107 300SL Speedometer - electronic?

[David Pemberton]

Hello

Is the speedometer on a 1987 300SL mechanical or electronic? I've been peering at the thing through the speaker aperture and I'm baffled.

There's no sign of a drive cable. There is a wire with a single pin plug to the back of the speedometer, however when I unplug it the speedometer still works - any idea what this wire is feeding?

The car has ABS and the 300SL has the engine/autobox per the W124 300E. The car does not have cruise control or an outside temperature guage.

The speedometer part number (from the face of the dial) is 1075420857.

This is all in aid of trying to find a speed signal for my Audio 30 APS navigator.

Thanks for any help.

 

[television]

http://www.detali.ru/cat/oem_mb2.as...&L=765.707&CT=F&cat=574&SID=54&SGR=585&SGN=12

It is electronic, is there a wire on pin 1 of the multi plug on the radio

 

[David Pemberton]

Hello Malcolm

There is a wire on Pin 1, but the connector isn't an ISO connector it's an older Mercedes connector like the one on the upper right of this picture:

http://www.nexxia.co.uk/car_stereo_fitting_kits/images/PC2-11-4.jpg

According to the fitting instructions for the Becker Grand Prix radio that came with the car, Pin 1 (the pin that's out of line with the others) is an earth/chassis/- connection. The other three are permanent live, ignition live, & instrument lights.

I don't think that the wire on the back of the speedo goes to the radio plug. Would it feed anything else (ABS?) or perhaps it is pre-wired for an unused feature (cruise?). When I worked as a product planner for Nissan our cars had lots of unused wires in the harness, there were just too many options to make a haness for every combiantion.

Interesting that a car which is 22 years old has an electronic speedo, still the 300 SL was a fairly heavily updated car (ABS, seat-belt tensioners, electronic control of transmission).

Thanks for the link to the parts diagram. The part number doesn't match, but what does correlate is that for the 300 SL there are no mechanical drive cables listed.

Thanks for any further ideas.

 

[television]

Info on the 107 is almost non existent, but I can get certain 124 info. When I turn on in the morning I will see what I can find. The 2 cars have lots in common

 

[brianbrian]

Sorry to butt in, 124 are manual drive to gearbox, early sl 129 might be the same, hope this helps.

 

[television]

Sorry to butt in, 124 are manual drive to gearbox, early sl 129 might be the same, hope this helps.

Please do butt in,,all help needed, I think that 86-87 was the change on all of them, I have been short on time for a few days

 

[David Pemberton]

Hello

I'm back to answer my own post for the sake of anyone who searching the forum for this in the future.

107 041 type 300 SL has an electronic speedometer with a speed signal OUTPUT from a single pin terminal at the centre rear of the speedometer.

Some more info for if you are looking to use the speed signal e.g. for a Satnav.

Helpful manuals:

S-2369-107 Mercedes Benz of North America Electrical Trouble Shooting Manual, Model 107, Model Years 1983-1989 (yes worth it even for European market cars like mine).

Haynes Automotive Repair Manual for Mercedes 350 & 450 types 350SL, 450SE, 450 SEL, 450 SL, 450 SLC (useful for how things come apart, go back together).

To access the speed signal you need to remove the instrument cluster. First remove the steering wheel per the Haynes manual (prying out the MB star emblem to access a 10mm Allen bolt) - takes a couple of minutes, the bolt might be very tight. Remove the instument cluster per the Haynes manual - takes 30 seconds as amazingly for a Mercedes it is just a push fit.

The speed signal connector is, in constrast to the push-fit instuments, wonderfully over-engineered and comprises a screw-down retaining ring and a peg to locate the connector socket. To intercept the speed signal carefull cut back some of the insulation, solder on a wire, and use heat-shrink to make the job good again.

According the the US electrical manual the speed signal is also used for: engine management system, ABS (in addition to wheel & differential sensors), and the cruise control (if you have one).

Now I've just got to find a neat place for the GPS aerial. In my 202 it got a good signal sitting just under the dashboard on top of the centre air vents (so totally invisible, but of course it could "see" the sky because the plastic dash doesn't screen the radio signal). In the SL I get no signal at all putting the aerial under the dashboard - wonder if it as plastic/metal laminate?

 

[D1gger5]

GPS requires line of sight to the satellites.

Metal and certain building materials attenuate the signals.

Best location would be on top of dash or windscreen area to minimise attenuation. Helicopters and planes have the antennae on top outside their fuselage (screwed/bolted to the skin/ribs and then cabled to the Navigation sub-system.

Diggers

 

[television]

Pleased that you found it Dave, and nice to know that it is there.

How about 6 down made into a license holder
http://www.badland.co.uk/list_products.php?cat=gps&gclid=CLWPupjVpJoCFUM-3godtFjU-A

 

[David Pemberton]

Pleased that you found it Dave, and nice to know that it is there.

How about 6 down made into a license holder
http://www.badland.co.uk/list_products.php?cat=gps&gclid=CLWPupjVpJoCFUM-3godtFjU-A

Thank you Malcolm, a very nice bit of lateral thinking!

I'm keen not to have a visible antenna for many reasons: aesthetic, orginality, image.

"GPS requires line of sight to the satellites." - well it requires an electromagnetic line of sight for the spectrum used by gps radio tranmissions, not a visible line of sight. In my 202 and my Polo the antenna works fine mounted immediately below the top of the dashboard: nice and discrete.