In DTR's vid below, at about the 5:40 mark, he's describing FICM voltage. He cites 45 as the minimum healthy voltage, then adds, "for trucks, vans can go lower, because of the long run." He repeats it, but never says how low vans can go. I assume that the "long run" he refers to is the cabling to the battery location, since they aren't mounted in the engine compartment like a truck. Which would explain why he doesn't offer a low value for vans - the distance to the batteries varies with different van body configurations.

So, what do y'all think that low range should be? I ask because I have two cutaways and both exhibit low FICM main voltage. I already swapped in a new FICM for one bus, and it did improve the voltage significantly. But now, the second has the same problem - or maybe neither of them did? It displayed 42V at start up today, in 30 degree temps. But, maybe 42d is just fine for a cutaway van?

 

PCED says operating range of 40-52 Volts. Based on a complete lack of experience I have nothing further to add!

 

Who/what is PCED?

 

Powertrain Control and Emissions Diagnosis manual (no commas, lol)

 

In my opinion, for a good running FICM, it should not go below 48 for more than a few seconds, other than during start, which I didn't monitor. So if yours is going low like that, I would say there is something not going too well with it. If you swap FICM and it is still low, then something else needs to be looked into.

 

I recently had the same experience on my ‘04 X. I noticed on my SCT X4 tuner at start my ficm internal voltage started at 38 and would build slowly to 46 to 48 vdc never reaching a solid 48vdc. The X ran and started fine but the ficm was going to die a slow death along with my injectors. The injector coils are designed to operate at 48vdc. In electronic speak E=I x R where E is the input voltage, I is the current and R is the coil resistance. Therefore, if you have a lower input voltage, the current will increase producing more heat to the point where the injectors will eventually fail. I sent my ficm off and had it repaired. I now have a solid 48 to 48.5 vdc. I was told by the repair facility that long starter cycles (more than 5 seconds each) is the primary cause of ficm failures.

The other device that can cause a similar no start or low internal ficm voltage is the 70amp ficm power relay. Over time the relay contacts become burnt and or pitted and do not make full contact. Ask me how I know.

Ed

 

Once this one warms up, it stays around 48v constantly. Long story, but this bus has what I'm now affectionately calling a "burglar alarm," since that's easier that figuring out why the key doesn't work. All those gyrations prior to lift off - hood, battery box, hot wire, starter wire, wind, rain - I keep forgetting to see what initial voltage is at KOEO. By the times I have everything closed up, then remembered to pull the phone out, I saw that 42d low, one time, and it rose from there. Which is basically what the other bus was doing. I've not driven that one now in a bit and forget what it says at KOEO, but after swapping in the known-good FICM, in the same scenarios as above, its always been at least 46 driving.

So, what is DTR trying to tell us? I think most people find him credible, and it sounds like the typical fact-based disclaimers he's constantly throwing in that make him sound credible to me. It was important enough to him that we know.

Maybe the "long run" is the FICM itself? Rather than on top of the valve cover like the Fseries, it's on the driver side apron? easily a foot or more further from the engine, and in my config, even further away from the batteries under the rear passenger side. Can cable distances have such affects? Is it worse because the FICM gets colder/stays colder longer not being on the engine? In my case, would the block heater keeping it warm, help this?

You know I'll never figure out those answers, or even know whether y'all's answers are right. But, maybe there's a rare consensus, and I can benefit.

 

Longer wiring will mean more voltage drop provided that the wire size stays the same. A drop in V+ supply to the FICM will make the FICM have to work harder and it would not surprise me to see a lower FICM voltage.

The FICM voltage getting lower means that the FICM will need to be repaired at some point.

 

That makes sense. Anyone think of anything else that could be a "long run"? If that's the best guess, and if voltage getting lower means a repair at some point, what is DTR trying to disclaim? It sounds to me, the way that statement comes right after he says trucks can go down to 45v and be OK, that he believes vans can go lower and still be OK. I don't know what other point he could be making.

