DIY - First Gear Start Switch Installation

This is intended as a guide for anyone fitting a First Gear Start switch from FGSswitch to a four speed R129 V8 or V12 automatic gearbox.
Mercedes Benz SL V8 models with the four speed automatic transmission were designed to start in second gear. Fitting this First Gear Start Module will transform your car from the stately cruiser into a raw full on sports car.

Hopefully this guide will make fitting this electronic module a realistic project for any SL V8 or V12 owner.

No advanced electro or mechanical knowledge is required for this modification just confidence and patience.

When your FGS switch arrives just unpack it and you will see that basically it is just a black box with six wires that have to be connected to certain colour coded wires located within the centre console of your car.

It is just about possible to fit the switch without removing the centre console however I would recommend that for the little extra work involved it is far easier to fit the switch with the centre console removed.

Removing the centre console:

This video shows the removal of the centre console.

I will try to find a new link to this video

One important point, this video is for later USA models. When removing the climate control unit on earlier cars there are two plastic tabs on the centre console frame that have to be pulled downwards to release the climate control unit. See photos To access these tabs any after market radio mounts will have to be removed (very simple)






Tip. When removing the gear lever surround, to prevent marking the wooden console, insert a piece of thin card or paper between the surround and the wood and use a thin putty knife or similar to pry the surround from it’s plastic retaining clips which are located at the front and back of the surround. see photo



With the centre console removed you will now see the gearshift mechanism with two black sheathed cables coming from behind this mechanism. These are the cables which have to be connected to the FGS switch. I have removed a little of the sheath to expose the wires for jointing. See photos There is plenty of room and easy access to join the wires in this place which is why I recommend the centre console to be removed.




Positioning the Fgs switch:

I found the most convenient and accessible place to mount the Fgs switch is in the passenger foot well close to the centre console, see photo, this allows easy access for a laptop computer to be connected and programme the Fgs switch. This option should work well for both LHD and RHD vehicles.



Connecting the cables:

With the centre console removed pass a piece of garden wire or similar with a loop formed at the end through to the passenger foot well just below where the passenger airbag is situated.
Put the loose ends of the Fgs switch cables including the black co-ax cable through the loop in the draw wire and place a piece of tape to keep them from detaching and gently pull them through to the centre console position. The plug that attaches to the Fgs switch will be laying in the foot well with more than enough cable to work and position the switch with. see photo



Start with connecting the Earth/Ground cable/s. With the European models with the ES switch, connect both the Black and Orange wires to the earth point behind the flip up storage compartment on the centre console see photo.



Next connect the wires from the from behind the gear selector lever as shown in the photos.
Carefully slit the black sleeving on both cables to expose the wires. Tip: Slightly stagger these cuts so the connections are not all bunched together.
With the sleeve that contains the Black and Black/Red wires, connect the Blue wire to the Black wire and the Red wire to the Black/Red wire.
Then the other sleeve that contains a Black/Red/Violet dots and Black/Red wires connect the Brown wire to the Black/Red/Violet dots wire.





I have used a compression type of connector to join the wires which makes a safe and perfect electrical connection without soldering or ugly unsafe taped joints.

The final cable to connect is the Vehicle Seed Sensor cable. This can be taken from the ABS front wheel sensor co-axial cable which is located next to the brake servo in the engine compartment or more easily from the Vss (Vehicle speed sensor) cable which comes into the centre console with the other radio cables.
The Vss cable is a Green wire with a Black stripe.



Use the black co-axial cable that comes with the FGSswitch and using only the centre wire of the co-axial cable connect to the centre pin of one of the co-axial plugs that were supplied with the FGSswitch. The other end of the co-ax cable connect the centre wire only to the Green/Black Vss cable.

Cable ties are very cheap so remember to use plenty to make a nice tidy and safe job. Also be sure to place connectors and cables where they will not vibrate or rattle and lastly if you use a soldering iron in the car be very careful that you do not burn seats or carpets.