Archived Charging System

[Monroefiredog1]

My charging system is not charging, I have had the Alt. checked off the truck, it showed it was charging about 13. So I replaced the Eng. Speed Sensor(Crank Sensor) that did not help. So I guess that the ECM is bad huh? Does anyone have any ideas on what else it could be? I need some help here!!!





Thanks

 

[Pawpaw]

If the alternator is only putting out 13 volts, there is something wrong with it.



A "12 volt" battery actually puts out 2. 2v per cell. Six cells times 2. 2 = 13. 2 volts.



To charge the battery, the alternator has to apply a higher voltage than 13. 2. I think most alternators are designed to put out 14 - 14. 5 volts.





Bob

 

[JoeBioDiesel]

Hi Firedog,

The off-car alternator testers really don't work well. An alternator with problems can still produce decent voltage when there is no load applied. You probably just have a bad alternator. Why not have it tested on the truck? Most repair shops have battery/alternator testers capable of loading the alternator. It is possible, but unlikely that the ECM is not controlling the alternator. I'd have it diagnosed before I changed it, for sure.



Hi Bob, static voltage on automotive wet cells is 12. 6V. (2. 1V/cell)



Joe

 

[B.G. Smith]

The voltage output of the alternator is limited by the rpm of the alternator and the field voltage(from the PCM). The alternator output voltage (with out the batteries connected) and with full 12 volts to field will go to 100 volts real quick. The voltage is regulated by the PCM voltage to the field of the alternator. To keep the batteries charged, the regulated voltage should be from 13. 9 to 14. 4 volts or somewhere in that range depending on temperature and charge condition of battery. bg

 

[DJW]

Of no charging conditions, had the red dash light come on one night on a Ford in Barstow Ca on a trip to Texas, I was lucky as a Kragen auto parts store was open, and condition of charging system was checked in front of store in parking lot. The alternator was not charging and battery was in good shape, had results in about an minute,. Had alternator changed also battery, battery was ok but being over 4 years old decided to replace it, (motto Fix it Before it happens) there was no charge for labor. Of checking condition of components, it's best to check under Actual Working Conditions, as that's where they are designed to work not on a Bench. Scrum Down

 

[bmoeller]

The alternator voltage is controlled by the ECM. Check to see if the 120 amp fuse (alternator fuse) in the Power Distribution Center (PDC) is good. If it is blown it doesn't put out full voltage.



I blew mine when I touched the oil filter housing and one of the bolts on the back of the alternator with a wrench.

 

[Xgunfighter]

Let me state the simple thng to check if you already havent. If the main fuse is out the alternator will not charge. Had it happen to me. Reially felt stupid when I found out what it was.

 

[Monroefiredog1]

ALTERNATOR IS NOW CHARGING!!!

MY alternator is charging now, I felt so stupid, I had looked at the Alt fuse, but it didn't seem to be blown. So I assumed it was something else. After a few hundred dollars of replacment parts, It still was not charging so I decided to check the fuse with a test light, and low and behold, it didn't have power going to the alternator. I finally found a fuse and replaced it and it worked. What had happen was that the brushes in the alternator were completley worn out, when that happened the shorted out, blowing the fuse. Had new brushes put in the alternator before replacing the fuse. Thanks for all of your help... . this is a great resourse. .