Flashing battery on dash

No. I have a 19 yo E150 and have never had an charging system problem.

Alternators can fail at any time, and more so with age. Take the alternator to a auto parts place and ask them to check it out. They will tell you if it is defective or not. Auto Zone or Advance auto parts are 2 of the possible places.

Is it doing this when you are driving with your generator running? I ask because mine flashes under those circumstances. If I turn the dash air on it must create enough of a draw because the flashing stops. So in my case, I think it is overcharging rather than undercharging.

Jaye(Mn)

I was running the generator while driving. The rig had been plugged into my home via an extension cord, which would have resulted in fully charged batteries. In checking the voltage, it read 14+ on both main and aux. while driving. I would hope an alternator would still be good at 30,000 miles.

Sounds like mine. (2007 Georgetown, F53 chassis) I have asked on forums a couple of times about this with no firm answers. I believe there may be some feedback of some sort, but am no electrical guru. Bottom line...if your lights not flashing when the genny isn't running, I think your alt is fine.

Jaye(Mn)

Mnflyboy wrote:
So in my case, I think it is overcharging rather than undercharging.

You REALLY should find out which it is.

My C with a Ford E450 had the alternator fail at 9 years and 50K miles.

The battery meter on the dash is USELESS. The battery will get low enough that the engine won't run BEFORE the needle moves enough so that you will notice.

My plug-in voltage monitor saved me. It suddenly started showing less than 13 volts when moving and less than 12.5 at idle and with the fan on high.

Dont really have to remove the alternator to test it. With a simple volt meter measure across the battery with engine off, will read around 13.5VDC. Now start the engine and take a second reading. 14.5VDC or higher at idle indicates the alternator is working.

Does your generator charge the start battery as well as house batteries?
Did it keep flashing the light with the generator off?
Did the start battery go low or dead? Because if you ran a significant amount of time with no alternator it would pull down your start battery resulting in the engine dying or not re starting.
No it is not common to lose an alternator at 30kmi so I'd look to something simpler perhaps related to running the generator.

Let the house battery discharge a bit and take it for a drive with no generator etc. If the light returns to normal I think all is well. Run the dash air conditioner and headlights during the test.

I believe my solar creates the same issue periodically on my F150. I also have a gauge that was dropping a couple Summers ago and at that point I did need a new alternator at about 14 years and 180,000 miles.

Also you can measure battery voltage is about 13.5 to 14.5 and call it good.

donn0128 wrote:
measure across the battery with engine off, will read around 13.5VDC. Now start the engine and take a second reading. 14.5VDC or higher at idle indicates the alternator is working.

Actually you missed the mark with both of those numbers.

The bare battery won't read near that high unless it's been under charge real recently. 12.6-12.8 is more common.

And most modern charging systems rarely go above about 13.8 unless there is a serious need for current at the time (like a drained battery).