01 GT Good alt, good battery, no charge - Ford Mustang Forum
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post #1 of 18 (permalink) Old 4 Weeks Ago Thread Starter
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01 GT Good alt, good battery, no charge

I've been trying to sort this issue out for a few weeks now. Couple months ago the battery all of a sudden wasn't getting charged at all. Also just happened to be when we were moving the cars 30 miles to my parents while we went on vacation. Had to jump it twice on the way there, then about 5 miles from their place, I slowed to a stop at a stop sign, engine sputtered and died again, then sputtered back to life with normal voltage (read on the SCT) and was perfectly fine the rest of the trip. Came back, and it was still fine. Drove it home with no issue. Then a week or two ago it did it again, so I pulled the alternator out to test and it was in pretty rough shape. Failed the tests at O'riellys and the bearings sounded like they were about to blow out.

I got a reman alternator, put it in. Still no charge to the battery. Checked the fuses, found the Alt fuse in the junction box near the battery was blown, so I replaced that. All the other fuses there, as well as under the dash are fine. Again, still no charge.

The fusible link LOOKS fine, and I'm assuming it isn't the problem if I'm able to check voltage from the alternator, which is the same as at the battery (off and running). I checked, and cleaned the two grounds on the core support. I haven't crawled under yet to check the block and frame rail grounds, but the car fires right up when the battery is charged enough, so I'm not expecting any issues there.

I noticed the dummy battery light on the dash does not ever come on, even during the test sequence with key on. I'm sure it was on during that first trip when this all started. I swapped the bulb with a different one just rule out a bad bulb, and that had no effect, so the light just isn't getting power. Now, I've seen a couple posts saying that if that light isn't getting power, that also indicates there's no power coming from the alternator, but I haven't been able to find any other information about this.

I have no idea where to go from here. Any ideas? I know there's a possibility that the reman alternator is bad, but it tested good at the parts store, so I just want to try ruling everything else out first.


Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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post #2 of 18 (permalink) Old 4 Weeks Ago
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The alternator fuse hasn’t blown again has it? Maybe do a voltage drop test.
https://themustangsource.com/forums/...system-518580/

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The fuse was still fine. I checked it before giving up for the day last night.

Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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post #4 of 18 (permalink) Old 4 Weeks Ago
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Quote:
Originally Posted by Ashlander View Post
I noticed the dummy battery light on the dash does not ever come on, even during the test sequence with key on. I'm sure it was on during that first trip when this all started. I swapped the bulb with a different one just rule out a bad bulb, and that had no effect, so the light just isn't getting power. Now, I've seen a couple posts saying that if that light isn't getting power, that also indicates there's no power coming from the alternator, but I haven't been able to find any other information about this.
The alternator charge warning system is powered via TWO sources. Fuse F2.5 AND the alternator itself.

IMO the symptom about the charge warning light NEVER coming on is a huge symptom.

So one side of the warning bulb should have good key on voltage being feed from fuse F2.5.

The other side should "ring out" to the alternator LG/RD wire.

With the small alternator connector disconnected, what is the key on voltage measurement of the LG/RD wire?

Here are some other threads about the ballast resister located inside the cluster.

https://www.stangnet.com/mustang-for...-issue.909742/

https://www.allfordmustangs.com/foru...t=262412&amp=1

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-for...-drop-test.56/

1999-2004 MY fuse panel schedule:
https://www.allfordmustangs.com/foru...ml#post2669271

It's always wise to confirm that the correct alternator is being used for the application. Many alternators look the same but have different regulators.
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Last edited by wmburns; 6 Days Ago at 08:59 AM.
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Quote:
Originally Posted by wmburns View Post
The alternator charge warning system is powered via TWO sources. Fuse F2.5 AND the alternator itself.

IMO the symptom about the charge warning light NEVER coming on is a huge symptom.

So one side of the warning bulb should have good key on voltage being feed from fuse F2.5.

The other side should "ring out" to the alternator LG/RD wire.

With the small alternator connector disconnected, what is the key on voltage measurement of the LG/RD wire?

Here are some other threads about the ballast resister located inside the cluster.

https://www.stangnet.com/mustang-for...-issue.909742/

https://www.allfordmustangs.com/foru...t=262412&amp=1

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-for...-drop-test.56/
Thanks, that's alot of good information. I probably wont be getting around to troubleshooting again till tomorrow or Friday. By small alternator connector, I'm guessing you mean the one with the two wires going into the regulator? Where exactly is this ballast resister located? I had the cluster out but don't remember seeing anything like that.

Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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post #6 of 18 (permalink) Old 3 Weeks Ago Thread Starter
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Quote:
Originally Posted by wmburns View Post
The alternator charge warning system is powered via TWO sources. Fuse F2.5 AND the alternator itself.

