Alternator not charging
 

I just bought a brand new alt and battery and it still isnt charging. It is reading 12.5v with the car running and that is with ntn on. I put the lights on and it drops to 11 volts. and stays there for a little bit. I have been trying to trace the wires down with little luck. there is a prong going into the back of the alt with three wires. One is red, the other brown and the last brown with a white stripe. If one of these wires is messed up, will that cause it to not let the alt charge? if so can someone please tell me where each of these wires go? I have a wiring diagram so please dont give me a link to another. It is not helping. Anyone that can help me out?

Re: Alternator not charging
 

the red wire is the trigger wire on the 3 harness connector. Check for battery voltage there. You can also back probe this and make a jumper to the bat post and that would cause the alternator to go on when the car starts.

Re: Alternator not charging
 

You need 12v constant on the big red wire and 12v IGN on the BRN wire. BRN/WHT wire doesnt matter

If those conditions are met the alt will charge unless its burn out

Re: Alternator not charging
 

Ok so if I jump the red wire from the harness right to the battery post it should start charging it?

And I should be reading 12v from the brown with the ign turned on?

Re: Alternator not charging
 

Ok i jumped the red wire with no luck.

Also tested the red wire with ntn on and it is getting 12.4v constant. the brown wire is getting ntn, but however the brown and white wire is getting 11.4v with the ign off and 12.4 with the ign on. just to verify, according to what i am seeing from my connecter to the left is the big red, next is the brn/wht and next is the brown.

Could this be my problem?

Re: Alternator not charging
 

Depending on what Alt you bought, a good portion are re-manufactured. I bought a faulty re-built Alt in the past. Gank it and Autozone can test it...... Not a mechanic by trade but that is what I would try along with cleanin' up all my connections with sandpaper and a wire brush......... Not much help in the wiring category for ya..........

Re: Alternator not charging
 

Ok i even changed the brn and brn/wires around and still no charge.

Bitchin_buick, I had them test the alternator before I walked out of the store. Everything tested out perfectly.

Re: Alternator not charging
 

Hoping it was gonna be an easy fix like a faulty re-built Alt. for ya....... Bummer.

Re: Alternator not charging
 

if you have a wiring schematic you will see that the brown wire is just for the idiot light.

Re: Alternator not charging
 

Yea i wish it would be that simple lol.

Re: Alternator not charging
 

Tunedperformanc: so it doesnt matter what the brn and brn/wires are getting then?

I have a new main wire going from the alt to the post, and a new one going from the post to the battery terminal. New battery and new alt. What else could keep my alt from charging? where else should the red wire from the connector be going besides the starter? If there isnt a fusible link on anything would that be preventing it? If so where should they be?

Sorry for the 20q but this is such a nightmare right now.

Re: Alternator not charging
 

dont worry about the brown or brown/white wire. If you jumper the bat post to the red wire on the alternator pig tail, when the engine is running he alternator will put out voltage. If you do a search there are even pigtails for the cs alternator that do just as I stated. If this does not work than the alternator is bad. Since you have run a new wire bypassing the one that goes to the starter than to the bat this has eliminated that part of the circuit.

Re: Alternator not charging
 

Well when I had it tested, everything Tested out perfectly for it, but when put in the car I get ntn. I tried jumping that wire like you said and nothing came from it. still the same results. Testing the voltage at both the battery and the alternator with both showing 12.4v. If that jump is suppose to bypass it and make it charge then Im lost as to what needs to be done. If the battery has a bad cell would it cause it not to charge it? Even if so wouldnt it still show 14v at the alt?

Re: Alternator not charging
 

if the battery had a bad cell the alternator would still charge and the battery would have a lower surface voltage. If the alternator is putting out it should have 13.5-14.5 volts at the battery and at the bat post on the back of the alternator. Looks like you need to take it back to the store.

Re: Alternator not charging
 

When I take it to the store, the test results still show up good. I just had a buddy run me up there real quick before they close. With the car idling at 900rpms the battery runs at 12.2-12.3 and the post on the alt says 12.0-12.1. The red wire from the connecting hareness to the back of the alt has a jump directly to the battery post. Im only letting the car run for a min or so before i shut it off. Pretty much just let it run long enough to check the voltage. dont no if that matters or not. Idk what else I can do To make this alternator kick in.

Re: Alternator not charging
 

No other Ideas?

Re: Alternator not charging
 

other than chucking the alternator through the parts store window ! no .....

Re: Alternator not charging
 

Lmao Im about to that point. Thanks for your help. Ill play with it for a little bit more before I give up.

Re: Alternator not charging
 

I am having the same exact problem with my 92 camaro and I am lost did u ever get it fixed

Re: Alternator not charging
 

No, Still havent had any luck on it. Taking it to my buddies shop on friday. If he can figure it out ill post it up here.

