I looked around, but I couldn't really find an answer to this. I'm installing a mechanical boost gauge and using a fuse tap to power it. I figured the cigarette lighter fuse would be a good place since there's no power when the car is off. The problem is, the gauge is staying lit when the car is off. What am I missing?

 

Cigarette lighter is a 12v constant if I'm not mistaken. I've used it as a source before as well but I had a switch in line to cut the power. I would look up a diagram for an accessory wire that cuts on when the key is turned.

 

That is weird, it should be ignition on power only.
You're certain you tapped into the 15A F32 fuse.
I know I've caught myself messing that up.

I would just try another one, like the radio or something else non essential like that.

 

Yeah, I thought it was weird, myself! I got the right fuse, the cig lighter wasn't working when I pulled it. I'll be getting back at it around 8:00am EST.

 

Ok, I went back out and made sure I was using the f32cig fuse and I certainly was. I tried using the stereo fuse and..............the damn light still stays on with the ignition off and keys out! What the hell?

 

Both the cigarette lighter and radio can be used without the keys being on if I'm not mistaken. Most cigarette lighter sockets I've ever used in cars worked this way but I haven't tested the mini. The radio I am positive though that it can be turned on with the car off since I use this feature regularly. This leads me to believe that if you tapped those wires, it will stay on as you described. Could be completely wrong or missing something here, so feel free to correct me if I'm being misleading.

 

In my R53 my cig lighter loses power when the car is off, HOWEVER, you're right about the radio, that can be used with the keys out of the ignition......I forgot about that.

 

Ah, alright. I'm sure someone will chime in on where they tapped in since there seem to be a bunch of people with them. You could also try to look for an accessory wire and check with a meter for key off/on voltage to find a good one.

 

I just looked at mine, I've tapped at F39 for the switched power relay for all my gauges, honestly though, it's been so long since I did it, I don't remember why it was there, and if that's not something else, but it's the only tap in my fuse block, and I can't think of any reason to tap at the block that was constant hot.
Sorry I can't be more precise.

If that's not it, and no-one else can help, just figure out which side of the block is hot and start testing fuses with a test light, that may be what I did to figure it out.

 

Alright, thanks, I appreciate your help. I'll try f39 tomorrow and see what happens.