IMO the symptom about the charge warning light NEVER coming on is a huge symptom.

So one side of the warning bulb should have good key on voltage being feed from fuse F2.5.

The other side should "ring out" to the alternator LG/RD wire.

With the small alternator connector disconnected, what is the key on voltage measurement of the LG/RD wire?

Here are some other threads about the ballast resister located inside the cluster.

https://www.stangnet.com/mustang-for...-issue.909742/

https://www.allfordmustangs.com/foru...t=262412&amp=1

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-for...-drop-test.56/
I made some progress, but left more confused than before.

If I measure from the LG/RD wire in the small harness, to its pin on the cluster, the batt light does NOT come on. However, if I go from the harness wire, and touch across it's pin with the pin next to it (which is unused), it DOES light up. Touching just the pin next to it, predictably has no effect. Light only comes on when both pins are touched. I took a peek behind the PCB, thinking maybe the solder on the two pins are shorting each other out or something, but they looked fine, and also verified that that far side pin has no power coming off it on the PCB.

I wasn't able to get a voltage reading while the light was on. I checked but it just read 0. I suck with wiring though, so I may well have just been on the wrong meter setting. That was with the voltmeter set to 20. If set to 2 = .004, and 200m = 1.4, if that means anything to you.
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Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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post #7 of 18 (permalink) Old 3 Weeks Ago
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I'm very confused by your reply. Just wondering. Does your VOM actually work? If you test the VOM by using the car's battery? Are you sure your VOM on the DC scale? If measuring on the AC setting I could see that giving incorrect readings.
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Yeah it works fine. Tested it on a new AAA battery just now and got 1.6v. Was reading correctly on the car battery as well, and it is on DC. I mean there's a chance I could've bumped the toggle button and not realized but I doubt it.

Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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Since you have the ability to isolate the cluster from the car, I suggest measuring the Ohm resistance of the cluster ballast/bulb circuit of the circuit. With the VOM on the resistance scale zero the meter. Disconnect the two cluster connector from the cluster. Towards the cluster measure the resistance between connector C220B #11 (PK/BK) and C220A #5 (LG/RD). Post.

Next "ring out" the LG/RD wire from the body cluster connector C220A #5 (LG/RD) towards the small alternator LG/RD wire. The purpose is to verify that the wire path is good.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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Quote:
Originally Posted by wmburns View Post
Since you have the ability to isolate the cluster from the car, I suggest measuring the Ohm resistance of the cluster ballast/bulb circuit of the circuit. With the VOM on the resistance scale zero the meter. Disconnect the two cluster connector from the cluster. Towards the cluster measure the resistance between connector C220B #11 (PK/BK) and C220A #5 (LG/RD). Post.

Next "ring out" the LG/RD wire from the body cluster connector C220A #5 (LG/RD) towards the small alternator LG/RD wire. The purpose is to verify that the wire path is good.
So, testing the connectors on the cluster;

C220B #11 (PK/BK) -> C220A #5 (LG/RD) = No Reading
C220B #11 (PK/BK) -> C220A #6 (Unused) = .61

Just out of curiosity, I tested #5 against another pin and actually got a reading;

C220B #12 -> C220A #5 = .42

These were all done on the 20M Ohm scale, zero'd out before each test, and checked multiple times.

Ringing out the #5 wire at C220A to the wire at the alternator gave a reading of 0.00 all the way down to the 200 Ohm scale. From what I understand I should be getting at least a little resistance, so this doesn't seem right. Also unsure why there's no reading between the #5 and #11 pin on the cluster, but there is between #11 and #6, which isn't even used.

Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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post #11 of 18 (permalink) Old 3 Weeks Ago
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Just an FYI. Went doing Automotive style Ohm testing the 20M Ohms scale is usually too high. The Ohm values being read are usually fairly low.

I'm going to assume that your test results are accurate and no mistakes were made.

The alternator warning light ballast is a 400 Ohm resister in parallel to the warning bulb. So the cluster warning circuit should have at most 400 Ohms of resistance (slightly less because of the bulb). So the fact that you are showing an "open circuit" means there is some damage inside the cluster.

Plus getting values on unused pins could mean some internal contact "bridging". I would certainly be thinking water damage.

Here's some information about a possible DIY cluster repair.

My odometer goes on and off?
https://www.allfordmustangs.com/foru...f.html#2657361

For a test, try jumping +12 to alternator LG/RD wire. Best to start with a test light and then switch to a fused jumper with the motor running. What we are trying to see is IF the alternator will start putting out.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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I'm sorry, I'm confused about what you mean by "jumping +12 to alternator wire". I'm assuming you either mean to jump the #12 and #5 wires on the connectors to bypass the cluster, but if that's the case should I not jump it to #11 since that's where the current should be going? Or do you mean +12v to the alt LG/RD from the battery?

