Results 1 to 8 of 8

Thread: Alternator wiring. HELP! Truck won't shut off

  1. #1
    Senior Member Ohio 4x4 Member
    Sr. Forum Member
    SHAKEnBLAKE's Avatar
    Join Date
    Jan 2008
    Location
    Columbus
    Posts
    1,067
    Rep Power
    11

    Alternator wiring. HELP! Truck won't shut off

    Any and all help is appreciated. Please keep in mind that my knowledge of alternators and all things electrical is pretty limited.

    So I had Baby Ram (1996 Dakota with a 1979 318 V8 swap, with a GM alternator and an electric fan) at the mechanic (not Lambert, big mistake). Of course the day that I go to pick it up it starts acting up and won't start. This was the first time there were any issues getting it started. A little bit of backyard mechanic trouble shooting led him to suspect a short or other issue with one of the alternator wires, so he ended up cutting one of the wires and connecting it to the alternator ground (See pic #1: cut wire, connected with yellow terminal to the alternator ground wire)

    Figure 1IMG_6196.jpg

    This allowed the truck to start and run, but now it won't turn off with the ignition, so we had to stall the truck to turn it off. Neither of us had time to mess with it, so I took the truck home as is. Now the voltage gauge stays on, even when the ignition is off, which I THINK is a new feature. It seems that this now drains the battery. Remember, I have limited automotive electrical knowledge. See pic of gauge, showing voltage even with a drained battery and ignition off.

    IMG_6195.jpg

    I tried to trace the wire through the "wiring harness" and got to this mess that I really didn't want to pull apart.

    IMG_6201.jpg

    Here's a pic of the relays and fuses. Notice that there's a 10amp fuse in the 5amp "ign off draw" position. Could this be related to the issue?

    IMG_6200.jpg

    Here's some other pics for reference.

    IMG_6197.jpg

    IMG_6198.jpg
    IMG_5807.jpg

    So my ultimate question is how do I fix this? Is this considered a 2-wire alternator? What's that wire supposed to be connected to? Is this backyard mechanic fix the reason the voltage gauge staying on, or is that normal?

    Some brief googling suggested this might have something to do with the electrical fan, or the horn relay (horn doesn't work, never has). Thoughts?

    Googling also brought up installing a diode. Or a "dummy light." As far as I have noticed, there is no current dash light or dummy light related to the alternator.

    Again, any help is greatly appreciated! Let me know your thoughts!
    Last edited by SHAKEnBLAKE; 11-11-2017 at 06:22 PM.
    -Joe
    1996 Dakota 318



  2. #2
    Member Ohio 4x4 Member
    Forum Member
    LAR-308's Avatar
    Join Date
    Mar 2012
    Location
    Newark
    Posts
    296
    Rep Power
    6
    Did you mean to say the BAT terminal on the alternator is grounded? The BAT terminal should connect to the battery either directly or indirectly. I'll try to help, the wire that jumps to the BAT terminal is good. The other wire isn't needed, It normally feeds the charging light on the cluster of a GM vehicle. Unplug the second wire. If you want a plastic connector, they're available from napa, P/N ECH VRC148. I don't know about the fan, but I can explain how to wire it up if you need, Ron
    1990 YJ, 350 sbc, AX15/231, Tom Woods SYE & shaft, Dana 44's F&R, 5.13's, detroit lockers, 3.5" springs, 1"bl, 1/2" boom shackles, 35" MTR's, Warn 8274, overland bound member #3644

  3. #3
    Senior Member Ohio 4x4 Member
    Sr. Forum Member
    SHAKEnBLAKE's Avatar
    Join Date
    Jan 2008
    Location
    Columbus
    Posts
    1,067
    Rep Power
    11
    I thought that the BAT wire was considered a ground, so that's what I was calling it. But yes, the BAT terminal goes directly to the battery. The wire that jumps to the BAT terminal is the one that we recently changed, which seems to have started the "run-on" problem.
    -Joe
    1996 Dakota 318



