New alt and battery still have charging issue

striker911

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Aug 6, 2008
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Mountain Home, AR
I checked all the wires that I could hunt down and nothing is loose. So I ordered new pigtails for the alt connections. I am an auto tech and we have "all data". I looked it up and found that the alt connections where the most common problem in my situation. What I wonder is if anyone else had this problem and what was the fix? We help a few other shops in the area since we can do things others have no tools for. Like alignments and tires. The owner of another shop was their when I was looking the wires over and sujested that I just take the alt charge wire and just run it straight to the battery so it will charge. I havent done that but wonder what u guys think on that idea?

The car starts fine but the problem is that if you load the system up it starts pulling the volt gauge down so the charge is not keeping up. Like if I run the ac and the blower motor is on low its keeping charging voltage but as I turn the blower up the volts go down till its under 12 volts on high. Its not just a blower motor fault since with the headlights on it also pulls the volts down from 14 to about 12.5.

I will put the pig tails on the alt first but if it comes to it then I will try to put the wire from the alt to the battery. Only I want some feedback before hand since I dont want any more problems that might arise from doing that. Thanks for any help guys. One more thing. The alt is a 65 amp and has had no trouble keeping up for the last 8 years so no reason to suspect that I need 130 amps, nor do I want to rewire the car so 130 will work without smoking things. (Its an 86 gt and has factory wiring).
 
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2000xp8

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While i don't know the answer to your problem.
IMO it would be worth it to swap to a newer alternator.
Yes, it's a little more trouble, but any old external fan alternators i've dealt with were garbage.

Did you buy a ford reman or a chain store reman?
Chain store versions have been known to be DOA.

Honestly, if it's a chain store version, return it, get a 3g from ford or a real ford one from a junkyard.
 

HISSIN50

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Did you have the alt bench tested? You might have dropped a diode. That would explain why it can't keep up under high loads, though it used to be able to.

Don't rewire your charge wires, and don't do it without circuit protection. The wire now goes to the battery side of the solenoid anyhow.
 

jrichker

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If this is your car, I am always glad to help my fellow Mustang enthusiast. A lot of guys here don’t have deep pockets or fat bank accounts. This is my contribution to help them enjoy their Mustang without hurting their wallets or aggravating their wives or girl freinds. :D

If this is a customer's car and you are looking for help to fix it, I expect you to send me a check for 1/2 the labor charge you bill the customer for if you fix it using my help.


Familiarize yourself with the following application note from Fluke: See Automotive Test Tools for help for help troubleshooting voltage drops across connections and components. . You will need to do some voltage drop testing of several of the wires.

Start looking for these things:
1.) Bad diode(s) in the alternator - one or more diodes have open circuited and are causing the voltage to drop off as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Do the voltage drop test as shown in the Fluke tech note link. Measure the voltage drop between the alternator frame and the battery negative post. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.

3.) Bad regulator that does not increase field current as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.

4.) Bad sense wire - open circuit in sense wiring or high resistance. The yellow/white wire is the voltage sense and power for the field. There is a fuse link embedded in the wiring where it connects to the black/orange wiring that can open up and cause problems. Disconnect the battery negative cable from the battery: this will keep you from making sparks when you do the next step. Then disconnect the yellow/white wire at the alternator and the green fuse link at the starter solenoid/starter relay. Measure the resistance between the alternator end of the yellow/white wire and the green fuse link: you should see less than 1 ohm. Reconnect all the wires when you have completed this step.

5.) Bad power feed wiring from the alternator. Use caution in the next step, since you will need to do it with everything powered up and the engine running. You are going to do the Fluke voltage drop tests on the power feed wiring, fuse links and associated parts. Connect one DMM lead to the battery side of the starter solenoid/starter relay. Carefully probe the backside of the black/orange wire connector where it plugs into the alternator. With the engine off, you should see very little voltage. Start the engine and increase the load on the electrical system. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.


