Please help with PIA alternator issue...

[LEAVNYA]

That wire is just there to let the alternator know to excite.

You could put your DMM on the grn/red wire with the key off. It should read zero volts. I suppose the ignition switch could be bad, causing it to stay hot at all times but you should see other circuits staying hot when they should be off.

I would also do current-draw testing again. This time get a baseline. Then disconnect the rectifier plug and see if the draw changes. If not, disconnect the regulator plug and see if it changes. If neither change, the issue should not be in the alternator circuit.

I left the car at work for the night. The last draw test I did before everything checked out, I had a bad draw when the regulator plug was connected. I have replaced the yellow/white wire all the way to the solenoid and new fuselink. The white/black wire is the stator. The only thing left is the green/red wire however, the battery light is good in the dash, that should indicate that the resistor is good too right? I want to double check the current/draw situation but if it indicates that the draw is in the regulator circuit where do I go from there?

thanks

 

[LEAVNYA]

I'm going to start back to work her around lunch tomorrow. Do you have any advice on tackling the wire in dash? What should I look for/test next?

Thanks for the help,

-Matt

 

[HISSIN50]

If your battery light proves-out and then functions normally, it should be fine. Again, if that wire does not show any voltage with the car off, it should be fine. Also, if the draw doesnt change with the regulator unplugged, the excite wire should be fine.

If the draw goes down with the rectifier-plug disconnected, that suggests a bad diode pack. Not much you can do but swap it out.
The draw could be coming from somewhere else however.

Good luck.

 

[LEAVNYA]

If your battery light proves-out and then functions normally, it should be fine. Again, if that wire does not show any voltage with the car off, it should be fine. Also, if the draw doesnt change with the regulator unplugged, the excite wire should be fine.

If the draw goes down with the rectifier-plug disconnected, that suggests a bad diode pack. Not much you can do but swap it out.
The draw could be coming from somewhere else however.

Good luck.

The Green/Red wire doesn't show voltage with the key in the off position. The draw (4.8 amps) goes away if I unplug the regulator plug.

 

[HISSIN50]

Wow, a 5 amp draw is HUGE. I'd recheck the charge cables for shorts (again) and then have the alt tested and swapped out.

 

[LEAVNYA]

Wow, a 5 amp draw is HUGE. I'd recheck the charge cables for shorts (again) and then have the alt tested and swapped out.

First off, if you look back a few posts, I replaced the alternator (again) two days ago. The old one had a bad diode. The problem (DRAW) hasn't changed throughout alternators. If I put the alternator off of the other mustang we have, the draw is still there.

If I disconnect either plug (Rectifier or Regulator) the draw goes away. If I re-connect both plugs and cut the White/Black (STATOR) wire, the draw goes away.

 

[HISSIN50]

First off, if you look back a few posts, I replaced the alternator (again) two days ago. The old one had a bad diode. The problem (DRAW) hasn't changed throughout alternators. If I put the alternator off of the other mustang we have, the draw is still there.

If I disconnect either plug (Rectifier or Regulator) the draw goes away. If I re-connect both plugs and cut the White/Black (STATOR) wire, the draw goes away.

Ok. Since you brought up the first batch of testing, you had noted that the alt was fine, then later noted it was bad. It very well could be bad again. Personally, I've had a couple alts in a row test bad right off the shelf (I make sure they're bench tested before I even pay for one). There's a lot of junk out there.

You have noted replacing wiring. This means nothing from the OEM alternator or wiring remains. Yet the issue is still there. So I would be thinking that either the alternator is indeed bad (again) or that there is still a wiring issue. A bad diode is hidden when testing on the car with the rec-plug disco'd - that's why the draw falls off when the plug is removed.

Your manual might have specs on testing the stator circuit. Feel free to go through that if you want, but if the wiring was properly replaced as was noted (the stator is just a loop), the wiring should be fine.

Alts can pass tests and still have issues. Often, the machines and techs/parts people see test/test results as black and white and it's not always the case (like if you drop one diode, you lose max output but the alt works alright otherwise).

Good luck.

 

[LEAVNYA]

Ok. Since you brought up the first batch of testing, you had noted that the alt was fine, then later noted it was bad. It very well could be bad again. Personally, I've had a couple alts in a row test bad right off the shelf (I make sure they're bench tested before I even pay for one). There's a lot of junk out there.

You have noted replacing wiring. This means nothing from the OEM alternator or wiring remains. Yet the issue is still there. So I would be thinking that either the alternator is indeed bad (again) or that there is still a wiring issue. A bad diode is hidden when testing on the car with the rec-plug disco'd - that's why the draw falls off when the plug is removed.

Your manual might have specs on testing the stator circuit. Feel free to go through that if you want, but if the wiring was properly replaced as was noted (the stator is just a loop), the wiring should be fine.

Alts can pass tests and still have issues. Often, the machines and techs/parts people see test/test results as black and white and it's not always the case (like if you drop one diode, you lose max output but the alt works alright otherwise).

Good luck.

I'm happy, excited, pissed and frustrated, all at the same time. The first two alternators I received were aftermarket o'reilly's. When I first went in to purchase the alternator I explained I needed the pigtail/plug for the rectifier because the alternator I had just taken off was hard wired. After all of this work and bugging you to death, the rectifier pigtail he gave me was for an earlier model Ford.

He just went a grabbed it and didn't look it up in the system. The plug he gave me was: White/Black-Black/Orange I Black/Orange ( " I " Being the molded slot to keep you from reversing the plug). What I needed was Black/Orange-Black/Orange I White/Black. The only way I figured that out (and I don't believe I would have otherwise...) was that the latest alternator they gave me was a Motorcraft re-man instead of their blank backed O'reilly's. So the Ford has the cast rectifier schematic in the casing/housing on the back behind where the plug goes in.

Looking at all the schematics that were referenced to me here, I still can't tell the orientation for the plug from the schematics. Of course I do have another Mustang and should have cross referenced that, but I took for granted the plug was right. The regulator pigtail.plug was replaced too, but I went and pulled that at the store myself.

Thank you again for all of your time and help. Maybe you can throw this experience in your bank of knowledge. "Check to make sure you have the right rectifier pigtail/plug if you replaced it."

Problem solved, PM me your address and I'll send my thanks for your help.

thanks again,

-Matt

 

[HISSIN50]

Matt,
Nice work!

Pat yourself on the back for your diagnostics and observations. We try to do all we can from a keyboard but crap like what you went through is the kind of thing that no one but the end-user can diagnose. I could have made 100 guesses about what was wrong and never guessed correctly.

On the plus side, I'd happily take a Motorcraft reman'd alt (hopefully for the price of a cheaper unit). It should hold up nicely for ya.