That DIY is handy, I'll have to pull the PCB off completely tomorrow to more thoroughly inspect for damage. I agree, I'll be surprised if it's not just the cluster in end.

Also, I appreciate the help, and I apologize for my wiring ineptitude. I ******* hate electrical issues above all else, I'd rather blow a head gasket.

Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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post #13 of 18 (permalink) Old 3 Weeks Ago
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Quote:
Originally Posted by Ashlander View Post
I'm sorry, I'm confused about what you mean by "jumping +12 to alternator wire".
Take a piece of wire. Put one end on the battery positive. Back probe the LG/RD hence creating a "jumper" to power the LG/RD from an alternate power source.

Anytime power is injected from an alternate source it's best to use a fused jumper.

Powering the alternator LG/RD wire from an alternate power source will "prove" that the alternator itself will work IF provided what it needs.

2003 GT Convertible (sold & missed)
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post #14 of 18 (permalink) Old 3 Weeks Ago Thread Starter
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Quote:
Originally Posted by wmburns View Post
Take a piece of wire. Put one end on the battery positive. Back probe the LG/RD hence creating a "jumper" to power the LG/RD from an alternate power source.

Anytime power is injected from an alternate source it's best to use a fused jumper.

Powering the alternator LG/RD wire from an alternate power source will "prove" that the alternator itself will work IF provided what it needs.
I figured that was probably it. I used a 20amp fuse and jumped the batt + to the alternator LG/RD and made no difference. I saw another post you made from a few years ago where you mentioned the possibility of the alternator being incorrect and suggested jumping the #1 and #2 pins on the alternator connector, which I tried also, to no avail.

Also tested resistance between the alt post to the battery, and the case and got OL with the positive probe on the post, and 0.00 with the pos probe on the case. This was using the lowest ohm setting. From my understanding 0.00 indicates a short.

On the cluster, I was able to verify continuity from the #5 LG/RD pin throughout it's entire circuit all the way across the board, until it reaches a diode just before the larger harness on the other side. I get OL both ways on this diode, but do as well on every other diode on the board except for 2 or 3 of them, so I'm assuming they just have some sort of protective coating on the ends or something, thats preventing a good connection. I have no continuity through this diode (nor any similar diodes on the board) from any points before or after though. #5 still has continuity to the #12 pin in the other connector though. What circuit is this pin for? Having a hard time finding a diagram of these connectors.

Now, strange turn, you'll probably jump down my throat over this, as I know it's something you're not supposed to do. I'm not sure why I decided to try it, but I did. I quickly touched the same 20amp fused wire to jump the + batt terminal to the alternator case, and the voltage immediately jumped up to ~13.5 and remained there until the car was shut off, then it had the same no-charge problem when started back up again. This completely baffled me. Now I'm not sure if it's the reman alternator, the cluster, or both.

EDIT: I got this alternator from somewhere else as a reman for an '01 Mustang DOHC', but at O'Riellys, the part number on the case (Ultima 01-3729) rang up as an alternator for a Crown Vic, forget the year they said. I brushed it off as incorrect since those all had the 2v engine which afaik aren't interchangeable, and I was unable to find anything online about that part number aside from a link to O'Riellys of a completely different unit for GM applications. However after doing some more research, it seems some of the Crown Vics could have used a similar alternator, and the wiring on the harness in the 03+ years is different. The LG/RD wire on the 03+ Vics goes to the PCM instead of the charge light, which would definitely explain some of the issues. Is this actually a possibility, and how could I test this?

Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed

Last edited by Ashlander; 3 Weeks Ago at 02:32 AM.
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post #15 of 18 (permalink) Old 2 Weeks Ago Thread Starter
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I'm almost positive now it is in fact the wrong Alternator. Had the alt tested on the car while it was running and it said the regulator wasn't working, which would be due to the LG/RD wire going to the gauge cluster instead of the PCM as it does on the Crown Vics. Gunna take it back and get one from somewhere else, and hopefully that's all it is.


Present
2007 Mustang GT - 5-Speed, Airaid CAI, 4.10s
2001 Mustang GT "Mock 1" - 5-Speed, 03 Mach 1 Swap, 98 Cobra Intake Cam Swap, BBK CAI & Longtube Headers w/ H-Pipe, 4.10s 302 rwhp / 310 ft-lbs
2015 Ford Fiesta - Wifes

Looking For
1981-82 Mustang Cobra/GT T-Top

Past
1984 Mustang GT T-Top - Bare Chassis
1984 Mustang GT350 - 302 / 5-Speed
1984 Mustang LX - 302 / 5-Speed
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