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I have been working on installing a dash cam into my car and ran across an unusual problem and I thought one of you might be able to help. I am installing a BlackVue DR900S-2CH dash cam with a BlackVue Power Magic Pro accessory for parking mode.
I am using fuse taps to connect the Power Magic Pro's battery (receives power when car turned off) and accessory (does not receive power when car turned off) connections to the car. The problem has been finding a fuse that is not active when the car is turned off. I opened the fuse panel near the front passengers right foot. When the car is turned off, I exit the vehicle, lock it and then wait about a minute. I open the car and start testing fuses using a tester with a light. Every single fuse in the panel is receiving power!
The unusual part is I can sit there in the passenger seat and try to open the sunroof. It will not open. However, the sunroof fuse in the panel is activating the light on the tester. I did some Internet reading and found people are writing some manufacturers allow power to fuses when a person is sitting in a seat, a door is open, or the key fob is within a certain proximity to the car.
My objective is for the Power Magic Pro (it has an on/off switch) to light up the power LED only when the switch is in the on position. The camera should be on when the car is turned on and remain on if the Power Magic Pro switch is in the on position or turn off if the switch is in the off position.
Currently, the Power Magic Pro LED light remains on regardless of whether the switch is in the on or off position. So, I uninstalled it and thought I would check to see if anyone else has had a similar challenge trying to install a dash cam, radar detector, etc.
A search will find several threads on this subject. The bottom line is that AFAIK the only switched fuse connection is on the fuse block in the trunk. There is a power off delay on several circuits. The easiest way to check a circuit is to connect a light to the fuse, turn off the ignition and wait a few minutes to see if the light goes out.
Some cars may be equipped with a 12v accessory socket in the front passenger foot well that is switched.
I am currently in the process of installing the Power Magic Pro paired with my Blackvue DR900s-2CH. The socket rear fuse is 458 and is a switched fuse. I am looking for a good constant fuse to tap in the rear trunk fuse box. I was wondering if you could shed some light on which fuse in the trunk you used for your constant power? Thanks!
Last edited by ryuan1688; Apr 10, 2020 at 12:47 PM.
Thanks for the responses! Currently trying to avoid using an OBD cable. I tried testing the fuses in the trunk for constant power using an analog multimeter, but I am having trouble detecting any power. I am also unable to detect power in the fuses in the passenger side fuse box so I think I am measuring it wrong. I believe it might have to do with where I am grounding the circuit having factory paint on it so its not bare metal.
Hey @Egonvdv and @ua549, I've looked through multiple threads before deciding to post. You guys are mainly referring to this thread two years ago: https://mbworld.org/forums/e-class-w...e-diagram.html. I was able to easily find the rear cigarette lighter switch because Egonvdv pointed it out in that thread. Regarding the fuse diagram that ua549 posted in that thread, he said that he didn't verify the information in the pdf was correct, so I did not want to rely on it. This current thread was the only thread I could find where the original poster was trying to hardwire a Power Magic Pro to the rear fuse box for constant power without using a BlackVue/Cellink battery pack. I was trying to prevent having to hardwire the constant power wire from the power magic pro to the passenger fuse box because the wire is not long enough.
Thanks though for the responses. I know that you both have been responding to most of the dashcam posts on this site and I appreciate the info you guys provided in them. I ordered an automotive circuit tester last night from home depot to test if I can find a constant power fuse in the rear. If that ends up failing, I'll have no choice but to buy the battey pack which I've been trying to avoid due to its price.
Last edited by ryuan1688; Apr 18, 2020 at 05:49 PM.
Beware that some switched circuits stay on for a few minutes after the ignition is switched off. The best way to test is to connect a light to the circuit, turn off the ignition and wait several minutes to see if the light goes off.
Check the driver side fuse block (assuming the W213 is similar to the C257.) It is access by popping off the side panel on the dash once you open the door. I hard wired a phone charger with a fuse tap to an open fuse slot and it was switched.
I know this is an old post but you mentioned if you just wanted to hardwire a dashcam to come on and off when the car is used its would be very simple, I'm trying to find those instructions, every single one I have found is the full hardwire like yours???
I know this is an old post but you mentioned if you just wanted to hardwire a dashcam to come on and off when the car is used its would be very simple, I'm trying to find those instructions, every single one I have found is the full hardwire like yours???
hardwire (piggyback) it on the cigarette fuse in the trunk/boot
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