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Alternator ground/ parasitic draw found

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26ftcobraBBF

Alternator ground/ parasitic draw found

Hey bullnose buds,
Got a question for y'all. I recently replaced the alternator and voltage regulator. There's a stud on the alternator housing (I assume is for a ground wire,) that has no wire going to it, if infact there should be a ground wire that attached to it where should I ground it to the body? Battery? Frame?

Also just a FYI, I've been fighting a major parasitic draw since I've had this thing. Even the guy before me said to always disconnect the house battery when not in use because it'll draw it down quickly. Over the years I've forgot a few times for extended periods, and completely destroyed at least two batteries. Come to find out it was my battery isolator. I don't know how, maybe one of you guys know and could shed some light on how an isolator can fail, and cause an issue like that.
Talk soon

Mike
'85 Ford Cobra Econoline E350 7.5L carbureted thing of beauty

Gary Lewis

Re: Alternator ground/ parasitic draw found

Administrator

Yes, the alternators usually have a ground stud. But unless you do as I've done and powder coat the alternator and the brackets and bolts, it'll ground through the mounts. But it will not hurt to ground it, and if you do then I'd go to the engine's ground stud where the ground cable from the battery comes in.

As for the isolator, if it is a "smart" isolator it has sensing circuits, and if they go bad then there's a current draw.

Are you looking for a replacement? I like the Cole Hersee Smart Isolators. They don't parallel the batteries until one of them gets to a voltage that proves it is getting charged, which makes sure your system is functioning.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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kramttocs

Re: Alternator ground/ parasitic draw found

Administrator

In reply to this post by 26ftcobraBBF

The motor should have a ground stud behind the alternator so if you do want to ground it, you can use that.

Was adding an electric choke the other day so just mentioning that my 1G has GRD by a stud near the Field one (maybe to avoid mixing it with the STAtor).

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio

26ftcobraBBF

Re: Alternator ground/ parasitic draw found

In reply to this post by Gary Lewis

Well I bought a battery isolator off ebay, it was pre-owned and looked to be in decent shape. Today I installed it, I pulled up the website read through the installation recommendations. I ended up up-grading the wire from #10 to # 8 as suggested for a 70 amp alternator with less than 15' of wire. Straight run from the alternator to the "A" terminal on the isolator, the terminal 1 went to the start battery, and terminal 2 went to a 50amp self reseting breaker, then to the coach/house battery. Started her up to check voltage, before I could grab my multi meter the battery isolator "A" terminal was smoking. Shut her down, and disconnected.

One thought I had is I noticed that there wasn't a nut on the lower half of the stud on the battery isolator, so I essentially just tightened it down to the black . In hine sight I think that terminal 2 got cut and grounded to the edge of the isolator housing. Would that cause the A terminal to want to melt down. I'm going to be adding some bottom nuts tomorrow to give some clearance. And try it again.

Mike
'85 Ford Cobra Econoline E350 7.5L carbureted thing of beauty

Gary Lewis

Re: Alternator ground/ parasitic draw found

Administrator

If you shorted Terminal 2 to the case, and assuming the case was grounded, the connection with the most resistance would overheat. And that could easily have been Terminal A.

But is that black spot on your wire to the battery where it goes over the cap paint or a burn?

So maybe you didn't fry anything and can space things up and be ok. But the black of the top of the isolator where the nuts touch is plastic, right?

Gary, AKA "Gary fellow": Profile

26ftcobraBBF

Re: Alternator ground/ parasitic draw found

Yes the casing is grounded. The battery you see in the picture is the house battery. The dark spot on the cable is paint I believe. It's been there as long as I've had it. Plastic is correct. Im hoping I didn't fry anything also. I moved pretty quick to shut it down when I seen it getting hot.

Mike
'85 Ford Cobra Econoline E350 7.5L carbureted thing of beauty

Gary Lewis

Re: Alternator ground/ parasitic draw found

Administrator

You probably didn't hurt the isolator as you had the output of the alternator grounded - if your theory is correct, and it seems like it probably is. So the input of the isolator never got to 12v.

Now, you didn't do the alternator any favors, but if it didn't last long maybe you didn't fry some of the diodes in it.

Gary, AKA "Gary fellow": Profile