I have a 2003 F350 with the 7.3. We were driving around looking at homes this weekend and the battery light on the dash came on. A few minutes later it went out. Then a short time later came back on, then off again. This happened maybe a half dozen times, then went off and has not come back on again.

Supposedly, when I purchased the truck in April of this year the seller said he had just replaced both batteries. Could be a bad battery. Seems like if it was the alternator it would come on and stay on.

Anyone have any ideas what could cause this.

 

I had an intermittent battery light on mine that would come on at higher rpm and then go off. Turned out one of the brushes in the alternator was very worn. You most likely have a 6g alternator which is a little more involved to check the condition of the brushes than the 3G that was more common on the gas SDs.

You could get the batteries load tested to see if they are in good shape. However they may not be the problem.

 

Yup! your alternator is going out. it requires a certain voltage from alternator to keep the light off. (I know its very basic explination but its right) and you are most likely dipping below that threshold and above. it will fail completely before you know it.

 

OK Thank you. Looks like I will need to have it rebuilt.

 

I was wondering why I would have this problem on Saturday and then nothing since. If the alternator is going out, would I see this more frequently?

 

+1 for the alternator. That's what mine was doing before I replaced it.

 

there can be many factors that could have caused this on a particular day. humidity, did you just wash your motor. did you run the alternator up in revs higher than what it does from day to day. mine went out after towing a rather large trailer. we would constantly have to down shift and motor was seeing some higher than normal revs. next day light was on. day after that it was not. then it failed completely.


trust me and others on here its on its way out.

 

OK, I believe you. Just wanted to be sure.

Thanks for the advice.

 

So on Thursday July 2nd, I replaced the alternator. Everything seemed to be working good. Drove the truck once on Friday for a few minutes then it sat until today, Tuesday July 7th. When I started the truck the battery light came on and only when the RPM's increased did the light dim, until I got to work then the light finally went out. Looks like I will be replacing at least one of my batteries. Strange how these seem to go hand in hand (alternator and battery).

 

Where did you get the alternator from?

 

Our local Auto Electric Shop. They are very reliable. The truck has been sitting, so the alternator was not in play unless it is drawing energy from the batteries while it sits. The batteries did finally build up enough of a charge in them on the drive into work today to turn the light out.

 

OK, here is an update. I spoke to the shop I purchased the alternator from yesterday morning.
They were very concerned about the operation and offered to test the alternator and my old one to ensure that I actually needed the new one. They also said they would order a backup should the one they sold me turn out to be bad along with a new connector for the control circuit.
We discussed the symptoms and one thing didn't make sense. The battery light came on but then would dim when the RPM's would increase but not proportionately. They indicated that this was not normal and the light should be on or off. They recommended I double check the connections.
So before I left the work parking lot I popped the hood and pulled on the control connector. It popped right off. I pushed it back down and thought I had now made a good connection but when I pulled on it again, it came off easily. After some effort I finally heard the distinctive snap and it was fully seated.
Started the truck and no light. No light on the way home last night and no light this morning. Boy did I feel like an idiot. I called Mark at the shop last night and told him what I had done, he indicated that wasn't that unusual. But said to monitor the condition and should it return, to bring it down and they would take a look at it. Seems like the snap type connectors can go bad and not create a good connection. There must be an issue as they stock the replacement connectors.
This is why I purchase my electrical parts from a reputable automotive electrical shop. They rebuilt my thruster motor (like a starter motor) on my boat a couple of years ago for only a fraction of a new one. New motor $900, rebuild $125. But that is what they do.
For anyone in the Everett, Washington area. I highly recommend G&H Auto Electric. Mark is fantastic to work with and their prices are better than most of the chains. They had quoted me $169 with tax but when it came in the price was $165 including the tax. Nice to have honest people to work with.
I also wanted to thank those here that responded to my post. Appreciate all your help.