I know this subject has been gone through before, but here we go again. I have load tested the batteries and they are perfect. The alternator is putting out 14.5 volts at the alt., and at both batteries. All battery and electrical connections were taken apart and emery clothed. Cables are perfect with no resistance. Put on a new belt. Oil has been changed 500 miles ago. The light flickers part of the time, is on part of the time, and is completely off part of the time. Steady throttle going down the highway, it isn't on, but the rest of the time, it is intermitant. Any other suggestions. Thanks

 

Possibly the voltage regulator? IDK. It almost sounds like the alt is putting out the volts but not the amps. I don't know if the voltage regulator is built into these alts or not. Just trying to put some possibilities into words for someone who knows the answers.

 

My battery light was blinking intermittenly last fall.. Turn out to be one of the two small wires that come off the top of the altenator was rubbing the altenator housing, down about 1 &1/2"' from the connector..(these wise are too short from the factory) . I had to use a magifling glass looking at the insulation on the green wire to see the bear copper showing thru.. you could not see it with naked eye.. Rerouted the wire abit and wrap tape around it and it has been good ever since..

 

I gave a quick visual of those two wires, (seen that post awhile back) but will check again a little closer.

 

I just fixed mine last week. It was doing the same thing, but it was corrosion on the positive battery terms. If all the cables/connectors are good, the batts load test (separately) good, and the Voltage is correct, I would think the next step is to pull the alt and have it load tested. Most (all?) parts stores will do this for nothing. Since it comes out so easy, you should be able to take it out at the parts store in the lot in a few minutes. That will tell you if it's putting out rated current. And yes, the regulator is in the alt, so that will be tested at the same time.

 

I got the alternator tested at O'Reily's this morning, and it tested perfect for volts and amps. I have started tracking wires for rub throughs and have not had any luck. Does the PCM control the idiot light or something else. It seems to be charging fine, I just hate the darned light. I am at a loss. Any other ideas. Thanks

 

Did a search on the forum on the subject and found one guy with your problem, had a rubbed wire on the main wire harness that goes over the top of the driver's side valve cover.. (Read afew posts where this will also affect injector/glow plugs..) Anyway take a mirror and look under the main harness for rubbing... I copied the following:

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Went thru this myself not long ago, Battery light started flashing, checked alternator,checked good but batteries eventually went down, this was in Laramie wyoming, put in new alternator and two new batteries, truck went all the way to Colorado, started flashing again, pulled in and checked the alternator, no output again, parts store gave me a new Alternator since mine had a warrenty, and recharged the batteries. This time made it to Amarillo, Texas and once again, flashing light, dead batteries, etc.
Put it in the dealer, the found a broken wire (just one) in the wiring harness that runs over to the computers across the top of the drive side bank. They charged me 540.00 buck to fix that wire( it was Christmas Eve). Got it back to Houston and guess what, same thing again. Finally I replaced that wiring harness segment and have never had another problem. I wish you well, these kind of problems are why I have gray hair now. But I still love this truck.