Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

ej25 from 1999 Forester - 3 pin alternator wiring question


  • Please log in to reply
14 replies to this topic

#1 JasonPap2002

JasonPap2002

    New User

  • Members
  • Pip
  • 8 posts
  • Austin, Texas

Posted 05 September 2013 - 08:42 PM

Hi Folks,

 

I have an ej25 alternator wiring question that you may be able to help with.  Essentially my alternator warning lamp is not receiving ground from pin one in the 3 pin connector shown here:

 

Attached File  connector.jpg   4.33K   37 downloads

 

Wiring in my car is here:

 

Attached File  photo.JPG   41.28K   17 downloads

 

I can make the alternator warning lamp turn on when I touch the wire going to pin 1 (L) to ground.  My pin 2 (S) is receiving 13 volts (going to B+).

 

Try as I can it seems that pin 1 is open.  However if 12 volts is not on it when started the alternator only puts out 13 volts.  When 12 volts is on it (from the alternator warning lamp wire) then fields excite and it bumps to 15 volts.

 

Any ideas?  I'm beginning to think it's an internal issue - not much else that it can be!  Alternator seems to work fine otherwise...

 

Thanks folks!

 

~Jason

 

 



#2 Cougar

Cougar

    Elite Master of the Subaru

  • Members
  • 6,342 posts
  • Anchorage

Posted 05 September 2013 - 10:15 PM

Well it seems you have proved the wiring to pin 1 is okay. Manually grounding that wire should turn on the warning light. When the alternator isn't running and the ignition is on then pin 1 should be at ground potential through the alternator circuit and the warning light turned on. It appears that isn't happening so check the voltage on pin 1 with things connected normally and see if you see voltage there. You most likely will since the warning light isn't turning on and something inside the alternator isn't right.



#3 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 9,085 posts
  • Charlottesburg, VA

Posted 06 September 2013 - 12:39 AM

So the light works, but it doesn't turn on during the bulb test?

#4 JasonPap2002

JasonPap2002

    New User

  • Members
  • Pip
  • 8 posts
  • Austin, Texas

Posted 06 September 2013 - 08:25 AM

Well it seems you have proved the wiring to pin 1 is okay. Manually grounding that wire should turn on the warning light. When the alternator isn't running and the ignition is on then pin 1 should be at ground potential through the alternator circuit and the warning light turned on. It appears that isn't happening so check the voltage on pin 1 with things connected normally and see if you see voltage there. You most likely will since the warning light isn't turning on and something inside the alternator isn't right.

Cool - I just checked and found that on pin 1 with ignition on I get 5-6 volts.  It must be coming in through B+ terminal because no other wires are connected.  

 

Otherwise it appears the alternator is working fine - putting out 15 volts or more when all wires are connected.  But I really want that alternator light to work!  (I'm OCD sometimes).

 

Anyone know if it's worth opening up and taking a look inside the alt?  Or perhaps I'm missing something else?

 

Pin 1 is the pin closest to B+ terminal, correct?  Grasping at straws here.  :-)


Thanks in advance!



#5 JasonPap2002

JasonPap2002

    New User

  • Members
  • Pip
  • 8 posts
  • Austin, Texas

Posted 06 September 2013 - 08:26 AM

So the light works, but it doesn't turn on during the bulb test?

I think by bulb test you mean touching the alternator warning lamp wire to ground directly (instead of pin 1), and yes it works then...  Really weird issue but slowly pointing to internal alternator issues...

 

~Jason



#6 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 9,085 posts
  • Charlottesburg, VA

Posted 06 September 2013 - 10:21 AM

Bulb test is when all of the warning lights in the dash turn on when you turn the key to ON. Cel, AT Temp, battery, oil pressure, seatbelt, etc. Some turn on then turn back off after a few seconds. Others the engine has to start before they will turn off.

The battery light comes on during the bulb test, then turns off after the engine starts. (If this is how the bulb behaves, the circiut is working normally)

If the alternator is not spinning the pin acts as a ground path for the bulb circuit (power flows from fuse box to bulb to alternator to ground). Once spinning, the alternator supplies a matching voltage to the pin which prevents current flow, so the bulb does not light. (Power from fuse box, power from alternator, meet in the middle at the bulb, neither can pass the other, no current flow means bulb is not lit, power struggle ensues, neither has an advantage. Eventually alternator gives up and stops charging after many tens or hundreds of thousands of miles, light turns on)

#7 Olnick

Olnick

    Ol' Subaru Guy

  • Members
  • 2,646 posts
  • Honolulu HI

Posted 06 September 2013 - 01:35 PM

Great explanation Fairtax!  I never knew how that worked.  Thanks.



#8 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 9,085 posts
  • Charlottesburg, VA

Posted 06 September 2013 - 02:24 PM

I learned that from one of Cougar's posts on here quite a while ago. :)

#9 JasonPap2002

JasonPap2002

    New User

  • Members
  • Pip
  • 8 posts
  • Austin, Texas

Posted 06 September 2013 - 04:57 PM

Bulb test is when all of the warning lights in the dash turn on when you turn the key to ON. Cel, AT Temp, battery, oil pressure, seatbelt, etc. Some turn on then turn back off after a few seconds. Others the engine has to start before they will turn off.

