Dead Battery caused by alternator? - Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum
Ford Focus Forum
HomeContact UsAbout UsGalleryDiscussion ForumsMarketplace


Go Back   Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum > Ford Focus Tech Discussions > General Technical Chat

General Technical Chat This section is for technical discussions relating to general maintenance, electrical issues, engine trouble, and recalls.

Search This Forum | Image Search | Advanced Search    
Ford Focus Tire & Wheels FocusFanatics Merchandise

Reply
 
Thread Tools Display Modes
Old 06-14-2008, 04:10 PM   #1
fireboy2
Focus Rookie
 
Join Date: Jun 2008
Fan#: 56864
Location: uk
What I Drive: 2001 tddi ghia

Posts: 5
FF Reputation: 1 fireboy2 Good Standing Member
Buy-Sell-Trade Rating: (0)
Dead Battery caused by alternator?

Hi there all, I tried to start my car after leaving it for a day but the battery was totally dead. I thought it was just time for a new battery but when I fitted a shiny new one it was flat the morning after. I have done some checks with my multimeter and found the following. When running the battery charges up to about 14.4v as it should but when not running the battery voltage slowly drops. It drops a few millivolts every couple of minutes. If you disconnect the large positive cable that runs to the alternator it doesnt drop at all. The cable has a resistance of about 30k ohms to earth. Any ideas. Oh Ps the alternator was changed in December and it's a 2001 tddi ghia. Any help would be really appriciated ta.


fireboy2 is offline  
    Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 06-14-2008, 05:11 PM   #2
ShamrockSVT
Focus Enthusiast
 
ShamrockSVT's Avatar
 
Join Date: Jun 2007
Fan#: 47719
Location: Glendale, AZ
What I Drive: 2011 Ford Fiesta SE

Posts: 3,002
FF Reputation: 72 ShamrockSVT Excellent Standing Member
Buy-Sell-Trade Rating: (1)
Sounds like you may have a draw somewhere in the system, but its not the Alt, which simply can't consume electricity
__________________
ShamrockSVT: Doing my part
ShamrockSVT is offline  
    Reply With Quote Quick reply to this message
Old 06-14-2008, 09:20 PM   #3
oddballish
Focus Enthusiast
 
Join Date: Oct 2007
Fan#: 51285
Location: washougal Wa.
What I Drive: 2006,Blue,fx4

Posts: 92
FF Reputation: 1 oddballish Good Standing Member
Buy-Sell-Trade Rating: (0)
Shamrock it is possible to have an Alt short internally and bleed back though it is extremely uncommon. The quickest way to check is to loosen the out-put nut on the stud and in a dark shop (I know where the Alt is located its dark already) wiggle the wire and look for a spark, no spark no bleed back
oddballish is offline  
    Reply With Quote Quick reply to this message
Old 06-14-2008, 09:46 PM   #4
fireboy2
Focus Rookie
 
Join Date: Jun 2008
Fan#: 56864
Location: uk
What I Drive: 2001 tddi ghia

Posts: 5
FF Reputation: 1 fireboy2 Good Standing Member
Buy-Sell-Trade Rating: (0)
I have already disconnected the cable from the output stud on the alternator and the fault disappers so it does look like the alternator is comsuming electricity but I need to know how the alternator is wired up inside before I can diagnose the fault anymore. Does anyone have a wiring diagram or can anyone explain it to me?
fireboy2 is offline  
    Reply With Quote Quick reply to this message
Old 06-14-2008, 09:53 PM   #5
Blurvfocus
Focus Fanatic
 
Blurvfocus's Avatar
 
Join Date: Nov 2004
Fan#: 15299
Location: Temple, PA
What I Drive: 03 ZX3 Wine Cooled Eng.

Posts: 2,199
FF Reputation: 54 Blurvfocus Excellent Standing Member
Buy-Sell-Trade Rating: (1)
Yeah, if it's a big draw, it probably is the alternator.

Disconnect the fat red wire at the alternator, There should be no sparking at that post whatsoever. Then let this thing sit overnight and see if the battery stays up.