You're telling me the cabling will have an effect; he might be saying that effect is OK. You describe "getting lower," which would seem like a warning sign, I'm wondering DTR is describing a lower voltage that was "always there," and therefore not a sign of anything.

The way FICM voltage jumps around all the time anyway could be what he means. That if your van jumps lower than 45 for a moment, it OK, but if it sits lower for a minute or stays lower, it's not. I don't know. I just want to know what I should be looking for. DTR means something.

 

Heat is the one that fails electronics, besides vibration. Mounting it close to the engine makes both worse.
If your is mounted far away, it's better. Less vibration, less heat.
That said, if add another wire to help with the current, I would. Usually, if you add the positive, it would help to add the ground wire and make sure your ground is good. DTR said it's ok, can mean it'll last a long while, but who know how long that is, and whether you want a "very" long while or just a long while :-)
Furthermore, it maybe ok at 45 volt, but other factors may make it worse. For example, for system that hovers at 45v, it may means much lower cranking voltage. I don't say yours is like that. I just want to say if understand the nature of it, then we'll understand DTR better and the FICM better.

 

There are a lot of engine control electronics that are mounted directly on the engine, so the reliability would be more of about a particular design rather than generically if it's on the engine or not. Maybe 12 years ago Gearloose was all over the various Ford diesel forums promoting moving the FICM off the engine, like the vans, but he never did it himself, and neither did anyone else. It would take a Ford tech with experience to say if the mounting location makes a difference; the Van has a lower failure rate than pickups.

About 5 years ago Rick (HT32BSX115) brought up that most equipment like the FICM is a switch mode supply, and more likely just shut down if the voltage is too low, or too high. And that if it's designed properly, the input voltage will not decrease the output voltage. He asked, why would any company (Siemens) design an electronic device like this that would fail due to low voltage intentionally, or to that effect. He has an EE, so I'd trust what he says. A comment that blows the crap out of the larger alternator industry.

Of course, then there is always is the IF it's designed and spec'd correctly.

After he posted that, when I had my 110a alternator installed for testing starting and recharging of the different alternators, I looked at didn't see the voltage output really drop while the 110a was full out but voltage output was still muted by the glowplugs. Short study, easy when you are charging the batteries each and every overnight for the next day's alternator tests.

The fact is, even though I've asked a number of times, I don't know that we have a solid handle on what causes the FICMs to fail, other than those that will gladly sell you an alternator, but that really isn't the major voltage concern for me, its during key-on, and starter engagement.

What I can say is there was a post a long time ago from m-chan68 who said the 7 screw FICMs do not fail as much as the 4 screws.

 

The little that I can add to all of these more knowledgeable people is a general agreement that as the quintessential innocent by-stander, it does seem to me that FICM failures are not quite understood. I say that not just because I'm too ignorant to understand, but also from all the people I see selling repair services. It's like the market (long ago) accepted that FICM failure is here to stay, nothing to be done about it, move on to commoditizing the repair and replacement.

 

One of the FICM I have is from an e series and it has 48 volts. Also, both FICM that I opened up has hair line cracks on some components solder, which I melted again.
They have capacitors that are prone to heat and vibration. The deal with capacitors is that they stabilize and also provide power for in between peaks of voltage (in millisecond) . So if they don't work well, under a scope, voltage are not smooth out. You don't see a disconnect due to parallel connections nature of many capacitors. I miss tinkering with electronic. Those EE days. Hopefully I will get back to my sensor Android head unit project soon, maybe in 6 months or less.

 

The use of whetted lead-free solder has been the demise of many circuit boards used in the auto world.

 

I agree with this. I only use leaded solder mainly due to the fact that it requires lower temps. When I try to desolder components without leaded solder I feel like I'm applying tons of unnecessary heat to them. Not to mention leaded solder would probably be less prone to cold solder joints when repaired by hand. Also the most demanding situations for these electronics is during long cranks when voltage drops and amperage skyrockets. I have a EE degree but also knew most of what I learned before I got my degree just tinkering in the garage as a kid or setting up CNC machines when I was 14 for my fathers highschool labs. College was sooo boring other than some of my advanced programing and electronics design courses.