Re: Alternator not charging
 

If it's a standard 10si style alt, doesn't it go:

Big terminal: Thick red cable to batt +
Small terminal '1': Indicator out, brown pigtail. Needs to go thru a 10 ohm 10W resistor, or idiot light bulb, to IGN on.
Small terminal '2': Voltage sense wire, red pigtail, to batt +.

http://www.oldengine.org/unfaq/10si.htm

Has your harness been hacked up or something?

Re: Alternator not charging
 

Check all your grounds. Had same prob. Was bad ground.

Re: Alternator not charging
 

how you making out with this problem i have the same problem . parts stor says the alt is ok but I have it hooked up and i have 12 volts T big wire and i have keyed 12 volts at brown wire still no charge. mine is going back to the store to be rechecked,

Re: Alternator not charging
 

Ive had this problem many times before with many different Camaros and Firebirds/TA's. I took the alternator back and it tested good. Chucking it through the window sounds like a good idea! Everytime with me, it turned out to be the alternator. Now every time I have the problem and it tests good, I demand another alternator. Not saying thats what the problem is with yalls cars but I wouldnt trust Autozone. Im not sure what exactly their machine tests but it sure dont tests if it works in the car!

Re: Alternator not charging
 

my problem last week was the alt. I took it off took it up there they said it was good .It messed me up for a week took it back up there asked someone else to look at it It was BAD.

Re: Alternator not charging
 

I still can't get mine to charge, bought 2 new alternators and still nothing, any help?

Re: Alternator not charging
 

My IROC only has 2 wires though, red, and brown/white.

Re: Alternator not charging
 

with a test light you should have power at the large wire that bolts to the back of the alternator. you should have power on the small wire after the key in on.if you dont have keyed power the problem is in the car

Re: Alternator not charging
 

They both have power, my car only runs for a couple seconds unless I unplug the alternator.

Re: Alternator not charging
 

Ima replace the alternator again after work.

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the small wire shouldn't have power till you turn the key. what yo you get for a volt reading ? you could have a fan relay problem

Re: Alternator not charging
 

My fans just stopped working. Where is the fan relay?

Re: Alternator not charging
 

i think there two of them on the passenger fender well they could be melted together

Re: Alternator not charging
 

Check the "fan" fuse in the fuse block under the dash. This circuit supplies power to both the fan relay and alternator.

Re: Alternator not charging
 

I have 3 relays by my battery, 1 of them doesn't have any numbers on it.

Re: Alternator not charging
 

you need help from someone who has that year i have a 87 . but you have relays for the fan somewhere. I have 3 all together but there for the fuel pump ,maf, and maf burn. my fan ones are on the passenger fender.

Re: Alternator not charging
 

Just replaced all 3 relays and still wont stay running.

Re: Alternator not charging
 

what ones did you replace?

Re: Alternator not charging
 

Front passenger by battery.

Re: Alternator not charging
 

The relays you're looking for are by the brake booster... The fan relay has a large red or orange (can't remember ATM) and a large black with red stripe coming out of it. The FAN fuse under the dash is for BOTH the coolant fans AND the alternator. Which is why it is imperative that you test the voltage on ALL of the alternator plug connections with the ignition on. The wires should read battery voltage. There is a common problem with the GM setup in that the wires at the fan relays overheat and get damaged. A new relay connector usually solves this problem.

Re: Alternator not charging
 

I'll replace it in the morning, both by brake booster, the fuel pump relay has already been replaced. I've spent $1900 on electrical and emissions. Not much left except wire harness.

Re: Alternator not charging
 

:doh: Posted the wrong location... The primary fan relay should be bolted to the edge of the radiator support by your battery, tucked in the corner under the radiator cap. Same wire colors. I can't find a location in my FSM for the secondary fan relay for some reason (not listed in the diagnostic page OR the component location views pages).

Re: Alternator not charging
 

It starts just fine then stutters and dies, if I stay on the gas it'll stay running though.

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The only sensors left are O2, knock, and oil pressure. All other sensors are new. It didn't have an alt problem when I bought it though.

Re: Alternator not charging
 

I think I might have to buy a wire harness, I'm running out of ideas

Re: Alternator not charging
 

Uhm, this may be a stupid question, but did you check the voltage AT the alternator post (+), with your meter on ground (-)?

Because as long as the field coil has power, and the bridge rectifier, all that good stuff is getting power, it should be outputting 13-14v.

If your alternator is putting out 13-14v at the post, but NOT at the battery, then you have a bad main power wire going from the alternator back to the battery. Too much resistance in the wire, or it's clipped.

Re: Alternator not charging
 

All wires have 12 volts, something is telling the alt not to turn on.

Re: Alternator not charging
 

....So is that a yes to my question? You hooked a DMM up to the +post on the alternator, and the (-) on the ground (any shiny metal on car)? Because if you didn't then you need to and record the voltage there. Don't assume just because there is 12v at the battery, that there is 12v at the alternator.

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Yeah, I used dmm, just 12 volts.

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Where does the small wire run to? No book or online is telling me.