SOLVED 2011 Explorer Battery Gremlin

[tawjganon]

Please help.
2011 Explorer XLT V6, named "Vader", with 179k miles. Engine runs amazing, shifts great, drives smooth like luxury with no issues. The problem is, if it sits unused for about 48+ hours it won't start. Sometimes it has absolutely no power, and sometimes it will do the startup procedures correctly, lights work, then when I turn the key it goes dark and the fuze panel under the hood starts a rapid clicking noise that doesn't stop.
After attempting diagnosing myself with 0 success, I took it to a shop and $220 later they said it has no issues, despite having to jump start it in order to drive it TO the shop. No warning lights, no codes, battery works great (its 5 months old), alternator works great, starter works great, and the draw when off is only 15 milliamps. Does anyone have any suggestions on where to go from here? I'm lost. Please help! Thanks!

SOLVED. Cleaning the ground strap/stud did not end up being the fix. The problem was the NEW battery from Ford had a "bad cell". Call it unlucky I guess, but Ford gave me a replacement under warranty and I have had 0 issues since. I even had the battery tested by the shop I took it to and they said it was fine. Maybe their machine doesn't check everything? Who knows. Let's put another 100k miles on this Explorer

 

[peterk9]

Welcome to the Forum.
When it won't start do you have lights and does the HVAC work along with accessory mode? Have you checked the engine bay fuse box to see which relay is clicking? #13 is the starter motor relay according to your manual.

Peter

 

[tawjganon]

Welcome to the Forum.
When it won't start do you have lights and does the HVAC work along with accessory mode? Have you checked the engine bay fuse box to see which relay is clicking? #13 is the starter motor relay according to your manual.

Peter

Thanks! So when its not completely dead, everything works as normal until I turn the key to start it. Lights, entertainment, heat, everything. Then the key turns and rapid fire clicking. I have traced the clicking to relays # 15, 66, and 88. New ones going in ASAP.
Another note, I found the ground strap under the battery tray seemed super green and corroded, as well as the stud its mounted to was SUPER rusty, especially since everything around it is nice clean metal with no rust at all. Took them off to clean and busted the stud. Cleaned the strap, got a new stud, took off paint, drilled a hole and installed new stud bolt. So far so good. Will have to wait a couple days to see if it sticks.

 

[Odrapnew]

I was going to say bad connection, which it sounds like you found.
My Mustang had similar issue this spring when the clamp end of the negative cable had a small break.
It would power everything but as soon as you tried to start it, dead. Wiggled the connector and 'rinse-repeat.'