Battery or Alternator or FICM?

[jluv]

2005 F250 6.0 w/ 120k miles
Interstate Megatron Batteries, about 18 months old

I've noticed over the past few months that it hasn't seemed to start as quickly as it used to. It wasn't real bad, just something I kinda picked up on. The voltage would be around 11.9v when it first started (which I have heard is normal because the glow plugs draw so much for the first minute or so), and then it would go to 12.8v-ish, and then once I started driving it would go to 13.6-14v. I was starting to think that the slightly slower start was in my head, and it always started, ... until yesterday.

It barely started last night. When it did, my voltage was very low. I have an aftermarket volt meter, and it would just flash "low voltage". I've seen this meter register as low as 10.5, so the voltage had to be even lower than that. Once it started, I kicked on the high idle function (keeps it around 1200 rpm), and the voltage climbed back to normal range. I noticed as I was driving, it would drop to 12.7v-ish at idle, but immediately climb back to 13.7k-ish as soon as the RPMS came back up. After driving for a while, the voltage would stay above 13v even at idle, which I figured is a good sign. But no - once it sits for a while, it starts all over.

I cannot identify anything that would be drawing any significant amount of power when the truck is off. I have a lot of accessories, but they are wired to acc (besides my alarm, which has been on the truck for 2 years).

I'm no expert on this stuff, but since the voltage climbs when I drive, I am tempted to think it's not the alternator. I plan to have the batteries tested today and maybe replaced, since they are under warranty.

But does this sound like it might be the alternator? Or worse, the FICM? I know both of those are known to take a dump on this model.

Sucks, because I am supposed to leave for a week-long camping trip to Colorado tomorrow morning. I absolutely cannot have this thing give me problems ion the mountain, as I'll be a long way from civilization.

Anyone have insight as to what this is? Thanks.

[Doug Hatton]

Considering I don't even know what FICM is, I'm probably of no help to you. Check the battery with the key off and see if it's steadily falling in voltage. My guess would be the voltage regulator/alternator, but it's purely a guess. The fact that the voltage is all over the place is what leads me to that conclusion.

[03shadowgreygt]

have the batteries checked. unless it runs rough cold its probably not the ficm, if it is cranking slower than normal you will probably notice the dash lights dimming and acting diff than normal. sounds like your alternator is charging, the glowplugs will be on up to 2 minutes so it won't charge much during that time. I have seen batteries last less than 18 months in diesels.

[jluv]

Considering I don't even know what FICM is, I'm probably of no help to you. Check the battery with the key off and see if it's steadily falling in voltage. My guess would be the voltage regulator/alternator, but it's purely a guess. The fact that the voltage is all over the place is what leads me to that conclusion.

The FICM is the "computer". They can go bad on these trucks, but I think they normall throw a code and trigger the CEL, but my CEL is not on, so I'm hoping it's not that.

I drove an hour to work (after it barely started this morning), and then had to go run an errand just now. It was off for maybe 30 minutes, and it started up fine. So the batteries are at least holding a charge for a little while. After driving for another 30 minutes or so on this errand, the voltage is holding strong at 13.9, even when I come to stop and the rpms drop.

My initial thought is that something is draining my batteries while the truck is off. I just don't know what it would be.

[jluv]

have the batteries checked. unless it runs rough cold its probably not the ficm, if it is cranking slower than normal you will probably notice the dash lights dimming and acting diff than normal. sounds like your alternator is charging, the glowplugs will be on up to 2 minutes so it won't charge much during that time. I have seen batteries last less than 18 months in diesels.

It runs rough when cold. Always has. I just thought that was a common thing with these.

I am really hoping it's just the batteries, or even the alternator. I can change those out myself very easily. How hard is it to change out the FICM, and are they crazy expensive? I hope that's not it.

[DON SVO]

sounds like batteries to me. the alternator is busting tail to hit the glow plugs, and then reload the batteries (which are already on the way out, more than likely)

[Baron Von Crowder]

had a similar issue when I had one dead battery. If I let it sit for more than a few hours it would need a jump. I actually had to go out at lunch and fire it up for a bit so that it would start at the end of the day. One replacement battery and all is good.

[FATHERFORD]

check the voltage on the FICM... should be 48v.

If it isn't you most likely have a bad FICM. There are a few companies that will rebuild and Improve on them. There is even a 58v upgrade.

[jluv]

check the voltage on the FICM... should be 48v.

If it isn't you most likely have a bad FICM. There are a few companies that will rebuild and Improve on them. There is even a 58v upgrade.

I have a multimeter, but don't know where exactly the FICM is or how to check the voltage there.

[jluv]

Batteries were shot, got free replacements. Alternator test shows it was going out as well. Just picked up a new 140 amp one from Ford and will be installing tonight.

Vacation saved!

Thanks for all of the replies

[Doug Hatton]

"I KNEW I was right!!!" says everyone that posted in this thread! LOL!

[DON SVO]

"I KNEW I was right!!!" says everyone that posted in this thread! LOL!

I said that WAAAAAAAAAAY before Jared even put up the latest post!