Notices
1994.5 - 1997 7.3L Power Stroke Diesel  

phantom battery draw

Thread Tools
 
Search this Thread
 
Old Aug 29, 2019 | 12:22 PM
  #1  
robert kelsey's Avatar
robert kelsey
Thread Starter
|
Mountain Pass
20 Year Member
Liked
Joined: Aug 2003
Posts: 101
Likes: 1
From: california
Question phantom battery draw

Can a bad alternator create a phantom draw down on batteries when not running,
Yet still fully charge them once it's running ??
 
Reply
Old Aug 29, 2019 | 02:54 PM
  #2  
powermax's Avatar
powermax
New User
Joined: Jun 2009
Posts: 2
Likes: 0
From: South Western Oregon
Phantom Draw

I am pretty sure it can.

A bad Diode can do that.

I would connect a volt meter between positive battery cable and the battery to see if there is a draw then disconnect alternator and see if draw goes away.
 
Reply
Old Aug 29, 2019 | 03:27 PM
  #3  
knottyrope's Avatar
knottyrope
Lead Driver
10 Year Member
Photogenic
Shutterbug
Loved
Joined: Apr 2016
Posts: 7,177
Likes: 1,335
From: Bahstun
These alts have been known to do this
There are 6 diodes in most alts. only takes one to short out and do this
If not the alt, then its time to pull fuses till you find the circuit making the high draw
 
Reply
Old Aug 29, 2019 | 03:30 PM
  #4  
seville009's Avatar
seville009
Logistics Pro
Joined: Nov 2004
Posts: 4,795
Likes: 47
I had a skidsteer alternator that would draw down the battery when it was not running. Probably the same general principle applies the auto alternators and batteries
 
Reply
Old Aug 29, 2019 | 06:51 PM
  #5  
Hit Man X's Avatar
Hit Man X
Lead Driver
20 Year Member
Liked
Loved
Community Favorite
Joined: Sep 2002
Posts: 9,492
Likes: 2,019
From: North Texas
Fixed alt draw on a '76 IH Scout. Bad regulator on it actually, but I agree w everyone else...start with a draw test and go from there.

Easy easy.
 
Reply
Old Aug 30, 2019 | 11:01 AM
  #6  
knottyrope's Avatar
knottyrope
Lead Driver
10 Year Member
Photogenic
Shutterbug
Loved
Joined: Apr 2016
Posts: 7,177
Likes: 1,335
From: Bahstun
remove both battery negative terminals
when removing last one pay attention to the sparks it makes


remove alt big thick wire and tape up
put on one neg to battery and see if it sparks as much as before, if it don't then alt is bad
 
Reply
Old Aug 30, 2019 | 02:46 PM
  #7  
tjc transport's Avatar
tjc transport
i ain't rite
Joined: Mar 2005
Posts: 65,443
Likes: 5,516
From: Marlboro Mental Hospital.
Club FTE Gold Member
i find the easiest way to tell a bad diode in the alternator is to feel it after the engine cools off. if the alternator is warm, or hot, there is a bad diode in it causing the parasitic draw.
 
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
teppler
6.0L Power Stroke Diesel
10
Aug 19, 2020 09:55 PM
johnarla
1997 - 2006 Expedition & Navigator
5
Mar 28, 2013 11:18 AM
crestfallinman
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
33
Mar 1, 2012 09:54 AM
300workhorse
1973 - 1979 F-100 & Larger F-Series Trucks
6
Oct 6, 2009 05:06 PM
CowDawg
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
2
Feb 17, 2000 10:14 AM




All times are GMT -5. The time now is 12:08 AM.

story-0
Top 10 Ford Truck Tragedies

Slideshow: Top 10 Ford truck tragedies.

By Joe Kucinski | 2026-05-18 19:34:33


VIEW MORE
story-1
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make

And it might be even better than that.

By Brett Foote | 2026-05-18 19:26:42


VIEW MORE
story-2
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!

Slideshow: Does lowering an F-150 Lobo RUIN the ride quality?

By Michael S. Palmer | 2026-05-18 19:20:37


VIEW MORE
story-3
Ford's 2001 Explorer Sportsman Concept Looks For a New Home

Slideshow: Ford's bizarre fishing-themed Explorer concept has resurfaced after spending decades largely forgotten.

By Verdad Gallardo | 2026-05-12 18:07:46


VIEW MORE
story-4
10 Best Ford Truck Engines We Miss the Most!

Slideshow: The 10 best Ford truck engines we miss the most.

By Joe Kucinski | 2026-05-12 13:09:47


VIEW MORE
story-5
2026 Shelby F-150 Off-Road: Better Than a Raptor R?

Slideshow: first look at the 810 hp 2026 Shelby F-150 Off-Road!

By Brett Foote | 2026-05-12 12:50:07


VIEW MORE
story-6
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!

Slideshow: Everything You Need to Know about the 2027 Super Duty Carhartt Package!

By Michael S. Palmer | 2026-05-07 17:51:06


VIEW MORE
story-7
10 Most Surprising 2026 Ford Truck Features!

Slideshow: 10 most surprising Ford truck options/features in 2026.

By Joe Kucinski | 2026-05-05 11:17:22


VIEW MORE
story-8
Top 10 Ford Trucks Coming to Mecum Indy 2026

Slideshow: Here are the top 10 Fords coming to Mecum Indy 2026.

By Brett Foote | 2026-05-04 13:49:49


VIEW MORE
story-9
5 Best / 5 Worst Ford Truck Wheels of All Time

Slideshow: The 5 best and 5 worst Ford truck wheels of all time

By Joe Kucinski | 2026-04-29 16:49:01


VIEW MORE