Shamrock- the alternator has diodes in it that allow current to pass in one direction (out). There's three of them in there, but if one goes bad, it'll allow current to flow in either direction. When that happens, the alternator will still function, but when the car isn't running, it'll just sit there and draw current through it's coils.
__________________
Often wrong but never in doubt.
Blurvfocus is offline  
    Reply With Quote Quick reply to this message
Old 06-14-2008, 09:54 PM   #6
oddballish
Focus Enthusiast
 
Join Date: Oct 2007
Fan#: 51285
Location: washougal Wa.
What I Drive: 2006,Blue,fx4

Posts: 92
FF Reputation: 1 oddballish Good Standing Member
Buy-Sell-Trade Rating: (0)
Get an old test light, not an LED, clip to the out put stud and touch the wire you disconnected .If the light comes on you have a short,
oddballish is offline  
    Reply With Quote Quick reply to this message
Old 06-14-2008, 10:01 PM   #7
Blurvfocus
Focus Fanatic
 
Blurvfocus's Avatar
 
Join Date: Nov 2004
Fan#: 15299
Location: Temple, PA
What I Drive: 03 ZX3 Wine Cooled Eng.

Posts: 2,199
FF Reputation: 54 Blurvfocus Excellent Standing Member
Buy-Sell-Trade Rating: (1)
Do you want to fix the alternator yourself? I'm not sure about this alternator specifically, but the diodes are usually pressed into a plate. You can replace them if you have a vise and a couple of sockets, or they might be sold as a diode trio assembly, already pressed into a plate.

Don't worry about "how it's wired up inside". When you get apart you'll see that it pretty much goes back together only one way. If in doubt, and if you have a digital camera, take lots of pictures as you take it apart.
__________________
Often wrong but never in doubt.
Blurvfocus is offline  
    Reply With Quote Quick reply to this message
Old 06-14-2008, 10:41 PM   #8
fireboy2
Focus Rookie
 
Join Date: Jun 2008
Fan#: 56864
Location: uk
What I Drive: 2001 tddi ghia

Posts: 5
FF Reputation: 1 fireboy2 Good Standing Member
Buy-Sell-Trade Rating: (0)
Blurvfocus, I think you hit the nail on the head with a blown diode within the alternator. I'll try taking the alt off tomorrow and see if I can find the offending item. Cheers for the assistance everyone.
fireboy2 is offline  
    Reply With Quote Quick reply to this message
Old 06-18-2008, 02:48 PM   #9
fireboy2
Focus Rookie
 
Join Date: Jun 2008
Fan#: 56864
Location: uk
What I Drive: 2001 tddi ghia

Posts: 5
FF Reputation: 1 fireboy2 Good Standing Member
Buy-Sell-Trade Rating: (0)
just to let you know I changed the alternator yesterday and everything is now fine. I even managed to get the alternatorfor free as it was still under a 12 month warranty from last time it was changed for not charging the battery. Cheers for all the help again guys.
fireboy2 is offline  
    Reply With Quote Quick reply to this message
Reply

Bookmarks & Social Networks

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum 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.
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
Display Modes

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery or alternator? focusmmuter General Technical Chat 5 05-26-2007 02:55 PM
Dead Alternator, Dead Battery Atlanta800 Car Audio, SYNC, MyFord Touch & Electronics 19 07-02-2006 05:13 AM
Dead Alternator, which to get and where to get it? Portuga General Technical Chat 3 01-20-2006 06:04 AM
alternator to battery cable? pio Ford Focus & General Car Chat 0 11-25-2003 11:10 AM


All times are GMT -5. The time now is 05:30 PM.


Copyright 2002-2014 FocusFanatics.com. All Rights Reserved : Privacy Policy : Advertise Information

Focus Fanatics Ford Focus Forum offers many fun ways for you to engage with other Ford Focus Owners from across the world. Whether it be about the aftermarket performance modifications, technical how-to's, European tuned suspension or awesome fuel economy similar to the Audi S3, Ford Fusion and Acura TLX. You can find all Ford Focus and Focus ST related information here. Join our Ford Focus discussion forums and chat with local Focus enthusiasts in your area. Challenger Hellcat - Charger Hellcat