 

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striker911

Member
Aug 6, 2008
156
1
18
Mountain Home, AR
If this is your car, I am always glad to help my fellow Mustang enthusiast. A lot of guys here don’t have deep pockets or fat bank accounts. This is my contribution to help them enjoy their Mustang without hurting their wallets or aggravating their wives or girl freinds. :D

If this is a customer's car and you are looking for help to fix it, I expect you to send me a check for 1/2 the labor charge you bill the customer for if you fix it using my help.


Thanks J. This is all the info I was looking for and if I cant fix it after all that then I will quit my job lol. Its actually my personal car so sorry no cash in my pockets. I do have other people that have more experience at my shop since im the new guy. One guy can tell u whats wrong with a car in seconds no matter what it is but hes too cocky to help me on mine most of the time. This dude threw a $1,500 injector pump at a diesel without even testing the old one and he was right on the money. He even knows sizes of bolts, locations and tricks to change things out without even looking. Wish I was that good. Anyways;

I did not have the new alt tested but I did however get a cool parts guy at oriley and he changed it out anyways with no receipt even when the old one tested good. So its no surprise that with the new alt its still dropping voltage under load. With that being said I will put on the new pig tales and see. If all else fails at least I will have some place to go that wont hurt the car. Thanks a lot man, your golden. I will keep you guys up to date. Thanks to everyone that had and has any input. :nice:
 

striker911

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Aug 6, 2008
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Mountain Home, AR
Heres an update. I tried all the steps listed and only got to step 4. When I tried step 5 the starter made a popping sound and i think it locked up cause it only clicks now. I do not see how this is related to my charging system per the wiring diagram posted so is the starter cause for my problem or just a casualty of the problem? I am having to drive my gas hog of an f150 now, so that sucks since it get like half the mpg. Maybe I should get a new harness.
 

HISSIN50

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Were you probing the battery-side of the solenoid (the one with all the connections) or the starter cable side (the side with one cable)?
 

striker911

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Were you probing the battery-side of the solenoid (the one with all the connections) or the starter cable side (the side with one cable)?
I did every thing but step 5 and everything checked out okay. For the charging problem I isolated wires and I did not test any thing in direct contact with the battery.
 

HISSIN50

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I'm trying to figure out how you jumped the starter and one thought was that the charge cable of the alternator (which connects to the battery eventually) was connected to the starter lug on the solenoid.
 

striker911

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Mountain Home, AR
I'm trying to figure out how you jumped the starter and one thought was that the charge cable of the alternator (which connects to the battery eventually) was connected to the starter lug on the solenoid.
Oh. Well I never jumped the starter. So far I changed the pig tails on the alt and tried changing the batt and alt. I also ran the test's suggested above but could not get the last test done with the car started cause the car wont start now. Oh ya after it wouldn't start I changed the fender mounted solenoid since I had 2 laying around. No help their.

Ill test the starter when I can get to it.
 

HISSIN50

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Are you sure your battery is properly charged?

I feel like we're speaking different languages here. :(

I might have misinterpreted what you said. I thought your starter spontaneously engaged while you were trying to perform step 5. If this was not the case, I'd have simply stated that step was was never attempted because the car will not crank.
 

striker911

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Are you sure your battery is properly charged?

I feel like we're speaking different languages here. :(

I might have misinterpreted what you said. I thought your starter spontaneously engaged while you were trying to perform step 5. If this was not the case, I'd have simply stated that step was was never attempted because the car will not crank.
Ya I tried to be specific. Sorry about that. So I will try again.

When I tried to perform step 5 I went to start the car and heard a fairly loud pop coming from what seemed to be the starter.

I looked at the diagram above and the starter is not in it. I just wondered if a starter was going bad could it be the cause of my charging problem some how? I am running out of options and maybe just reaching too far out with this? The click from the starter is pretty hard not like the battery is low but like something is screwed up in my wiring or the starter just went out. Seems strange to me that I have two diff problems at once. I had this car for 8 years and never had a starter issue or a charging issue. I hope you see where I am going with this and where my heads at. I just hate to keep throwing parts at it so I am looking for help before I do anything else. Thanks.
 

