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Discussion Starter · #1 ·
I just replace the alternator and battery in my Ford. The instrument gauges started going nuts on the first test drive. I checked the voltage and it seemed normal at idle but as the RPM increases the voltage increases. I recorded it up to 18 V. According to the part shops website, the alternator has an internal regulator. Is there something I should check on the van before swapping out the alternator?
 

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Welcome to the Forum
Don't feel lonely on that issue
They had problems on the wiring harness where it goes into the internal regulator
Look at the stud end closely to see if it is damaged
 

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Discussion Starter · #3 ·
Welcome to the Forum
Don't feel lonely on that issue
They had problems on the wiring harness where it goes into the internal regulator
Look at the stud end closely to see if it is damaged
So that would be the three wire plug on the alternator?
 

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you should have the 3 wire plug and also a stud behind it covered with a boot
 

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This May help you
It is an old post
But good info in it
You may have to scroll up on it

 

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Discussion Starter · #7 ·
you should have the 3 wire plug and also a stud behind it covered with a boot
This May help you
It is an old post
But good info in it
You may have to scroll up on it

I’ll check out that post looks good.
 

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Discussion Starter · #8 ·
The wire in top of the picture is the output, it’s good. Bottom is a ground of some sort, still have to check that. How would I go about checking the connector in the middle?
47928
 

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The one in the middle
I would unplug the harness and look at it
or you may use a test light on it
On the ground at the bottom of the alternator a ground can cause all sorts of problems
If you are not sure if it is OK
Just run a new ground wire
from there to a good clean metal surface
The PDF in the above posts will show you the factory grounds
But you can make another yourself
That will never hurt you
 

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Discussion Starter · #10 ·
The one in the middle
I would unplug the harness and look at it
or you may use a test light on it
On the ground at the bottom of the alternator a ground can cause all sorts of problems
If you are not sure if it is OK
Just run a new ground wire
from there to a good clean metal surface
The PDF in the above posts will show you the factory grounds
But you can make another yourself
That will never hurt you
So using a guide on another forum I did an ohm check between the battery sense and gen com terminals of the alternator. It should have 1000 ohms but the alternator has 1600 ohms. That should mean the regulator is shot on the new alternator, ugh! So I’ll be taking it off and bringing it back to the parts store tomorrow to have them test it and be sure.
 

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Discussion Starter · #12 ·
Two parts stores say the alternator is fine. I have my doubts but here is something else I found on a JustAnswer thread. Tech was giving advice on checking the PCM for the exact problem I have.

“Measure resistance between pin 59 on pcm and chassis ground if less than 10 ohms repair short in generator load input. If same line is 1 volt or more repair short in line. Measure resistance between pin 59 on pcm and gli line if 5 ohms or more repair circuit. Reconnect harness to pcm and turn key on and measure between voltage regulator connector and chassis ground if 2 volts or less replace pcm if voltage is more than 2 volts pcm is ok. Make sure your ground from battery is good as this can effect this. Same with no corrosion on pins to pcm.”

Now according to some clarification the tech gave later, it seems he is talking about pins 20 and 45 on the pcm. Not sure where he is getting 59, because 59 is unpopulated.

“Shold be c123 which is already in first diagram I sent you. Pin 59 should be marked on the plastic that goes to pcm.”

I’ll include the diagrams he used below.

All the checks were good except continuity from pin 20 to pin 45 on the pcm. The tech said to repair the circuit, but I’m pretty sure I’d have to replace the computer.

Am I barking up the wrong tree, or am I onto something?
47930
47931
 

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Discussion Starter · #15 ·

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Good video. I tried what he did with similar results as his bad alternator regular. Only differences are my voltage output is higher and the field reference put out no voltage on his and only half a volt on mine. I’m not sure what a normal heart alternator would do. I’m going to return the alternator and get a new one this evening.
Do let us know the results
There is so many issues with that charging system
 

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Discussion Starter · #17 ·
Everything is running well now. So it looks like it was nothing more than a bad alternator that the part store’s test equipment couldn’t detect. Only time will tell, but I feel pretty good about it.

Depending on the state of the battery charge, the field reference wire noted in the video had from 3-11v on a properly operating system. The wire from the PCM was 1-10v.
 

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That is great
There is a video i saw about the connector bolting into the PCM that they had issues with
Thanks again for posting your repair
Come back and see us
 
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