Help - Alternator - Electrical smell
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Test point A to + side of the battery should be 0V, it is the same point.
Not running the point F to ground should be 12V or the drop across the field windings. This should drop to near 0V when a battery reaches full voltage with the engine running. This F voltage is how the voltage regulator tells the alternator how much to charge.
Where are you getting the alternators?
I have heard of some posters say they have gotten three alternators in a row bad from AZ. I do not know if they were bad when they bought them or the poster made them bad.
Not running the point F to ground should be 12V or the drop across the field windings. This should drop to near 0V when a battery reaches full voltage with the engine running. This F voltage is how the voltage regulator tells the alternator how much to charge.
Where are you getting the alternators?
I have heard of some posters say they have gotten three alternators in a row bad from AZ. I do not know if they were bad when they bought them or the poster made them bad.
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Laughing Gas
Joined: Oct 2003
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From: DC
So, if I read you right, all my readings are correct for a non-running test. Additionally, I checked for continuity from the A position on the 3 prong plug, to the left side of the alternator fuse receptical. It read good. Not sure how to check for continuity further upstream (I also ohmed the fuse to be sure it's good). Any other tests I can try?
I'm getting a new alternator from the dealer today so I can be much surer that the alt is good. I'd rather not install an alternator and have my truck fry it though. By the way, the rebuilt alternators are coming from Carquest.
I'm getting a new alternator from the dealer today so I can be much surer that the alt is good. I'd rather not install an alternator and have my truck fry it though. By the way, the rebuilt alternators are coming from Carquest.
Fleet Owner
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From: Easton,Ks
Originally Posted by Joe Finn
So, if I read you right, all my readings are correct for a non-running test.
Originally Posted by Joe Finn
Additionally, I checked for continuity from the A position on the 3 prong plug, to the left side of the alternator fuse receptical. It read good. Not sure how to check for continuity further upstream (I also ohmed the fuse to be sure it's good).
It sounds like you have a different alternator wiring and not like the diagrams that I posted.
Originally Posted by Joe Finn
Any other tests I can try?
You do not happen to have a large current drawing device that you or somebody has installed do you?
Maybe hooked in at the A wire with a fuse?
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Laughing Gas
Joined: Oct 2003
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From: DC
I don't have any large currnet draws, the truck is "bone stock". My '97 system is different than the drawing you sent, all 97-2003 should be the same and I thnk 2004 and newer or '96 and older have similar systems, in fact, according to the Haynes manual, I should have battery voltage from A to the battery + and 0v from F to ground (I have the opposite 0v A to batt and 12.5v F to GRD). I don't have a lot of trust in Haynes though, especially with electrical stuff.
Fleet Owner
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From: Easton,Ks
Originally Posted by Joe Finn
according to the Haynes manual, I should have battery voltage from A to the battery + and 0v from F to ground (I have the opposite 0v A to batt and 12.5v F to GRD). I don't have a lot of trust in Haynes though, especially with electrical stuff.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Originally Posted by Joe Finn
My '97 system is different than the drawing you sent, all 97-2003 should be the same and I thnk 2004 and newer or '96 and older have similar systems
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Laughing Gas
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From: DC
I'll try to scan the diagram from the manual I have. I'm primarily using the text that tells you how to do the tests. What do you recommend as my next step? If I put in a nice shiney new alternator from Ford, I'm gambling that this alternator has an internal short and hoping that the problem isn't on the chassis side.
Edit: I've got the scan. I don't see how to attach it from within the FTE e-mail options.
Edit: I've got the scan. I don't see how to attach it from within the FTE e-mail options.
Last edited by Joe Finn; Oct 27, 2006 at 10:00 AM.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Originally Posted by Joe Finn
I'll try to scan the diagram from the manual I have. I'm primarily using the text that tells you how to do the tests. What do you recommend as my next step? If I put in a nice shiney new alternator from Ford, I'm gambling that this alternator has an internal short and hoping that the problem isn't on the chassis side.
I am trying to help you by knowing how the alternator/regulator works. I am not sure what you have between the alternator and the chassis side.
I can only guess with out the right diagram but the basics are:
The big wire from the stud on the back of the alternator to the battery will go through a fuse device and hook to the starter relay. If this wire is shorted to ground before it gets to the fuse device near the starter relay it would burn up the alternator.
It should have battery voltage on it at all times at the regulator.
The three wire plug will bring in the A wire and the A wire should have battery voltage on it for a reference for the voltage regulator to maintain battery voltage.
Another wire in the three wire (I wire) plug will tell the regulator to start and stop charging, this wire is from either the key switch by way of the charge Ind. or from the PCM.
The other wire is a feed back wire (S wire) from the alternator to the regulator and has been used for different things from time to time.
Last edited by subford; Oct 27, 2006 at 10:14 AM.
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Fleet Owner
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From: Easton,Ks
Originally Posted by Joe Finn
You should have the scan in a few minutes, hopefully it has enough detail.
If the wire from the MEGA fuse through the inline mini fuse 20 Amp to the alternator "A" has to high resistance than the alternator will over charge and get hot.
Your system:
http://i54.photobucket.com/albums/g9...97Charging.gif
Last edited by subford; Oct 27, 2006 at 12:15 PM.
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Laughing Gas
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From: DC
I'll have to check and see if the colors match the diagram. I ohmed the "A" line from the alternator back to the mini-fuse, it was good. I don't know about further "upstream" because I was unsure of the other test point. Looking at the diagram again, it seems as though I go from the A at the alternator to the black/orange wire on the starter relay. Am I getting the hang of this?
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Originally Posted by Joe Finn
I'll have to check and see if the colors match the diagram. I ohmed the "A" line from the alternator back to the mini-fuse, it was good. I don't know about further "upstream" because I was unsure of the other test point. Looking at the diagram again, it seems as though I go from the A at the alternator to the black/orange wire on the starter relay. Am I getting the hang of this?
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Originally Posted by Joe Finn
OK, I guess I have to go do my homework. I'll post what I find tonight. Thanks for all the help so far.
EDIT:
Also the text has been changed, the new A should be the old F and I think they are talking about with the key on. With the key on the regulator would drop the voltage some but with the key off the regulator would not be conducting (no charge) and there would be no Voltage Drop from the A through the brush, field windings, brush, to the F test point. So with the key off and a no loading meter you would get battery voltage and this would not indicate a short in the alternator.
Last edited by subford; Oct 27, 2006 at 12:46 PM.
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Laughing Gas
Joined: Oct 2003
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From: DC
Originally Posted by subford
Test point A to + side of the battery should be 0V, it is the same point.
Not running the point F to ground should be 12V or the drop across the field windings. This should drop to near 0V when a battery reaches full voltage with the engine running. This F voltage is how the voltage regulator tells the alternator how much to charge.
Not running the point F to ground should be 12V or the drop across the field windings. This should drop to near 0V when a battery reaches full voltage with the engine running. This F voltage is how the voltage regulator tells the alternator how much to charge.
Edit: Just erased those changes.
Last edited by Joe Finn; Oct 27, 2006 at 12:58 PM.