Battery for Frunk Release to store in bumper

[SnBGC]

oh, I see you got the battery junction box. (thanks!)

The LVB is up closer to the windshield, but the LVB jump points are down lower as shown in the diagrams (so just the lower end of the back #2 ground cable, and the + jumper post).

It looks like the BJB is just the regular under the hood fuse box. That kind of makes sense, because there are so many fuses referenced to the BJB now. The only odd thing is that the fuse numbers from these Ford diagrams do not seem to match the fuse numbers in the MME supplementary manual.

So those two 5A fuses probably are the two I found in the fuse box listing of the supplementary manual.

Arrgg, I need to pull those panels again, and see how difficult it is to access those fuse blocks. I wish it was 40 degrees, sunny, but 20F and windy today! (and, some work now, only semi-retired )

I think you are right.....the on board LVB is up higher. (too many vehicles.....too little time to remember where all the stuff is....)

I borrowed a Fluke meter and checked those wire again and now I get 6.5 mV so I must have had my meter at home set to the wrong scale. That is unlike me to mistake something like that.....I will check my meter when I get home. I usually break out my PowerProbe because I find that more useful when dealing with automotive electronics but I didn't do that last night.

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[breeves002]

The hood latch release is called the GFM (generic function module) Ford vehicles have had these for years for various functions.

When you energize the GFM from the trunk release, the module turns on (assuming dead 12v battery) and will then check its supply voltage, see it is below the set threshold, and release both hood latches. This all happens very quickly.

Kind of re-iterating what was already said but thats a basic system operation from a networked point of view.

 

[SnBGC]

The hood latch release is called the GFM (generic function module) Ford vehicles have had these for years for various functions.

When you energize the GFM from the trunk release, the module turns on (assuming dead 12v battery) and will then check its supply voltage, see it is below the set threshold, and release both hood latches. This all happens very quickly.

Kind of re-iterating what was already said but thats a basic system operation from a networked point of view.

Cool. Sounds like a much better method then trying to use a self latching relay that is somehow set when the voltage is low. The GFM would be nearly foolproof when used like you describe.

 

[generaltso]

Cool. Sounds like a much better method then trying to use a self latching relay that is somehow set when the voltage is low. The GFM would be nearly foolproof when used like you describe.

Of course, it really makes you wonder why they went through all of this trouble instead of just hiding a manual key cylinder somewhere on a door.

 

[CHeil402]

Of course, it really makes you wonder why they went through all of this trouble instead of just hiding a manual key cylinder somewhere on a door.

Because that's not "cool"... and partly because it saved the cost of having to add the hardware to play nice with the door opening push mechanisms they have and they don't have to cut individual unique physical keys.

...and because it will never fail, obviously.

 

[breeves002]

Cool. Sounds like a much better method then trying to use a self latching relay that is somehow set when the voltage is low. The GFM would be nearly foolproof when used like you describe.

Since it is a networked module it has some logic so it is able to do simple things like compare voltages. Having a ridiculous amount of modules has its perks as long as they don't break.

Because that's not "cool"... and partly because it saved the cost of having to add the hardware to play nice with the door opening push mechanisms they have and they don't have to cut individual unique physical keys.

...and because it will never fail, obviously.

I liked the key hole in my Lincoln Continental. It was noticeable but honestly not very obvious. I used it once to try it then never used it again. Those doors had such a nice latching sound.

 

[eltonlin]

Of course, it really makes you wonder why they went through all of this trouble instead of just hiding a manual key cylinder somewhere on a door.

Not. Aero.

 

[buffasnow]

Not. Aero.

I could live with a keyed lock on the trunk.

 

[SnBGC]

Of course, it really makes you wonder why they went through all of this trouble instead of just hiding a manual key cylinder somewhere on a door.

Oh my gosh YES!
It would have been sooooo much easier and better to just put a lock cylinder in the liftgate and some 12v terminal blocks back there.

 

[generaltso]

Oh my gosh YES!
It would have been sooooo much easier and better to just put a lock cylinder in the liftgate and some 12v terminal blocks back there.

Something they can save for their first model year refresh I guess.

 

[CaptainET]

would a key lock inside charger door that opens frunk be possible?

 

[louibluey]

Okay, so this is interesting, each of those two small 5A fuses is used to power a separate relay (in the aux relay box), Front trunk release relay 1 and 2. According to this diagram, their only purpose is to break or make both of the power and ground wires (presumably Amps) that operate the Front Trunk Door Latch.

The Front Trunk Door Latch is probably the actual electromechanical component at the latch with some kind of solenoid coil in it that needs Amps to operate (the actual "actuator").

Those two relays might be (?) more of an "enable" as controlled by Body control module. That is, if the Front Trunk release relay wants to open the Frunk, it can only do so if not locked out by the two Front Trunk release relays.

Note that the connector on the Front Trunk Release Relay (clearly not just a relay, but a module, as are other blocks) is C2435. In the first diagram we began with, there are pins 2-8 which include wiring between the Front Trunk Release Relay and the networked GFM (Front Trunk Release Module with CAN bus). Now, in this diagram, the same C2435 also includes pins 9 and 10 which are the actual high current paths to actually provide "PWR" and "GND" to the Front Trunk Door Latch (upper right, this drawing). Possibly that power control is by power semiconductors, not actually by mechanical relay contacts. Also, as noted earlier, anytime a relay or solenoid coil is controlled by a power transistor or the like (e.g. MOSFET), there will be a reverse diode across the coil to dissipate energy stored in the coil when it turns off (the L di/dt voltage for the many EEs on this forum). The reason that detail is important is it might explain why Ford says we have to observe the polarity of the Red and Black bumper wires when using an external source. Otherwise, the current would just flow by the solenoid through the shunt diode (if the external bumper power supply or battery is connected incorrectly), which might also explain in part, those two 20A fuses at the bumper.)

 

[louibluey]

would a key lock inside charger door that opens frunk be possible?

There are so many great options like that, which are possible.

For example, what about another small aux LVB battery, say about 1/2 size of the existing 35 Ah battery mounted under the hood next to the main LVB, with a remote button somewhere. That "aux" LVB could be momentarily connected to the main LVB (relay, power semiconductor, etc.) to attempt a remote LVB boost / start. The aux LVB could be on a trickle charge from the main LVB (reverse current flow prevented) so the little aux battery is always ready for an emergency start attempt. Heck if Ford implemented something like an aux 12V LVB, you could try an internal "jump start" from the smartphone App!

 

[louibluey]

Where is the Front Trunk Release Relay? with its connector C2435?

Found the Aux relay box, near the firewall, windshield.

Here is the Latch connector C1846:

 

[Hplbiking]

Someone correct me if I'm wrong - Is the Frunk a pull, (non electric) release? I remember having to pull it twice to open the frunk.

I was thinking the same thing. I thought the process was apply power to the small door in the front to get enough power to open the car and then pull (twice) the hood release.

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