Voltage to run/accessory fuses without the key on?

[chuckludwig]

Perhaps I am fundamentally misunderstanding something, so perhaps someone can chime in:

I'm trying to wire something into my fuse box (using a fuse tap) that should only be on when the key is switched accessory or run. It was my understanding that the F5 or F6 fuse would do the trick BUT when I test voltage to either of these terminals, I am getting 9-10 volts. The F1 and F2 are getting the full 12v.

My fear is somewhere in the rats nest of wiring the previous owner did, they somehow have something giving constant power (or a wire is worn out somewhere), but before I go hunting for a short, I wanted to check in with you smart folks and see if perhaps I'm simply thinking about this wrong and seeing 9v or whatever with the key off is normal.

Thanks in advance!

 

[Hemikiller]

Fuses 1 & 2 are always hot. Fuse 5 & 6 are switched and should not have voltage without the key in Acc or ON/Run. They also share the same buss, so power to one means power to the other. Since #6 is the radio fuse, that's a likely candidate to be butchered. However, start with pulling both fuses and probing the inner terminals that are attached to the buss. You should not have power there with the key off. If you do, then you have power coming in through 297A, which comes from the ignition switch.

 

[chuckludwig]

Yeah that’s what I reckoned. I was hoping there was some quirky ford thing going on haha. Well, guess it means I’m spending the day hunting down electrical gremlins. Thanks for your help. If I figure it out I will post here for future travelers.

 

[chuckludwig]

Update: So I pulled the F6 fuse, and that eliminated the voltage going to the bus, which suggests that somewhere south of the fuse box something is getting some + volts it shouldn't be. If I'm correct that circuit is for the turn signals, washer pump, radio, and backup lights. I guess the next move is to start disconnecting things and seeing if the problem goes away at any of them.

 

[giantpune]

Sounds like somebody grounded some aftermarket LED headlights wrong or something.

 

[chuckludwig]

Well, I hope not since I wired the headlights! Haha. But no, the culprit actually seems to be in the ignition switch. Which honestly is great news.

It seems that when you turn it to accessory, some times that stays stuck on, so it continues to supply voltage to the ACC terminals. I'm not sure how that switch works, so I will have to take a look.

When the switch isn't being fiddily, I'm still seeing ~250mV which I'm guessing is not an issue, as I think that is normal?

Anyone have suggestions on fixing the switch? Is it easier to service or simply replace?