No start, no power, not sure

[Mesozoic]

Today I took some time off of work to go title and register my '00 Mounty (bought it last Thursday). Parked at the title agency and when I came out to return to work, everything was dead. The THEFT light was blinking slowly, but the voltmeter was indicating full low. I called a coworker and we jumpstarted it, let it run for a while, voltmeter was indicating somewhere in the middle of its range, and eventually the truck made it back to the office.

Before turning the engine off, I measured 12.8V at the battery terminals. Turning the engine off, I also saw 12.8V at the battery terminals. So... there may be an alternator issue, possibly, but I decided to charge the battery for about 5 hours and return later.

So, I returned 5 hours later and the battery is looking ok in terms of voltage. Tried to start it, and same behavior as before: THEFT light blinking slowly, full low indicated on voltmeter, multimeter reading about 13V at the battery terminals (even while turning the ignition switch to crank). I then tried to jumpstart it with my Bronco, running an Optima deep cycle and 3G 140A alternator. No dice, voltage at the battery terminals reading 14.1V, but nothing inside the Mounty, no lights, nothing.

I checked underneath the Mounty to see if maybe the starter power cables had been cut or damaged or loose, but everything looks fine. I followed the Ford procedures found on this website, including swapping the starter motor relay with the blower motor relay and I verified that pin 85 of the starter motor relay is getting 13V during key on. I probed every single fuse in the internal fuse panel and the power distribution box and everything is looking ok.

Not sure where to look next. I was starting to think that maybe I had a power diode problem of some kind, but that's just a guess. Anyone have more experience than me with a 2nd gen?

 

[1998Exp]

You checked the starter cable, but how about the battery cables (including the negative one)? They like to rot inside the insulation.

 

[XLTrunner]

Checking the battery cables is a first step. Any clue as to how old the battery is? I've had instances where the voltage across the terminals looked good, but battery wouldn't crank the vehicle. Even taken them to an auto parts store where they were declared "good"...only to learn later that a replacement battery solved the problem. Can you swap the battery from your Bronco and see if the Mounty starts?

 

[Mesozoic]

Checking the battery cables is a first step. Any clue as to how old the battery is? I've had instances where the voltage across the terminals looked good, but battery wouldn't crank the vehicle. Even taken them to an auto parts store where they were declared "good"...only to learn later that a replacement battery solved the problem. Can you swap the battery from your Bronco and see if the Mounty starts?

The battery is an Interstate 850 CCA unit, my friend with a transmission shop nearby tested it and it pulled 805 CCA on the 1st attempt, 736 CCA on the 2nd, so not sure if it's ok or not... it's dated 10/2013, so not super old, but maybe.

I haven't performed a battery swap yet, I try to leave my Bronco alone since it's EFI and disconnecting the battery will force it to reset the Keep Alive Memory and tune for the engine, but I will probably find a spare laying around my shop next. The battery cables look ok, although there's a minor amount of corrosion due to the lack of corrosion inhibitor on the connections to the terminals. I have very nice new terminals in a box, might just go ahead and swap them in.

 

[Mesozoic]

So the issue turns out to be corroded wires, for sure!

I removed the battery terminals and replaced them with some nice Raptor pieces, but I wire brushed the wire strands until they were clean and then finished them off with 150 psi of compressed air. Once the terminals were assembled I use NCP-2 to cover up any exposed copper and done... Mounty is back in action!

 

[XLTrunner]

Glad to hear you found the cause...and, it was a minor fix. Good reminder for everyone to pay attention to the condition of their battery cables. Thanks for posting your results for the sake of others who might encounter the same problem and need some help.

 

[Mesozoic]

Additionally, this serves as a warning for those that live in dry climates, like southern Arizona, are not exempt from corrosion issues.

Also, according to my mechanic friend, AGM batteries are less prone to exhibiting this issue because they are fully sealed and the likelihood of acid fumes seeping out from the case is far less.

 

[funfool]

yay! glad it was a simple fix.
I have found that once the cables get all the green gunky corrosion on the ends, it is already inside the cable.
So you clean the ends and in a few weeks or months, it comes back and you have the same problem again.
It would probably be best to replace the cables at the next convenient time, or wait 2 months and at a inconvenient time, deal with it again

 

[Mesozoic]

yay! glad it was a simple fix.
I have found that once the cables get all the green gunky corrosion on the ends, it is already inside the cable.
So you clean the ends and in a few weeks or months, it comes back and you have the same problem again.
It would probably be best to replace the cables at the next convenient time, or wait 2 months and at a inconvenient time, deal with it again

Yeah, I am going to have to replace the ground cable/negative battery cable, for sure. It's functioning at the moment, but you're right, I think the corrosion was pervasive and the damage has been done. I might also upgrade to an AGM battery at that point. A local shop here sells custom made battery cables so it shouldn't be too much of a hassle.