if car is not running (alternator is not spinning) or does it some how effect AMP just by being introduced to a circuit?

Thanks!
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 03-13-2013, 02:15 PM
sedanbob's Avatar
Registered User
 
Last photo:
Join Date: Oct 2008
Location: St. Louis
Age: 66
Posts: 626
Wiki Edits: 0

Thanks: 61
Thanked 80 Times in 77 Posts
The flow of amps would be through the entire circuit - negative side included. HOWEVER - I mis-interpreted your original post - when you said the car was stationary, I didn't read that as 'not running'. If there is amp flow in that case, there is a short between the positive connection on the alternator and ground. Sorry I mis-read that.

With the cable disconnected from the alternator, use your meter on the ohms setting to see if you get a zero (or low) ohm reading between the alternator post and a good ground. That will tell you if the short is internal to the alternator.

Sorry for the initial confusion.
Reply With Quote Quick reply to this message
The Following User Says Thank You to sedanbob For This Useful Post:
Aleksey (03-13-2013)
  #7 (permalink)  
Old 03-13-2013, 05:41 PM
EOD Guy's Avatar
Registered User
 
Last photo:
Join Date: Aug 2010
Location: Alabama
Posts: 2,145
Wiki Edits: 0

Thanks: 1
Thanked 156 Times in 144 Posts
The alt housing should be grounded via the monting bolts same with the starter so that has nothing to do with it....... if your main charge wire being hooked up is causing a path to ground..... it's got to the the internal regulator or terminal shorting to ground. If the regulator has fried then the hot wire would give you a massive draw or if the #1 and #2 terminal wires have somehow got swithed then the #1 terminal actualy goes to ground when the alt isn't producing juice (that's why the idiot light lights when the alt isn't spinning and producing juice, it gets it's ground from the internal reg) and the #2 terminal is the sense wire (tells the alt to produce more or less juice depending on the demands of the elec system) and is tied directly to the hot side of the elec system....... if they got switched somehow the hot side of the elec sys would be tied directly to ground when the alt wasn't spinning.

When you hook up the charge wire does the alt housing get hot?....... if so it's shorted to ground....... get it tested (again) if it's good, I'd be suspect of the wiring
Reply With Quote Quick reply to this message
The Following User Says Thank You to EOD Guy For This Useful Post:
Aleksey (03-13-2013)
  #8 (permalink)  
Old 03-13-2013, 06:00 PM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
The alternator is brand new and was tested again once it was put in.

You are right its grounded via engine block that that brings me to this things:

1. Unplug everything from positive lead except that cable, if there is still a short I isolated some other wires touching the engine block.

2. Check if engine block is a good ground

3. Check engine to frame ground strap

4. Check starter ground (which is the engine block too)

Anything I'm missing here? Also if I remove power wire from starter and just let it hang that's good to see if the fault was on that end or should i ground that end?

Thanks.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 03-13-2013, 06:07 PM
T-bucket23's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Engine basic condition - how to check Last photo:
Join Date: Aug 2005
Location: Massachusetts
Age: 57
Posts: 5,362
Wiki Edits: 26

Thanks: 9
Thanked 145 Times in 128 Posts
Pull the positive wire off the alternator, disconnect the battery and check from the positive alternator lead to ground. There should be infinite resistance. Sounds to me like you alternator feed is shorted to ground. Follow the wire from one end to the other.
After re-reading your post, I think you have a ground issue or a bad alternator.
Dont rule out it being bad because it is new.
Also a 10 amp meter is useless on automotive work, you are just going to burn it up.
When the car int running the alternator should not draw anything
__________________
Artificial Intelligence is no match for Natural Stupidity



Chet
Reply With Quote Quick reply to this message
The Following User Says Thank You to T-bucket23 For This Useful Post:
Aleksey (03-13-2013)
  #10 (permalink)  
Old 03-13-2013, 07:25 PM
EOD Guy's Avatar
Registered User
 
Last photo:
Join Date: Aug 2010
Location: Alabama
Posts: 2,145
Wiki Edits: 0

Thanks: 1
Thanked 156 Times in 144 Posts
1. Unplug everything from positive lead except that cable, if there is still a short I isolated some other wires touching the engine block.

