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Info guides and mods

SAM Unit (Fuse Box)

It's a name that gets banded around especially by Roadster owners but not that many people actually know what it is, even less know what's inside.

Modification Details

Many thanks to Dave Guile from Chequered Flag in Strood for donating this part.

So What Is The SAM Unit?

Essentially it is a fuse box with internal relays and a microprocessor that controls
almost all of the electrical functions of the car. The processor is flashable so it can
be taught new tricks by way of a TAN code, these tricks include paddle gear shift,
auto door locking, automatic gear change, day time running lights, cruise control etc.

What Does SAM Stand For?

Signal Acquisition & Actuation Module.

Where Is It?

It can be found at the top of the footwell, passenger side of a RHD smart city coupe/cabrio, drivers side of a LHD smart city coupe/cabrio and the drivers side of a Roadster.

What Does It Look Like?

Just a plain boring black box with fuses pushed into the front.
Although the SAM units all look the same, the new 452 internals are slightly different.

What About The Bits We Can't See?

The top side is where most of the wiring goes to, there are 10 connections and a positive input.
All inputs are labled. Each circuit has its own earth point around the car.

There Is Something Missing

Damn right, Relays. Most cars have relays in the fuse box, these control the horn, wipers,
indicators, lights etc. The relays visible on the smart are for the fog light and heated seats.

How Does That Work Then?

No different except in this case the relays are actually inside the SAM unit.

Inside The SAM Unit

Remove the three Torx10 screws.

Unclip all the plastic clips around the outside

With the top off you see the main fuse connections

With it removed from the box you see the relays and connectors

The board is in 4 parts and is bent around on itself,
you can see the back of the tracks become damaged.

PCB 1, 2 and 3 fold open and a flat plastic retainer can be removed

PCB 4 is populated with the microprocessor and many small relays

This shows the main functions of the relays on PCB 2

This shows the single relay on the back of PCB 4

No User Servicable Parts Inside

You can say that again, if you get water in this there is nothing that can be done.
There is nothing you can take out or change, everything is soldered directly to the PCBs.

What About Microchips?

There are surprisingly few IC packages inside the SAM unit. The main one however is the Motorola MC9S12DG256C which is a 112 pin 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit (HCS12 CPU), 256K bytes of Flash EEPROM  and a whole load of other stuff that means very little to me. If you want to know more about this chip. Click here.

SAM connections

700cc Fortwo And Roadster
N11-1 Wire Colors Connection Fuse
1 Black Yellow/White Black Window switches 4
2 Black Red Heater blower motor 3
3 Black Yellow AirCon connections 8
4 Pink Red Wiper stalk and relay 2
5 Violet Front fog lights 13
6 Red Black ESP controller 14
7 Pink Radio 12
8   Master engine relay 10
N11-2 Wire Colors Connection Fuse
1 Brown Green ECU (MEG unit) 9
2 Black Wing mirror and rear window heater 28
3 Red White Trip PC, OBD, speedo voltage 11
4 Red Green Safety triangle 11
5 Brown Earth  
6 Yellow Soft top motor forward 29
7 Blue ECU (MEG unit)  
8 Red White Soft top motor reverse 29
N11-3 Wire Colors Connection Fuse
1   Rear window wiper 17
2 Grey Green ESP control unit 18
3 Red Yellow Soft top switch, mirror adjuster switch 19
4 Blue Trip PC, OBD, Speedo voltage 20
5 Blue Yellow Cigarette lighter socket 21
6 Grey Red Low beam 22
7 Blue Green Low beam 23
8 White High beam 24
9 White Blue High beam 25
10 Red Black Fuel pump 16
11 Blue Red Brake light switch 26
12 Red White ECU (MEG unit) 24
N11-4 Wire Colors Connection Fuse
1 Red Black Ignition position 1  
2 Red Blue Connector Z24  
N11-5 Wire Colors Connection Fuse
2   Rear window wiper 17
3 Red Wiper relay  
5 Brown Earth  
6 Red White Light stalk 5
7 Brown White Boot release/window switch 6
8 Red Green Interior lamp 12
9 Brown Yellow/Grey Rear lights 7
10 Green Connector Z36 30
11 Black Pink ECU (MEG unit) 16
12 Yellow Black Connector Z35 10
N11-6 Wire Colors Connection Fuse
1 Blue Starter 1
2 Pink Electric air pump 32
N11-7 Wire Colors Connection Fuse
1 Red White Steering assist control 35
2 Red ESP control unit 34
3 Red Black Ignition main 33
N11-8 Wire Colors Connection Fuse
2 Brown White Earth  
3 Grey Red Wiper stalk  
4 Yellow White Right door switch  
8 Yellow Green Crash restraint  
9 Pink Red Wiper motor  
10 Green Blue Light stalk and trip PC  
11 Black Green Cruise control stalk  
13 Brown Earth  
14 White Black Speedo CAN low  
15 Brown Red Speedo CAN high  
16 Red Steering wheel  
17 Yellow Wiper stalk  
18 Blue Black Door switch  
19 Yellow Red Left door switch  
20 Green Boot switch  
31 Blue Blower multi-way switch  
32 Blue White Soft top strut switch  
33 Pink Black Soft top strut switch  
34 Grey Handbrake switch  
35 White Soft top power switch  
38 Grey Blue Ignition position 2  
39 White Black ECU and steering assist CAN low  
40 Brown Red ECU and steering assist CAN high  
N11-9 Wire Colors Connection Fuse
1 Black White Left turn signal  
2 Grey Aircon switch position 2  
3 White Grey OBD diagnostics  
4 Grey Blue Interior lamp  
6 Pink Fog lamp relay  
7 Pink Red Cruise control stalk  
9 Blue Yellow Auto light switch  
10 Green Blue Cruise control stalk  
11 Black Green Right turn signal  
12 Violet Blue Hazard switch switch  
13 Blue Central locking switch  
14 Violet LIN Bus to Trip PC & auto light/wiper sensor  
16 Blue White Wiper relay  
18 Blue Yellow Auto light switch  
20 White Key remote receiver  
31 Green Aircon switch position 1  
32 Black Red Heated rear window switch  
33 Yellow Red Light stalk  
34 Yellow Light stalk  
35 Yellow Green Light stalk  
36 Green Blue Wiper stalk  
37 Yellow Black Fog lamp switch  
38 Blue Light stalk  
39 Black Green Light stalk  
40 Red Green Wiper stalk  
N11-10 Wire Colors Connection Fuse
1 Brown Foot well earth  
2 White Aircon compressor  
3 Brown Green Coolant radiator fan  
4 White Blue Door open signal 31
5 Grey Blue Door closed signal 31
6 Blue Red Horn 31
7 Yellow Intercooler fan 15
8 Red Boot open solenoid 31
N11-11 Wire Colors Connection Fuse
1 Red 12 volt from battery  

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