kids hooked up charger backwards

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splitty

splitty

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Well I came home from work and this kid put a new battery in his 85 d100 318/2wd and had it hooked up backwards, with a charger on it also. Now the alternator is not charging. I have a tester that will test at the battery for incoming current, am getting nothing. Did the old pull the pos. cable off with it running engine stalled. I put an old alternator I had on the shelf on still nothing. This alternator could be bad I honestly don't know. Has anybody done this before and what else could have gotten cooked? Voltage reg possibly. It runs perfect just no charge. Thanks for any help, If I can limit it to as few trips to the parts store as needed it would be great.
 
Does it start and run with the key?

Here's what you could have damaged:

Fuses / fuse links and there could be several in that vehicle. Look around up at the bulkhead connector for "tagged" wires or obvious burned / melted insulation

Could have killed the alternator (diodes)

Ditto regulator

AND any other solid state "stuff" in the car, including radio / stereo

This could turn out to be an expensive life's lesson. It pays to take "an extra second."
 
The truck runs and drives perfect. Everything electrical works. Unfortunatly it don't have an am meter. When I got home it was on a charger. I checked their battery install and it was backwards. Red to neg, black to pos. I switched them and the truck started. I was surprised it did. He drove the truck and after a couple days he went to start it and the battery was dead. I went over there today and put another battery in it and it fired right up. I drove it to my shop pulled it in and pulled the pos battery cable and it stalled immediately. I was hoping the extra alt I had would take care of it. Like I said I have a charger that will test the alternator in the vehicle while running and I am getting 0.0 on that. I am not good at electrical diagnosing so this could be a hair puller for me. I saw another thread that explained some steps to narrow things down. It was like reading greek to me but I will start with that and see if I can get that far.
 
Thanks sport, Im headed to parts store to get the alts checked and will get a vr because of the reversed battery wires couldn't have been good on it.
 
After reading your second post there surely must be a fuse link in the alternator main charge line circuit. When you hook a battery up backwards to an alternator it becomes a dead short.

I'm VERY surprised they didn't damage something else.
 
So what are thinking just the fuse link?
 
That's what I'd check first. See if you have power at the alternator output stud. Sometimes when fuse links "blow" they leave enough to "show power." So you might have to put a load on it to be sure.

Also check the voltage at that output stud when running. If the voltage is exactly same as battery, below 13.5, it's not charging, say, 13, 12.6, or less

If the voltage is quite high, way above 14, then it's trying to charge but the charge line is open.

I still cannot believe how lucky you appear to have been.
 
luck is running out. lmao... I unplugged a big black plug on the inner fender cleaned it cause I noticed some minor corrosion plugged it back in and tried to start it and now it just clicks at the box it was plugged into. The red wire had the insulation burned up for va few inches so I am repairing that now and will try your advice next. Oh joy...
 
Ok changing that wire got it running again. Going to try your test now.
 
With my pos meter the battery shows 12.08. The stud shows 10.80 with key off, 10.67 with key on and no change when starting it.
 
I'd say there's a blown link in there somewhere.

Often, a blown link will make "just enough" contact to operate a meter which takes very, very little power

"Just how little..........."

Like your fingers on both hands

Put one probe on battery positive

"Clamp" the other probe in one hand with your wet fingers

Touch your wet fingers on your opposite hand to ground, engine, etc.

You will find that the meter reads "some" voltage going through your body.
 
Kids huh? LOL!!! If my poor kids only knew how many of my F-ups they've gotten blamed for, ( wrong clothes in the dryer, broken plants, toilet seat up, etc etc etc!) Its your story pal!
 
My kid and his friends did that same thing once. Lucky I was standing there to jerk it back off. This was on a GM and the Alt wire that runs down to the starter had a fusible link down next to the starter that got hot but didn't fry.
 
It wasnt my biological kid, just one of my kids from the community. His dad was a very good friend of mine that passed away way to young. Believe me I don't hide my mistakes Id tell ya if I did it. lmao.

I found a fuse able link bad. I will replace it tomorrow. I jumped around it and got 11.64. on the stud of the alternator. the battery was showing 12 volts even. The field wire closest to the stud shows 11.64 the same as the stud with it running. If that tells anybody anything I'm open to suggestions.
 
Also without the jumper around the fuseable link I have nothing at the alternator.
 
The diodes in the alternator were blown by the backwards polarity. This happens when you hook up a battery backwards, hook up jumper cables backwards etc. Likely your replacement (unknown) alternator also has bad diodes, or bad brushes. You need a new alternator in my opinion.
 
Maybe, maybe not. The fuse link is blown, that is for sure.

You have not tried running it with the link temporarily jumpered, is that right?
 
With it running I got 11.64 at the stud and at the field wire. I didn't test the second field wire.
 
I have an update on the truck and would appreciate some advice. I replaced several burnt wires, a fuseable link, had the first alternator tested, it passed three times because I didn't believe it, replaced the voltage regulator. Now: not running at the battery I get 12.45 at the alternator 12.43. With it running I get 14.65 at the battery and 14.85 at the alternator. Sounds pretty high but the battery was pretty low 11.45 from starting and testing with key on for eight or nine hours straight. Any advice would be greatly appreciated because I don't want to burn this kids truck to the ground.
 
It's not charging. Should be above 13.5 running "fast", optimum is about 13.8---14.2 warmed up. These have temperature compensation

A few simple tests

Key in "run, " engine off measure voltage at the

(I'm going by traditional colors, don't have a diagram for yours)

blue field wire, should be a blue and a green field wire.

Blue should have 12V with key in run.

If you have trouble identifying the two field wires remove both field wires and unplug the regulator connector

Only ONE field wire should have power, key "on." Hook this wire back onto the alternator. It does not matter, electrically, which field wire is which

Now take a clip lead on the second alternator field terminal. Touch / "untouch" it to ground Again, with key in "run" you should see a small spark.

Hook this clip to ground, start the engine and slowly bring up RPM. It should show a charge. If not, double check alternator output stud and battery voltage. It should be "coming up" in voltage with engine running "fast idle," or to simulate low/ med. cruise RPM
 
Thanks man, I will check it out tomorrow and get back with results. I think the field wires are red and white. Not sure right now, tired and sight isn't as astute as it used to be. I really appreciate your guidance 67.
 
If you know where I can download a wiring diagram or shop manual for your rig, that would help both of us.
 
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