2003 f350 6.0l single alternator

Replaced alternator a couple weeks ago with one from napa, noticed a humming with key on and the engine off . Traced it to the alternator, called napa they said it was not normal come get a replacement, put the new one on same thing. Charging in the 13.5 to 14v range the case of the alternator seems to get hot quickly when running. Any6one with some thoughts on this?

Thanks

 

does anybody else have a alternator that hums/buzzes with key on

 

I have heard a few whine when the engine was running, especially with a large load on them, but not when the key is on but the engine is off. How long is the warrenty? If it's working otherwise, maybe you can run it for awhile and see what happens.

 

3 yr warrenty , so you would agree no noise when it is not turning and key on? I have taken a voltage check at the pig tail( two wire) and both are very close to battery voltage +/- 0.25v. The sound would Be simaliar to a light ballast hum (just not as loud)

 

The alternator should not hum or make any noise with thr key off or not running....

 

key on engine off?

 

I have done some testing, my field voltage is the same as the battery voltage and this is wrong it should be between 1-3 volts until running and it suppose to go up to 9 volts. I have been tracing wires but it is a mess and I having a hard time at. I have found the the indicater bulb is blown and for what I ve read this can be the cause of high voltage (batt voltage) on the field voltage. I dont know if this will fixit. Im going to get a bulb. I have a pfd of the charging system but can not seem to get it to attach

 

The bulb is not blown my scew up

 

after more testing putting 12v into the instrument panel and it puts out 12 volts on the output side

 

If the field voltage was too high, your output from the alternator would be too high. Your voltage readings in your first post seem correct so from those values, your field control must be working properly.

 

I agree my field voltage is off and I believe it is controlled in the instrument panel by the indictor bulb or bulb and a diod but I dont know for sure. My testing keeps bring back to the instrument panel. It costs close to 200.00 to have a expert try to fix it and a 2hr drive. My local wrecker is getting me another one for 200.00 same year amd month make, I hope it works

 

I read your post wrong my field voltage is always battery voltage which is wrong it should be 1-3v koeo and 9v running I have no idea why my charging is at 14.5v and not higher. It could be Im using the wrong terms for voltages. on the alternator I get battery voltage at the post, battery voltage at the left wire on pigtail and battery voltage on the right wire at pigtail(this one should be1-3v) koeo

 

The field voltage will not have a certain voltage when running. The field voltage will vary depending on the needed output of the alternator. The field is what the regulator uses to control the output of the alternator.

The signal from the instrument cluster is there only to bring the alternator "online" when the key is in run, so it won't discharge the battery with the key off.

You didn't have any trouble till you replaced the alternator correct? If so, I would suspect the alternator, even though they gave you another.

 

I relaced the alternator because the first one would some times generate and sometimes not and lots of black on the case all the way around on the back half. I did not notice any humming before but that does not mean it wasnt there as it too a week to notice it with the first replacement alternator as I had been doing alot of testing with the key on,. My calling the wire from the instrument panel the field wire is my fault and my lack of proper terminology ...sorry Im going with the instrument panel put out to much voltage . and Im going to check and see if my alternator off my 93 7.3l will fit I know its good

 

I have solved my humming/ Buzzing problem on a 2003 Volkswagen New Beetle 2.0 AVH GLS 2dr Hatchback. I know it's not a FORD, but same issue could occur on one of my Fords. Humming was coming from the alternator, but I was not sure that it was caused my brand new Re-Manufactured alternator, as this new alt was putting out 14.38volts as it should, when the engine was running. But Alternator humming with the engine off and key out, was draining the brand new battery (02/16 WM MAXX 5yr) from 12.68v to 12.22 volts overnight. (tested over just one cool (say 45F) night.)