Don't think you'll learn anything new (unless I misunderstood your previous posts) ..... because if you disconnect from the alt and the issue goes away, nothing else is shorted beacuse it would show up wheather the alt wire was connected or not.

2. Check if engine block is a good ground

If it didn't have a good ground you wouldn't have a short, you'd have no continuity

3. Check engine to frame ground strap

Same as 2

4. Check starter ground (which is the engine block too)

Same as 2

Don't get me wrong it's always good to check for good grounds...... but a good ground isn't causing your issue....... your issue is you have a hot source going to ground which is draining your battery.

try unbolting the alt and lay it on some insulating material and leave the wires hooked up...... if the issue goes away, it's your alt grounding out internally
Reply With Quote Quick reply to this message
The Following User Says Thank You to EOD Guy For This Useful Post:
Aleksey (03-13-2013)
  #11 (permalink)  
Old 03-13-2013, 07:29 PM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
Thanks.. will try it's a mission to get the alternator out, oh well.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 03-14-2013, 04:43 AM
EOD Guy's Avatar
Registered User
 
Last photo:
Join Date: Aug 2010
Location: Alabama
Posts: 2,145
Wiki Edits: 0

Thanks: 1
Thanked 156 Times in 144 Posts
I've changed alt on Bimmers before....... if you can unbolt it and shove some card board between it and the mounting points..... you're just trying to isolate it from ground.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 03-27-2013, 11:07 PM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
Sooo updates

Hey guys, I been reading up on electricity and been in and out of garage had some progress but still very confused. I don't know if this is normal.

First thing first, I tested ground points (hood strap and engine block to chasis strap) by running positive and negative across both everything was 12V+.

The oil filter that alternator bolts on to reported same, assuming that is a GOOD ground.

Now interesting stuff:

With negative battery strap unplugged I ran continuity test from alternator wire to ground (chasis) and got a reading, meaning + wire that goes to alternator from positive post was mixing with ground.

I unbolted alternator and did it again, no continuity.

Then I unplugged positive wire from alternator and just tested it, no continuity.

So then I touched one of the longer brackets (that /should/ be ground) to oil filter (which is grounded to engine) and got a reading. So to me that looks like alternator is grounding live wire via it's own body to engine.

I assume this is NOT normal? But here is what's confusing:
  1. Alternator unplugged on the ground, continity test using positive to live wire connector and negative to alternator's bracket that should be ground I had no reading
  2. But when I switched negative to positive connection and positive to the bracket I got redicilous number like 123002

Any ideas what to do now? I also checked if maybe I'm shorting out at engine block level because its not reaching the ground but it detected flow from oil filter (which should be ground for alternator) all the way to the hood (ground post).
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 04-04-2013, 01:35 PM
Aleksey's Avatar
Founder @ Maintenr
 
Last photo:
Join Date: Dec 2012
Location: New York
Posts: 28
Wiki Edits: 0

Thanks: 16
Thanked 1 Time in 1 Post
Thanks for all the help guys, problem has been solved.

Due to new design if BMW's power steering hoses they no longer bend outwards as original ones so the whole issue was caused by the steering hose I replaced while rebuilding front end.

The BOSCH alternator has really long thread (about 1 inch exposed after you tighten the nut) so once alternator is 100% in and secured the thread combined with new design of the hose would touch it slightly causing positive cable to be grounded.

I simply dremeled the remaining thread off to avoid them touching.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 04-04-2013, 05:15 PM
EOD Guy's Avatar
Registered User
 
Last photo:
Join Date: Aug 2010
Location: Alabama
Posts: 2,145
Wiki Edits: 0

Thanks: 1
Thanked 156 Times in 144 Posts
Good to hear it was a cheap fix......lol
Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last 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.
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 post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Negative caster. Why? south65ss Suspension - Brakes - Steering 1 02-22-2009 08:08 AM
negative camber question jasrking Suspension - Brakes - Steering 1 08-21-2008 11:12 PM
ZZ-4 Negative ?? solidaxel Engine 7 11-25-2007 11:42 PM
Why the negative cable? daimon1054 Electrical 20 08-04-2004 07:18 AM
Volt meter jumps and show negative Lewissr Electrical 8 11-20-2002 03:01 PM


All times are GMT -6. The time now is 11:50 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.