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DIY - First Gear Start Switch Installation

52679 Views 118 Replies 31 Participants Last post by  northfraserauto
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.
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Great job on the DIY write up!
can i use this device to my SL600, 1993 ?
can i use this device to my SL600, 1993 ?
Yes you can, one of our other members with an SL600 has fitted one.
can i manually switch to 1? and then shift to 2nd and 3rd....
can i manually switch to 1? and then shift to 2nd and 3rd....
You can do this anyway without a FGSswitch.
First gear

I have a '91 SL300 and I understand that it starts off in 2nd gear. How do you make it start of in 1st gear all the time?
kick down the gas pedal, or manually shift, I saw a relay for about 20 bucks, or you can buy a module or something like that google it, they want a couple of hundred.

do it manually, best bet. just dont stick it reverse on your way back to D lol
I have a '91 SL300 and I understand that it starts off in 2nd gear. How do you make it start of in 1st gear all the time?
You have to do a valve body modification to the transmission. I don't remember the details, but it may be a simple as changine the postion of a ball and spring. I don't believe first-gear start can be accomplished with any electronic modules or electrical modifications.
First Gear Start Switch Installation of VSS-FGS

Hello Chaps

Installed the FGS Switch last night.

I appericate the the ABS sensor generates 96 pulses per one rotation of the wheel.

We used Redliners instructs and used the VSS. (Which are now on FGS website. :thumbsup:).

Q1: Should I be receiving 96 pulses via the VSS? I'm not and had to select other and set it to 11 to get the correct speed.

Q2: By changing this standard abs tooth setting to other and setting it to 11. The unit worked. I then drove it home via the motorway. After coming off the motorway I checked it the system was still working. It wasn't.

You turn off the ignition and then on again. All three lights come on and then only the power stays on.

Kickdown light is lite when you manual put the tranmission into "B".

Powered down unit.
Made changes by the software to change up and down speed.

1st Gear light still off.
Software also indicates 1st gear off.

Any ideas?

Also sending this message to FGS.
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Jeff, I didn't have to change the standard settings only the tyre size input and change up and down speeds.

It almost sounds as if a wire has come adrift. What sort of connectors did you use?

I always think that if something was working properly then doesn't it's usually something silly like a bad connection.
It only worked if we changed the pulse to 11.

I will rechecking all the wiring again. We solder everything. :(
Do you know what unit sends the VSS the pulse?
Hi Redliner

In your instructions the Vss cable is a Green wire with a Black stripe.

I believe mine is a Black wire with a Green stripe.

91 500Sl

Hmmmm wonder if the colour has changed or I'm connecting to the wrong wire.....
Jeff I've looked up the AllData CD for a '91 500SL and it shows the Vss wire as Green with black stripe.

It should come in on pin 1 of the A plug of the radio connector (see diagram)


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Thanks for looking.

Another thing I noticed.

Is when you put the key into position 2 the FGS switch goes from off to on. But when you start the engine it switches back.

We are going to recheck the wiring on Tuesday.

I've just checked with my car.
Position 2 all three module lights on whether switched to E or S.
With the car started in P only the Power light stays on with the switch in the E position, when switched to S all three lights are on.

You could check that the Red wire from the module has been connected to the correct Black/Red wire as there are two.

It should be connected to the Black/Red wire that is paired with the Black wire from the B position switch not the Black/Red wire paired with the Black/Red/Purple spots from the SE selector.
Hi Redliner.

At SK house. Seems either I can't read or I'm just being thick.

When in E it does as you discribe.
When in S it does as you discibe.

So its working...... Ooooooooops

What it doesn't explain is why I have to change the VSS number down to 11.

The chap at FGS suggest the following.

1.The number for VSS = your SL diff ratio multiply by 4 (for example 560 SEC euro , diff ratio 2.65*4=11)

So I'm not sure how yours is working if you used the VSS.

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Without plugging my laptop in and checking I'm almost sure I didn't fiddle with ABS tooth setting only the tyre size and it seems to work OK :confused:

I modified the FGSswitch wiring diagram but I can't add it to my installation guide because there is a per post photo limit of ten.

If it's of any use to anyone (click to enlarge)


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