[jasongoss]

I have a thought and wanted to run it by the experts (if your reading this consider yourself a semi expert) From the factory the up-fitter switches only have power when the vehicle is running or the key is in the ignition. I have the dual battery set up.
I was kicking around installing a switch for when van was off I could still power the switches from the batteries. From what I have read the fuse panel is located in very close proximity to the batteries.
My thought was install a switch that would either get power from "A" OR "B"- I believe, correct me if I am mistaken, that is a double pole double throw switch.
I like the look of the marine switches (image below) that let you choose but I did not know what would happen if the panel was accidentally powered by both sources. So it sounds like the DPST switch is the way to go- any thoughts for or against this idea?

 

[jasongoss]

Correction. It looks as though I could use a double pole single throw switch. DPST

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[RandomJoe]

No. Double-pole single-throw means there's two sets of contacts and both of them make or both break.

You want a single-POLE double-THROW which switches a single center connection between the other two terminals. It only connects to one or the other but never both. (A double-pole double-throw also works, it'd just have an extra set of contacts that would be unused.)

You also wouldn't want the one you linked to as it has the "1+2" position which means both are connected at the same time. These are sometimes called "make before break" switches, meaning as you change position the new connection is made before the old one is broken. For a boat or RV with multiple power banks you want that so you never lose power. In your upfitter switch scenario you do NOT want to do that.

You want a switch that's "break before make" meaning it disconnects the previous connection before making the new one. Most double-throw switches do this, especially the ones with a center-off position.


One caveat: You need to make sure you know how Ford is controlling the upfitter switches. The majority of items in the Transit are low-side controlled, meaning the computer is switching the ground connection. Since the upfitter switches die instantly when the key goes off they may well just be getting powered from some 12V switched-hot rail - but need to be sure!


Hope that helps, probably clear as mud...

 

[jasongoss]

Thank you the break before make is very clear. I will start searching for the spdt switch and get the multimeter out. Thanks for the note.

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[bicyclist]

Those switches are supplied by a 3A fuse F12 from an ignition-on source. Each then operates a relay, R1-4. The relays are supplied by 20A fuses F4-8 in the aux fuse panel. So, you need to determine whether power to those 20A fuses is constant (probably is) and then provide a source of power to the upfitter switches through another switch.

This info comes from the BEMM P126.

It'd probably make more sense to wire your loads from the CCPs if you want always on power.

 

[Damaskinos_of_Athens]

.
Sounds like a good suggestion for an enhancement.

Each upfitter switch should have a button that controls always on or just when running.

Ford wants happy customers so the more you ask the more likely you are to get - especially if it is so simple.

.

 

[danketchpel]

Those switches are supplied by a 3A fuse F12 from an ignition-on source. Each then operates a relay, R1-4. The relays are supplied by 20A fuses F4-8 in the aux fuse panel. So, you need to determine whether power to those 20A fuses is constant (probably is) and then provide a source of power to the upfitter switches through another switch.

This info comes from the BEMM P126.

It'd probably make more sense to wire your loads from the CCPs if you want always on power.

I'd sure like to know the answer to that, is the power to the relays constant?

I want my upfitter switches to have a constant power source and I'll flip them on/off as needed.

I might have to do some wiring mods......, please post back what's found in this regard.

Thanks ahead of time.

 

[bicyclist]

I'd sure like to know the answer to that, is the power to the relays constant?

It's quite likely that the power to the relays is constant and only the the power to the switches themselves is switched by the ignition. Since the relays are controlled by the switches, when the ignition is turned off, there will be no control current supplied to the relays and they'll drop, so no need to cut off the voltage supplied to the relays. Make sense?

Somebody posted a link to a wiring diagram somewhere. Find the link and you'll have your answer.

 

[jasongoss]

I will search for that. If I find I will repost.

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