Which fuse from driver's side fuse box to use?

[flycaster]

Going to install a V-1 tapping into a fuse from the driver side fuse box (2017 C-300 coupe), but which fuse? I'd like to use a low amp fuse (5 to 7.5 amp) that is only on when the the ignition is on or the equivalent of having pressed the start/stop button two times without stepping on the brake. If you don't have a fuse box map (it should be in your trunk,) here's the pdf file

 

[flycaster]

80 views so far, and no one knows the answer??? How sad. I'm going to try fuse #206 which effects the glove box light.

 

[Giannis]

I'm going to try fuse #206 which effects the glove box light.

But that would mean that your V-1 would receive electrical current only when you open your glove box.

You need to see which fuse is connected with something that gets powered with ignition. Possibly the radio or clima?

 

[flycaster]

Thanks for the thought, but not quite so. If your car is not on and you open the glove box, no light appears. Turn car on, glove box light goes on. Thus indicating that the fuse is switchable. I will tap directly into the fuse as the fuse becomes activated with the starting of the car...and, or course, the fuse becomes inactive when the car is shut off. This last statement may not be wholly accurate as some car functions stay of for a short period after the ignition is off. I'll have to check that out.

 

[Giannis]

If your car is not on and you open the glove box, no light appears.

Yeap.

Thus indicating that the fuse is switchable.

A fuse is not switchable. A fuse is a fuse. A fuse is a safety item.

I will tap directly into the fuse as the fuse becomes activated with the starting of the car...and, or course, the fuse becomes inactive when the car is shut off.

The fuse doesn't get activated or shut off. It's a safety device.

This last statement may not be wholly accurate

Basically most of your car's function will not be able to be powered without the car being "on". In a more basic car, switching your key to position I will power everything but the engine. Put it in position II and engine receives power, you hear your fuel pump start, etc. Position III engages the starter motor obviously.

With the key not either out of ignition or in Position 0, the only things that get power is the light around the ignition and the interior lights, including your trunk's lights. Everything else gets powered with the key in Position I.

Things like your glovebox lights will only receive power when you open the glove compartment and the light circuit closes. Only then will current flow through the fuse. It's the switch that is activated by the opening of the glovebox, and not the fuse.

If I were you I'd try to find a subsystem that gets power with the equivalent of the key in Position I, since you have keyless go.

Things that operate with a switch/ actuator won't do, unless there's a secondary power line.

For example, in my S60, the radio unit also has the interior light sensor and has two power lines feeding it. One that is for the sensor and memory and a second for everything else. If I were to install a V-1 (whatever it is) I'd steal power from the first line.

If I were to install something that I want to have power always, I'd steal power from the power line feeding the ignition switch.

 

[flycaster]

Thanks for your good advice, Giannis. BTW, the V-1 is a Valentine-1 radar detector. However, it looks as though I won't be able to do the DIY as when it came to stuffing the power cord (essentially a thinnish phone wire) between the A-pillar trim and the windshield, the fitting was so tight that it was impossible to do. Folks have used this approach (Tap into fuse box at end of driver side dash, up the A-pillar and across the headlines to the driver visor) with their 2015 and 2016 C-300. But MB may have tightened up the fitting between the pillar and the windshield with the 2017 C-300 coupe, thus making this simple approach unworkable.

I know that if I took the A-pillar trim off, the install would work. But as this is a leased car, I do have some concern about ruining the trim. Perhaps you could help me with some directions on how to safely remove the trim?

 

[Giannis]

Perhaps you could help me with some directions on how to safely remove the trim?

From a quick google search:

http://www.pelicanparts.com/techart...76-BODY-Interior_Pillar_Panel_Replacement.htm

 

[flycaster]

Thanks again, Giannis. I've done a more thought Google and really haven't found anything that makes me comfortable with a DIY. So, I think I'll just ask my indy MB mechanic to do it for me. Should take him about 5 minutes...or less, won't cost much.