HISSIN50

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I'm with ya now brah. If I read things correctly, the alt goes wonky when there's a high load, and now your starter is wonky (it itself causes a high load). I would ensure the battery cables/connections and the grounding pathways are very intact. A high load of either variety could show a weak ground or power pathway.

Did the voltage drop-test show a large drop when you had a full load going?

Do be sure the battery is charged. A thunk like that can happen if it's down (amongst other reasons). A jumper battery can help augment things if charging your battery is difficult (no charger or power near the vehicle, etc).
 

striker911

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Aug 6, 2008
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Mountain Home, AR
K guys I finally got somewhere on the car today. Had to get a new starter. I hooked both charging wires together and ran a temp wire to the battery but still nothing had changed. While I had the new pig tales for the alt unwrapped I noticed something. My original alt harness had only 4 wires total, and the new pig tails have 6, with the only addition being two white wires (one on each pig tail).

I had a color change vs pin arrangement problem when hooking in the new pig tails so I ended up hooking the car harness green/red wire to the white/ black wire on the pig tail since it would have placed the green wire in the same pin it came off of. Should I have switched pins on the new alt and just hooked the green to green and left the white wires alone?

Maybe I need to run some wire to put the white wires to use? I hope someone can understand this crap cause I am confused as all get out. So I am going to go ahead and hook green to green just to see if it helps. I hate to shoot in the dark like that but at this point im ready to poor gas over it and light, so what do I have to loose right lol.

One other thing. I also jumped the fuse link on the yellow wire so the fuse links are tested good and yet I still have my voltage drop from over 14 with nothing but the car on to 12 or less with cd player/amp, lights,and ac on.
 

jrichker

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Go back to my eariler post. It has a color coded diagram of what wire goes to what connection.
 

jrichker

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Go back to my earlier post. It has a color coded diagram of what wire goes to what connection.
 

striker911

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Go back to my earlier post. It has a color coded diagram of what wire goes to what connection.

I have that printed and was using it today while troubleshooting. Just not sure you understand my question. On the old alt it had no white wires hooked to it at all cause their was none in the stock harness. So the plugs just had one open space each. Now that I put new pig tales in the harness the plug arrangement did not fit the color code. I decided to take the green wire from the original harness and connect that to the white wire in the new plug/pig tale so the original green wire was plugged into the same pin on the alt. Maybe I got a pig tail that had the two (green and white) wires put in the wrong spots.

Still no matter what this sucks. I still dont see any of this helping since im back to where I started but with new parts that do the same thing the old ones did. I cant see getting a bigger alt or wiring it up different since its worked as is for the last 8 years. This is too strange. What about looking at a bigger picture like computer? Does anything out of the ordinary come to mind. I am out of ideas.
 

HISSIN50

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If you don't have any white/blk wires (or stator circuit wiring), did you have a 6G alternator before? The 6G's handle the stator loop internally.
 

striker911

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If you don't have any white/blk wires (or stator circuit wiring), did you have a 6G alternator before? The 6G's handle the stator loop internally.
I guess thats what I had then. So you think I got the wrong alt? I bet if I just follow the color code and put the green on green it would work then. If that does not work should I put the white wires from the pig tails on the yellow wire? according to the diagram yellow and white both end up being in the same place (From regulator to stator). Or is that just not going to work at all since I may not even have a stator. Sorry if I may sound ignorant but this stuff is all new to me. I never had a charging problem that a new battery, loose wire, or alt didnt fix with no issues.
 

HISSIN50

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The yellow/white wire is the sense-wire for the circuit.

You're missing the white/blk wires, right?

If you're missing the white/blk wires, but your regulator plug has one (that is not connected to anything), you can put a spade terminal on it and run it to the 3G alternator. There will be one lone plug on the side of the alternator that can receive the spade connector you add.

If you have a 2G, you would connect the white/blk wire on the regulator to the white/blk wire on the BBS (rectifier) plug.

Here's a diagram that shows things a little less technically than Joe's detailed diagram. The lower right corner has the alternator portion:

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif