Installing '10 GT alternator in '06 GT: How to connect? Please help

Discussion in '2005+ Mustang GT 4.6L Tech' started by Stangabe, Jan 13, 2021.

  1. Stangabe

    Stangabe Junior Member

    WOWW!! Applying heat with a hair dryer totally worked!! :signs1: I didn't have to remove the pulley in the end. Thank you guys so much!! This forum is awesome.

    Going to install it in a couple hours. Wish me luck
  2. AndrewNagle

    AndrewNagle forum member

    good luck
    Stangabe likes this.
  3. Stangabe

    Stangabe Junior Member

    Hey guys, I'm not sure if I should open another thread for this, but things didn't exactly turn out as planned. Please, would highly appreciate your advice on the following:

    I managed to just squeeze it in there after clocking the alt as you guys suggested. I also had to cut down the long ass + stud on the alternator to keep it from hitting the metal coolant pipe and made sure to wrap the rubber cap of the O-ring and the PCM connection in electrical tape to stop them from possibly rubbing or shorting out against the pipe. Did have to guide the wires of PCM plug at an awkward 90 degree angle up against the coolant pipe (which may have kinked it?). Put it back together and started the engine. Idled it for 15 minutes, no crazy dash lights or 'check charging system'. Did some revs, engine seemed to run great at least.

    So I took it out to my mechanic down the road the morning after to have my work checked. Driving there, for a split second I thought I smelt something electrical, went away in a second. Maybe I imagined it(?)

    Then I noticed when switching on my headlights, all of sudden my dash light symbols for the headlights didn't turn on/appear. Meanwhile, headlights worked just fine.

    I get to my mechanic's shop. They measure my charging system... and.... zero charge coming from the alternator, also "check charging system" warning comes back on. Mind you the serpentine belt was routed fine and doing its work.

    So right now I'm thinking, could it be that I kinked the PCM control plug wire into the alt which cause a shortcut, causing the headlight dash light fuse to blow? When I was wrapping it with electrical tape at that angle one of the wires seemed scuffed but not egregiously exposed as far as I could tell.

    Again, all advice is highly appreciated! Thank you
  4. 07gts197

    07gts197 forum member

    I don’t remember my 07 gt having a light for the headlights only for the high beams.

    I’d guess it’s that ecu plug, check it again to make sure it’s fully seated.

    Sent from my iPhone using Tapatalk
    Stangabe likes this.
  5. DieHarder

    DieHarder Member

    Your alternator needs the following to work: 1) A ground - typically it comes from being bolted to the engine but I had to add another from the passenger strut ground to a bolt on the alternator to get a good ground. Since yours worked initially I would say your ground is okay but easy to do a continuity check from the that ground to a bolt on the alternator. You should see less than a ohm. 2) B+ cable from the alternator bolt on the back that recharges the battery through the fuseable link. 3) PCM sense lines (Gen Mon; Gen Com; PCM plug pins 1,2) from the ECU that control the alternator output. Pin 3 goes to F43/10A fuse in the BEC fuse box.

    Here's a link to the online manual for electrical wiring and connections for the charging system: System.pdf

    99 times out of a 100 it's something you changed, connected, disconnected, damaged taking it off or reinstalling or what have you. Suggest rechecking your work concentrating on the connections at the back of the alternator (cut and extend that PCM plug if you have to) and make damn sure nothing is even close to the alternator output.

    If you have a VOM do continuity checks on the PCM plug from end to end and check for shorts between wires in the plug. (you can buy a replacement (plug w/pigtail) for ~$10 online if needed). If you find any issues strip away the tape as needed and repair.

    If you shorted something in the alternator it may be gone. Take the alternator off and find an alternator rebuilder. They're the only ones I would trust to tell you whether it's still working correctly or not. I had two auto stores and a dealer mechanic all tell me my very expensive DOB alternator was bad while a rebuilder told me it was fine. It ended up being fine and I'm still using it today. My grounds were bad...thus the reason I always check grounds when troubleshooting electrical issues.
    john knox, 07gts197 and Stangabe like this.
  6. msvela448

    msvela448 forum member

    I agree with having an alternator shop do the testing... (not just an auto parts store) And definitely use a alternator-specific shop for a rebuild. Most states have a good shop, but in case anyone is looking for a good one I've used these guys a bunch of times...

    It does sound like the OP may have pinched a wire, popped a fuse etc. etc. If the OP is going to cut and lengthen the wires use solder, heat shrink, and the same size and quality of wire.

    Sent from my SM-N975U using Tapatalk
    Stangabe likes this.
  7. Stangabe

    Stangabe Junior Member

    Thank you for the replies! Since I'm inexperienced / and easily intimidated by electrical stuff I ended up taking it to my mechanic. He messed around with it for a while, changed the alternator again(!!) and now it works.

    He said my work up to then did look ok, and couldn't explain why my new 2010 alternator wasn't functioning. I'm at a loss for words... Two alternators in a row from Rockauto, one reman one supposedly new, non-functioning?? I'll take the 2010 one to an alternator shop sometime to confirm but it really looks that way.
  8. 07gts197

    07gts197 forum member

    Recently my battery kept dying overnight in my 09 p71. Right before it was decommissioned the agency put a new intake and Ford alternator on it. It was great until a couple months ago I’d go outside to start it and it’d be completely dead. I charged the battery and all was well until it sat over night. It could sit all day no problem. I had a good used alternator sitting in my garage I swapped in and no more issues.

    Moral of the story, just because it’s new doesn’t mean it works. Good thing it fixed itself.

    Sent from my iPhone using Tapatalk
    Stangabe likes this.
  9. justin73

    justin73 Junior Member

    I bought a used alternator from LKQ for 60 bucks for a 2010 mustang. Put it on my 08 gt with no clocking just loosened up the wiring harness from its holders and it worked fine.

    Sent from my iPad using Tapatalk
    Stangabe likes this.
  10. Stangabe

    Stangabe Junior Member

    Definitely a great point! Guess I had to learn it the hard way!

    Hopefully It'll hold up for a fair few years now, but if I ever had to do it again I'll have the new alternator tested before I install it and start doubting my own sanity.
    07gts197 likes this.
  11. Pentalab

    Pentalab forum member

    Typ u will measure 12.2 to 12.5 vdc on the battery terminals. (eng off). With eng on, you should measure 14.5 to 14.75 vdc...right at the battery terminals. If you start the eng, and battery voltage is only 12.XX your alternator is DOA.

    Assuming the alternator is good, and battery voltage measures 14.5 to 14.85 vdc ( eng on), switch the DVM to read AC volts. It should read zero or close to zero. If it reads any amount of AC voltage, you have AC ripple coming out of the alternator.... which means one or more of the six diodes is toast.
    07gts197 likes this.
  12. 07 Boss

    07 Boss Senior Member

    I've had alternators bad out of the box. Last time Ford changed mine I had to wait an extra day while they got a replacement for the replacement.
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