The battery light comes on during the bulb test, then turns off after the engine starts. (If this is how the bulb behaves, the circiut is working normally)

If the alternator is not spinning the pin acts as a ground path for the bulb circuit (power flows from fuse box to bulb to alternator to ground). Once spinning, the alternator supplies a matching voltage to the pin which prevents current flow, so the bulb does not light. (Power from fuse box, power from alternator, meet in the middle at the bulb, neither can pass the other, no current flow means bulb is not lit, power struggle ensues, neither has an advantage. Eventually alternator gives up and stops charging after many tens or hundreds of thousands of miles, light turns on)

Thanks for this!  In this case, bulb test is NOT working then.  I get no alternator lamp on when turning the ignition on.

 

I feel that the internals of the alternator are not providing a path to ground when i turn on the ignition.  Its an open circuit and so remains unlit.

 

Anyone know if there is anything inside easily replaceable for this?  Or ?

 

I appreciate all the insight!

 

~Jason



#10 naru

naru

    1000+ Super USER!

  • Members
  • 1,828 posts
  • under the bridge

Posted 06 September 2013 - 05:28 PM

Thanks for this!  In this case, bulb test is NOT working then.  I get no alternator lamp on when turning the ignition on.

 

I feel that the internals of the alternator are not providing a path to ground when i turn on the ignition.  Its an open circuit and so remains unlit.

 

Anyone know if there is anything inside easily replaceable for this?  Or ?

 

I appreciate all the insight!

 

~Jason

 

I`ve had bad brushs cause the bulb test to fail on other makes.



#11 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 9,085 posts
  • Charlottesburg, VA

Posted 06 September 2013 - 11:20 PM

The grounding circuitry for the bulb is built into the voltage regulator.
FSM suggests one of the diodes in the regulator could be bad, but its probably not repairable.

The circuit is grounded to the case of the alternator, so it may be worh a shot to ensure that the case is well grounded to the mounting bracket.

#12 JasonPap2002

JasonPap2002

    New User

  • Members
  • Pip
  • 8 posts
  • Austin, Texas

Posted 07 September 2013 - 05:08 PM

The grounding circuitry for the bulb is built into the voltage regulator.
FSM suggests one of the diodes in the regulator could be bad, but its probably not repairable.

The circuit is grounded to the case of the alternator, so it may be worh a shot to ensure that the case is well grounded to the mounting bracket.

 

Thanks!  I tried pushing a grounded wire to the outside of the case but will give a go with wiring it in a bit more solidly.  I have a feeling it's the voltage regulator if this doesn't work.  

 

I hate to put a new alt in there, but what can you do.

 

Thanks again folks!  Any one of you in Austin some time, a beer on me.


~Jason



#13 Cougar

Cougar

    Elite Master of the Subaru

  • Members
  • 6,342 posts
  • Anchorage

Posted 07 September 2013 - 05:45 PM

The alternator case is grounded to the engine so touching another ground to it isn't going do anything. If the alternator is fairly old then fixing just this problem is just basically a bandaid as it most likely needs a whole rebuild. Get yourself a good rebuilt or used replacement unit. That's my advice anyways. It is a lot easier than trying to repair it. Either way the unit has to be removed from the car. Be sure to remove the battery ground wire first before working on the alternator. The main alternator wire is hot to the battery and sparks will fly if it gets shorted to ground with the battery connected.



#14 JasonPap2002

JasonPap2002

    New User

  • Members
  • Pip
  • 8 posts
  • Austin, Texas

Posted 07 September 2013 - 10:42 PM

The alternator case is grounded to the engine so touching another ground to it isn't going do anything. If the alternator is fairly old then fixing just this problem is just basically a bandaid as it most likely needs a whole rebuild. Get yourself a good rebuilt or used replacement unit. That's my advice anyways. It is a lot easier than trying to repair it. Either way the unit has to be removed from the car. Be sure to remove the battery ground wire first before working on the alternator. The main alternator wire is hot to the battery and sparks will fly if it gets shorted to ground with the battery connected.

 

Good tips!  Yes I agree that a new/used/rebuilt one is where I should go with this.  I do appreciate all of your advice, it's been very helpful.


~Jason



#15 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 9,085 posts
  • Charlottesburg, VA

Posted 09 September 2013 - 06:01 PM

Last time I checked prices for one of these Subaru wanted close to $500 for a reman. The after market places wanted $275-400.
Cheap fix: grab a two wire plug and from a 95-98 and splice that in. The wire for the light is the same, the other two just end up in the fuse box (they may have even joined before getting there IIRC).
Then you can buy the $75 Subaru Reman alternator for the 95-98 Legacy.

Bolts right in, works great. Did this on a friends 99 foz a few years ago and its still chugging along just peachy. (And she was thrilled that I saved her almost $400)




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users