Service Charging System, Battery Not Charging - P1638 Code
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 7 of 7
Electrical Technical Information Discussion, Service Charging System, Battery Not Charging - P1638 Code in Item Specific Cadillac Discussion; I have a 98 STS and was having overheating issues with my car this past week. My husband narrowed it ...
  1. #1
    tfrost is offline Cadillac Owners Member
    Automobile(s): 2005 STS V-8
    Join Date
    Jan 2004
    Posts
    4

    Service Charging System, Battery Not Charging - P1638 Code

    I have a 98 STS and was having overheating issues with my car this past week. My husband narrowed it down to the waterpump and replaced it. When replacing the waterpump he cracked the waterpump housing and had to replace that. He also decided to replace the fuel rail while he was at it.
    Everthing is back together, but nows there's a different problem, when starting it a meesage appears on the dash that says "Service Charging System, Battery Not Charging" and will die after a minute. I ran the codes and get a P1638 (Generator F-Terminal Circuit). What exactly does this mean? I did not have this problem before he did the waterpump, waterpump housing and fuel rail work. Could he have damaged something and not realized it? Where does he start to find it?

    My husband is pretty good when it comes to working on cars but this is his first crack on my Cadillac and he is fed up and says next time I have a problem I will take it to a dealer.

    Any suggestions would be great
    Theresa

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    Leeb's Avatar
    Leeb is offline Cadillac Owners Enthusiast
    Automobile(s): did this once... 86 Deville, 86 300E, 78 R100rs
    Join Date
    Jun 2005
    Location
    Palm Spgs CA
    Age
    54
    Posts
    517

    Re: Service Charging System, Battery Not Charging - P1638 Code

    He removed the alternator to do all of this work, yes?
    Sounds like he didn't get the multi-pin connector plugged back in, or not quite...
    Possibly damaged those wires... but more likely it didn't get plugged in well...

    There aren't that many connections to make. That one, and the large wire to the battery that connects to the post on back... unless they made MAJOR changes to the design... that should be it.

    Done that exact same thing myself... then hit my head on the hood latch.
    Painful, but justified...

  4. #3
    tfrost is offline Cadillac Owners Member
    Automobile(s): 2005 STS V-8
    Join Date
    Jan 2004
    Posts
    4

    Re: Service Charging System, Battery Not Charging - P1638 Code

    The alternator was never removed to do this work.
    After he performed the work I mentioned a code came up that read P1638 which is the Generator F-Terminal Circuit. We are wondering what this could be especially when the alternator was never touched during this whole process.

  5. #4
    Leeb's Avatar
    Leeb is offline Cadillac Owners Enthusiast
    Automobile(s): did this once... 86 Deville, 86 300E, 78 R100rs
    Join Date
    Jun 2005
    Location
    Palm Spgs CA
    Age
    54
    Posts
    517

    Re: Service Charging System, Battery Not Charging - P1638 Code

    Then it sounds as if either...
    1) the wiring to the alternator has been damaged (it still could have been loosened by the other work), or
    2) the internal regulator has failed for whatever reason.

    But just to be sure,
    check ALL the fuses to ensure NOTHING is 'bad'. More than likely tho,
    it is 1) or 2)...

    Alternators are pretty straightforward devices these days... very self-contained.

    Hope this helps!

  6. #5
    osh
    osh is offline Cadillac Owners Member
    Join Date
    Mar 2013
    Posts
    1

    Re: Service Charging System, Battery Not Charging - P1638 Code

    what is the Generator F-Terminal Circuit? ive tested the battery and it good and the alt is good to. ive checked all the connection and wires and all are good as well. even the fuses are good. but still getting battery not charging & service charging system on the dash with the p1638 code... im confused on what to look for now. any ideas?
    thnaks

  7. #6
    raisancaddy is offline Cadillac Owners Member
    Automobile(s): 1987 seville
    Join Date
    Nov 2013
    Age
    56
    Posts
    3

    Re: Service Charging System, Battery Not Charging - P1638 Code

    having the same problem on a 87 seville 4.1b all of the sudden not charging . replaced with used altenator same issue , weird

  8. #7
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    45,011

    Re: Service Charging System, Battery Not Charging - P1638 Code

    Old thread, but - The F terminal (Field) receives system (battery, at start) voltage to excite the windings and voltage regulator. No F voltage, no charge. The L terminal (Light, for the old idiot light) now sets the warning message - same idea - no alternator excitation, no charge indication.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

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.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting