Introduction: Ignition Free Electric Windows on Smart Car (Smart 451)

About: I rather like "to make" than "to consume". I've been programming for iOs for a while just to see if I can. I love making cases and pouches for my gadgets, but currently it seems I'm running out of projects. Bu…

Following this instructable may void your Smart’s warranty. Also, it may be that having ignition free electric windows may violate standards or vehicle regulations (I could imagine that this came into place to prevent kids from playing with the windows and getting hurt by them when left alone in the car).
Don’t do anything that could reduce your car’s safety. If you follow this instructable, you should be familiar with car electrics and you do it on your own risk. I may not be held liable for any damage resulting from this mod.

My introduction got a little long this time, so if you just want the essentials,
skip from here.....

I didn’t intent to do much this weekend.
Acutally, I wanted to add a new blog post, start my next app-project or continue writing my instructable about my iPhone app “Gas By Numbers”, Unfortunately, nothing of all this happened.

Being lazy, I just surfed the internet.
My Smart car came to mind, and how I’m still fed up with the automatic shifting of gears (it’s not a real automatic transmission), even after 3 years. My Smart has the so called “soft touch” which means that I can select to have the transmission shift automatically or manually. I’d prefer the auto-mode, but I still hate that the gear shifting points are set in a way which render it more or less useless for every day use. Due to a lot of truck traffic on my daily commute, I rarely reach the speed needed for auto to shift into 5th gear. So I have to manually shift to 5th when in auto, but then the auto mode doesn’t come back. Instead, shifting is switched to manual.
Also, when in manual mode, my Smart tells me via the display when it would be energy efficient to shift into the next gear, but in auto, the gear shifting takes place at much higher speeds than what it tells me when in manual.
So I was looking for a hack on the gear box software. After all, 3 years have passed since I first got annoyed by this fact and it’s just a matter of software settings.
Well, there aren’t any hacks except for increasing your Smarts horse power via chiptuning. But this probably worsens fuel efficiency, so this is not where I want to go. And I don’t need more speed, I’d just look for a more convenient “shifting experience”.

…… to here.

Anyway, while searching for a gear box software hack, I stumbled over a forum where people commented on something like a “fuse extender” for the electric windows which made me curious. This little gadget sells for about 20-30 bucks and provides a means to operate your electric windows without having to turn on the ignition.
After looking at it, I remembered that I often times leave the motor running until my windows are closed before switching my Smart off. Because if you first turn off the engine (turn off ignition), the electric windows won’t operate.
So if you turn off the engine first, you have to turn on the ignition again to close the windows.
Something I was annoyed off, too, but never spend much time thinking about.

Hmmm. Getting a little electric something to make the windows operate without ignition seemed great. But on Saturdays, stores close somewhere between 1 and 6 pm and it was already about 3 pm.
Also, spending that much money on such a little thingy seemed overpriced, too.

(Spoiler alert: the DIY version will be free if you have some electrical stuff at home already, otherwise it shouldn’t be more than a couple of cents, although you’ll mostly have to buy complete sets of terminals, heat shrinking tube and such, so that your initial cost to get what’s needed may be around 10 bucks. But the remaining parts can be used for other projects later).

So I checked for explanations on the gadget to see if I can DIY something. I stumbled over Kane’s website (which I already found 3 years ago and which is a great source of information on everything “Smart”). He already has an instruction on what to do, but the hack seemed too easy and clever as not to share it here. You can find Kane’s original instructions here

Basically, the electric windows don’t operate without ignition because the fuse is not connected to permanent live, meaning that if ignition is turned off, all power is taken from the fuse.

This instructable shows how to get fully operational electric windows of a Smart 451, no matter which position your key is in.
Other (older) models can also be modified, but you’ll have to check which fuse you have to work with. I don't know if newer models work, too.

Step 1: Tools and Supplies

  • Spade connector
  • Spade terminal
    (Ensure you use the proper size spade connectors)
  • Heat shrink tube
  • Wire (at least 1.0 mm2 cross section, AWG18, approximately 7 inch long as recommended by Kane)
  • Cable stripper
  • Wire cutter
  • Crimping pliers
  • Smart car manual

Step 2: Locate Your Fuse Box

The fuse box is located right under the steering wheel column.
For the Smart 451, locate fuse #3.
To ensure you’re working on the appropriate fuse, please consult your Smart’s user manual. You can find the information in the rear portion of the manual.

Older and newer Smart models may use a different fuse number for the electric windows.

The fuse in my Smart is rated at 20A. It may be that other models are rated differently or that there are country specific ratings. So don’t take my rating for yours. Ensure that you replace the proper type of fuse (basically, just reuse the fuse that is used now).

Step 3: Pull the Fuse and Prepare the Cable

Before pulling the fuse and starting to work on the car’s electric components, be sure to turn the ignition fully off. It’s maybe best to just remove the key.

I didn’t have an 18AWG cable available, so I just used a speaker box twin cable.
  • Pull the fuse for the electric windows (fuse #3, verify fuse # in your car's manual)
  • Strip off the cable insulation for the spade connector
    (Drill the ends of the twin cable together if you use the wrong cables like I did)
  • Apply the spade connector
    (check that it's properly connected by lightly pulling at the cable)
  • For the following step, don’t connect the spade connector yet. It’s hard to remove once inserted:
    To get the proper length of the cable, hold the spade connector close to the lower pin in the fuse box for the electric windows and route the cable to one of the spare fuse spots to the left of the fuse box. Consider the extra length that is needed to connect the cable to the “foot” of the fuse.
    Cut off any excess cable.
  • Strip off the cable insulation for the spade terminal
  • Apply the spade terminal to the cable
    (check that it's properly connected by lightly pulling at the cable)
  • Apply heat shrinking tube to both connectors to ensure electrical safety. You don’t want the bare metal to touch other metal parts or connectors once the cable is installed
    (This wouldn’t have been necessary for my spade connector due to it coming with insulation, but I wanted to make sure. The spade terminal will be located outside the fuse box once it’s installed, so ensure that the whole connector is isolated by the heat shrinking tube).

Step 4: Install Your DIY Ignition Free Electric Windows Solution

  • Insert the spade connector into the lower pin for fuse #3
  • Insert one “foot” of the electric windows fuse into the spade terminal of the cable
  • Insert the other “foot” in one of the spare fuse holders on the left of the fuse box. (I used the lowest fuse holder so that the cable can be as short as possible).
I tried different spare fuse spots, and all of which I tested worked. But it could be that not all of them provide permanent live.

Once the fuse is connected, try out your electric windows with the ignition turned off.
If your windows don’t work, check if you followed all steps properly.
If everything works as expected, tape the cable to the fuse box to ensure it’s not getting pulled out accidentally.

You can now shut your windows, even if you turned of your Smart’s engine without turning the key to the 1 position again.
This solution is inexpensive, saves on gas and is convenient.