  4. #4
    Member Ohio 4x4 Member
    Forum Member
    LAR-308's Avatar
    Join Date
    Mar 2012
    Location
    Newark
    Posts
    296
    Rep Power
    6
    Ok, the jumper wire is pretty much standard, 4 of my vehicles are wired this way. I'd check to see how many wires attach to the ignition coil, the ignition switch cuts power to the coil to shut off the truck. There should be one wire connected to the positive side of the coil. I assume the truck ran normal at some point, what's been done between then and now? Ron
    1990 YJ, 350 sbc, AX15/231, Tom Woods SYE & shaft, Dana 44's F&R, 5.13's, detroit lockers, 3.5" springs, 1"bl, 1/2" boom shackles, 35" MTR's, Warn 8274, overland bound member #3644

  5. #5
    Senior Member Ohio 4x4 Member
    Sr. Forum Member
    SHAKEnBLAKE's Avatar
    Join Date
    Jan 2008
    Location
    Columbus
    Posts
    1,067
    Rep Power
    11
    As far as I know, nothing has been changed other than that jumper wire. My mechanic built a new alternator bracket when he had it, but didn't make any other changes that I know of, unless he accidentally switched those two wires to the alternator. I plan to toy around with it the afternoon. I'll let you know if there are any updates.

    Yesterday I charged the battery, disconnected the second wire, and fired it up. The voltage meter still shows power even with truck off. The truck ran for a minute and then died, I assume because the battery isn't charging at this point. The mechanic expressed suspicion that the alternator was going bad, although the PO had suggested it was pretty new (a refurbished one, though). Would a bad alternator somehow cause the run-on issue?
    -Joe
    1996 Dakota 318



  6. #6
    Member Ohio 4x4 Member
    Forum Member
    LAR-308's Avatar
    Join Date
    Mar 2012
    Location
    Newark
    Posts
    296
    Rep Power
    6
    Normally an alternator won't cause a vehicle to run after the ignition switch is off. The power to the ignition switch comes from the ignition switch. How many wires on the positive side of the ignition coil?
    1990 YJ, 350 sbc, AX15/231, Tom Woods SYE & shaft, Dana 44's F&R, 5.13's, detroit lockers, 3.5" springs, 1"bl, 1/2" boom shackles, 35" MTR's, Warn 8274, overland bound member #3644

  7. #7
    Moderator / Life Member Moderator
    Sr. Forum Member

    Join Date
    May 2003
    Posts
    3,523
    Rep Power
    2118
    Assuming truck ran fine prior to going to mechanic, he "built a new alternator bracket", truck will not start so he rigs up some wire and now it's messed up....so yes, I would say something was changed. If he built a new alternator bracket than you have to assume he removed the alternator and the wiring when doing this, so my first suspicion he either connected the wiring wrong or a wire or connector was damaged when it was reinstalled. I would not be assuming this is some brand new problem but rather related to something done by the mechanic.
    Brad
    '90 Blazer - 6.2 diesel, 700r4, Dana 60, 14 bolt, locked, 39.5" Super Swamper TSLs, winch, rollcage, yada, yada, yada......

  8. #8
    Member Ohio 4x4 Member
    Forum Member
    LAR-308's Avatar
    Join Date
    Mar 2012
    Location
    Newark
    Posts
    296
    Rep Power
    6
    I'm not assuming there is a new problem, If he can narrow down which circuit is back feeding, keeping the engine running it may lead to the mechanics issue, ROn
    1990 YJ, 350 sbc, AX15/231, Tom Woods SYE & shaft, Dana 44's F&R, 5.13's, detroit lockers, 3.5" springs, 1"bl, 1/2" boom shackles, 35" MTR's, Warn 8274, overland bound member #3644

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Two Batteries vs. High Amp Alternator
    By Roy in forum Upgrades
    Replies: 16
    Last Post: 11-20-2009, 03:50 PM
  2. Alternator quits on way home from Picnic
    By SES in forum Mechanic's Corner
    Replies: 4
    Last Post: 04-28-2008, 01:01 PM
  3. Alternator
    By Evan in forum Upgrades
    Replies: 5
    Last Post: 07-11-2007, 08:56 AM
  4. Powermaster 100 Amp Alternator
    By Blazing72 in forum For Sale
    Replies: 0
    Last Post: 09-15-2006, 12:07 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •