Clevelandkid

Cheers to all. New on this forum and have heard about it for a few years and decided to join as I'm having a slight problem with My 2010 F150.

I purchased a used 2010 F150 XLT in April 2014. Its a nice clean truck with 61,292 miles when purchased. It now has only 64,300 miles. It has the 4.6L 3V engine and I'm currently on my 3 rd battery. I tried to start it yesterday after setting for a bout a week. Would not crank. Volt meter read 10V across the battery. Put my battery charger on for 10 minutes and it started right up. The battery was replace last fall and has worked flawlessly since then. Now all of a sudden the same problem is occurring again. All connections are clean but from what I have read on the net it could be an intermittent charging problem with the alternator.
Any help or suggestions would be appreciated. Thankx.

Mod (Ret.)

Have the alternator checked. Most parts stores will do it for free.

Clevelandkid

Thankx Bucko that was my next thought. These alternators have built in voltage regulators and I have been told they sometimes work intermittently when they start to go bad. Also there is a grounding issue where they bolt to the engine that can make them go bad. I'll swing buy my local Auto Zone and have them test it.

santa06

Check the miliamp load on battery after car sits for 15 minutes.

Should be around 80-120.

Feathermerchant

Also put a voltmeter on the battery with engine off then with it on. Static fully charged it should be about 12.5V but with engine idling 13.5 to 14 or so. It should not drop when you turn the headlights on. If you are really cheap, try replacing the brushes. They are about the only wear item.

Clevelandkid

Ok thankx guys I will try that check. But still can't figure out why it took 8 months for this problem to appear again. I have replaced the battery twice since purchasing the truck with new batteries. The last one had 2 bad cells. They were new Motorcraft batteries. The one thats in there now was made in 6/15. I suspected an open circuit but took it to a shop and they didn't find any. So thats why I suspected the alternator is intermittently charging.

Feathermerchant

Intermittent alternator - I have repaired two of these on different cars. They were both a rotted connection to the crimp on terminal at the alternator. So start looking at that connection for signs of heat. Darkened or cracked or unusually stiff insulation are good indications of heat stress. In both cases I replaced the connector and soldered it on.