Alternator Problems
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Alternator Problems
I'm on my 3rd alternator for my '03 F-250 6.0, I've searched and read nearly every post regarding alternators and charging systems but still can't narrow down my problem.
Here are the symptoms: when the trucks is cold the alternator is putting out correct voltage (14.4) but as it reaches operating temperature the voltage drops and the charging light comes on. I've load tested the batteries and they check out fine. Both idling in my driveway and driving down the road the alternator will cycle on and off, usually on for 15 seconds on then off for several minutes. Also I noticed that when reading the voltage at the alternator plug one is always on (12+ volts) while the other which is controlled by the acc. switch will read 12+ volts, but as soon as the charging light comes on it drops to 1 volt. I'm stumped someone please help!
Thanks in advance.
Bryan
Here are the symptoms: when the trucks is cold the alternator is putting out correct voltage (14.4) but as it reaches operating temperature the voltage drops and the charging light comes on. I've load tested the batteries and they check out fine. Both idling in my driveway and driving down the road the alternator will cycle on and off, usually on for 15 seconds on then off for several minutes. Also I noticed that when reading the voltage at the alternator plug one is always on (12+ volts) while the other which is controlled by the acc. switch will read 12+ volts, but as soon as the charging light comes on it drops to 1 volt. I'm stumped someone please help!
Thanks in advance.
Bryan
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Just normal operating temp, just less then half way up the temp gage. Nope, no restrictions to the alternator, even happens with the hood is up while idling in the driveway. When the truck gets warm (or it's just a coincidence) the alternator completely stops putting out voltage, then starts up again for a short period.
Originally Posted by gotfu
How warm are you talking about?Alternators will have reduced output when warm.check to make sure you dont have anything restricting air from getting through the alternator. hope this helps
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Originally Posted by gotfu
did all of the other alternators fail the same way?
Is it the alternator or another internal problem, that's the million dollar question?
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From: canada
id start by checking all connections to the alternator sometimes the molex plugs seem to connect fine but are actually loose.ive also seen wires break inside the insulation which causes intermittant problems like you are describing.on my own truck i did have the main charging wire from the alt.come loose where it connects to the battery post,you couldnt see any evidence it was a bad connection untill i removed it and saw it had been heating up between the post and the connector its self.
hope this helps
hope this helps
Hotshot
Joined: Jul 2005
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From: Middle Tn.
Maybe one of the techs will come by and correct me but I think the alternator voltage is controlled by the PCM rather than a built in voltage regulator.
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Laughing Gas
Joined: Jan 2007
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From: Sarasota, FL
what type of alternator are you using? i've never had good luck with "parts stores" and rebuilt alternators. i've learned over the years that some parts are worth buying from the dealer or replacing with OEM.
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Originally Posted by BGMSPD
what type of alternator are you using? i've never had good luck with "parts stores" and rebuilt alternators. i've learned over the years that some parts are worth buying from the dealer or replacing with OEM.
I've checked every wire and nothing is loose, I'll have to check the charging wire for a possible break. Can I use my ohm meter to check the resistance and if so what range should it be reading?
Originally Posted by 69cj
Maybe one of the techs will come by and correct me but I think the alternator voltage is controlled by the PCM rather than a built in voltage regulator.
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From: Stuttgart, Ar
If you're checking a wire for a break you would have virtually infinite ohms. If it's good it would basically read zero ohms. I'm not sure what system regulates the alternator output. I'll see if I can get one of our resident tech's on the horn and find out. I'm interested to know that myself.
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Originally Posted by npccpartsman
If you're checking a wire for a break you would have virtually infinite ohms. If it's good it would basically read zero ohms. I'm not sure what system regulates the alternator output. I'll see if I can get one of our resident tech's on the horn and find out. I'm interested to know that myself.
Posting Guru
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From: SoCal, SD CO. East
pinpoint tests
PM me with your email address and I'll email you a PDF format of the troubleshooting guide for the 6.0 charging system... It's titled Charging System — General Information.pdf and it has all of the pinpoint tests...
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From: Florence,SC
well i wanted to stay away from this site because it looks like its going to hell in a handbasket and the moderators seem not to care, but partsman called me to see if i can help.
i would suggest checking youer fusible links at the battery on the right (passanger) side positive post. the wire you keep probing and the voltage is dropping to 1 volt is the signal wire for the light on the cluster and you are seeing voltage drop when it goes down to 1v.
now incase you dont know how to check fusible link here you go. tug on it pretty hard and see if it breaks. if it is good, unless you havent had any for a while or your super strong, it should not break. there are like 6 links about 10g in size. good luck.
i would suggest checking youer fusible links at the battery on the right (passanger) side positive post. the wire you keep probing and the voltage is dropping to 1 volt is the signal wire for the light on the cluster and you are seeing voltage drop when it goes down to 1v.
now incase you dont know how to check fusible link here you go. tug on it pretty hard and see if it breaks. if it is good, unless you havent had any for a while or your super strong, it should not break. there are like 6 links about 10g in size. good luck.
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Originally Posted by ozx3+1
PM me with your email address and I'll email you a PDF format of the troubleshooting guide for the 6.0 charging system... It's titled Charging System — General Information.pdf and it has all of the pinpoint tests...
Originally Posted by BowTieHatr
well i wanted to stay away from this site because it looks like its going to hell in a handbasket and the moderators seem not to care, but partsman called me to see if i can help.
i would suggest checking youer fusible links at the battery on the right (passanger) side positive post. the wire you keep probing and the voltage is dropping to 1 volt is the signal wire for the light on the cluster and you are seeing voltage drop when it goes down to 1v.
now incase you dont know how to check fusible link here you go. tug on it pretty hard and see if it breaks. if it is good, unless you havent had any for a while or your super strong, it should not break. there are like 6 links about 10g in size. good luck.
i would suggest checking youer fusible links at the battery on the right (passanger) side positive post. the wire you keep probing and the voltage is dropping to 1 volt is the signal wire for the light on the cluster and you are seeing voltage drop when it goes down to 1v.
now incase you dont know how to check fusible link here you go. tug on it pretty hard and see if it breaks. if it is good, unless you havent had any for a while or your super strong, it should not break. there are like 6 links about 10g in size. good luck.
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From: SoCal, SD CO. East
Originally Posted by slorider
Thanks Oz, sent you a PM
First off, thanks for chiming in and helping me out. I gave each of them a tug and nothing? I find it odd that the charging system is cycling on and off, if a link or fuse was blown wouldn't it never charge?
First off, thanks for chiming in and helping me out. I gave each of them a tug and nothing? I find it odd that the charging system is cycling on and off, if a link or fuse was blown wouldn't it never charge?