Mercedes Sat Nav in a W123 - Page 2

V12 · 20-11-2009, 12:43 PM

On my old 190 i tested it with a multimeter. It spiked very quickly at around 2v from memory and the faster i drove the faster the frequency between the spikes but the voltage stayed at 2volt'ish...was about 5 years ago though.

Stratman · 20-11-2009, 01:07 PM

The reason the voltage stays the same is that the 'mark/space' ratio of the signal stays the same. This is the ratio between the width of the pulse (mark) and the gap between the pulses (space). As the speed increases so does the frequency of the pulses, but the ratio doesn't change. 2V implies a mark/space of about 1:6

What you need is a frequency meter. Some multimeters have a frequency function which would do the job.

V12 · 20-11-2009, 01:43 PM

I'm glad someone knew what i was trying to say and interpreted it into proper technical speak!!

jaymanek · 20-11-2009, 08:01 PM

guys it worked!!

Hooked up a wire from pin 1 of the iso plug to the green and black wire of the plug on the back of the speedo and hey presto my sat nav knew where i was once i started moving!

SOLVED!

Thanks to everyone who input above otherwise id be "magnetising my tire"

Stratman · 20-11-2009, 08:25 PM

Great job.

Now you need to tell it the tyre size and how many pulses per revolution it is getting. On COMAND the tyre size can be done from the unit itself but the number of pulses needs STAR. I don't know about APS though, other than it will almost certainly need to be done.

jaymanek · 21-11-2009, 11:29 AM

Yep ill enter the tyre size in as i dont think its quite right.. its telling me to prepare to turn ages before the turn!

jaymanek · 23-11-2009, 01:51 PM

guys on the back of the unit there is another plug that looks like it takes a standard gps aerial... anyone know what this is for?

obviously I have used the mercedes gps plug..

20-11-2009, 12:43 PM	#16
V12 Hardcore MB Enthusiast Join Date: Jun 2002 Location: South Car: CLK270CDI - Daily Posts: 1,593	On my old 190 i tested it with a multimeter. It spiked very quickly at around 2v from memory and the faster i drove the faster the frequency between the spikes but the voltage stayed at 2volt'ish...was about 5 years ago though. __________________ '51 E320cdi on 19's - CBR600F4i - CLK270cdi : Wheels needed!

20-11-2009, 01:43 PM	#18
V12 Hardcore MB Enthusiast Join Date: Jun 2002 Location: South Car: CLK270CDI - Daily Posts: 1,593	I'm glad someone knew what i was trying to say and interpreted it into proper technical speak!! __________________ '51 E320cdi on 19's - CBR600F4i - CLK270cdi : Wheels needed!

20-11-2009, 08:01 PM	#19
jaymanek Hardcore MB Enthusiast Join Date: Nov 2002 Location: Nuneaton Warwickshire Car: 560 SEC AMG Widebody, 560 SEC AMG, W124 500E, W123 280CE, W123 200, R107-500SL Posts: 9,190	guys it worked!! Hooked up a wire from pin 1 of the iso plug to the green and black wire of the plug on the back of the speedo and hey presto my sat nav knew where i was once i started moving! SOLVED! Thanks to everyone who input above otherwise id be "magnetising my tire" __________________ Mercland is listed here on MBClub please click to see services and discounts available. 1980 123-200 in Sahara Yellow 1985 123-280CE in Champagne 1988 500SL in Met Light Blue Now with Leather 1988 560SEC AMG in Midnight Blue 1989 560SEC AMG Widebody 1993 E500 Brabus in Silver with lots of toys! 1 of 29 UK Supplied Cars Gallery Link

20-11-2009, 08:25 PM	#20
Stratman Hardcore MB Enthusiast Join Date: Jun 2003 Location: Sunbury Car: W202 C180 Estate RIP W203 C200 CDI Estate Posts: 994	Great job. Now you need to tell it the tyre size and how many pulses per revolution it is getting. On COMAND the tyre size can be done from the unit itself but the number of pulses needs STAR. I don't know about APS though, other than it will almost certainly need to be done. Last edited by Stratman; 20-11-2009 at 08:30 PM. Reason: To add more info

21-11-2009, 11:29 AM	#21
jaymanek Hardcore MB Enthusiast Join Date: Nov 2002 Location: Nuneaton Warwickshire Car: 560 SEC AMG Widebody, 560 SEC AMG, W124 500E, W123 280CE, W123 200, R107-500SL Posts: 9,190	Yep ill enter the tyre size in as i dont think its quite right.. its telling me to prepare to turn ages before the turn! __________________ Mercland is listed here on MBClub please click to see services and discounts available. 1980 123-200 in Sahara Yellow 1985 123-280CE in Champagne 1988 500SL in Met Light Blue Now with Leather 1988 560SEC AMG in Midnight Blue 1989 560SEC AMG Widebody 1993 E500 Brabus in Silver with lots of toys! 1 of 29 UK Supplied Cars Gallery Link

20-11-2009, 01:07 PM	#17
Stratman Hardcore MB Enthusiast Join Date: Jun 2003 Location: Sunbury Car: W202 C180 Estate RIP W203 C200 CDI Estate Posts: 994	The reason the voltage stays the same is that the 'mark/space' ratio of the signal stays the same. This is the ratio between the width of the pulse (mark) and the gap between the pulses (space). As the speed increases so does the frequency of the pulses, but the ratio doesn't change. 2V implies a mark/space of about 1:6 What you need is a frequency meter. Some multimeters have a frequency function which would do the job.

23-11-2009, 01:51 PM	#22
jaymanek Hardcore MB Enthusiast Join Date: Nov 2002 Location: Nuneaton Warwickshire Car: 560 SEC AMG Widebody, 560 SEC AMG, W124 500E, W123 280CE, W123 200, R107-500SL Posts: 9,190	guys on the back of the unit there is another plug that looks like it takes a standard gps aerial... anyone know what this is for? obviously I have used the mercedes gps plug.. __________________ Mercland is listed here on MBClub please click to see services and discounts available. 1980 123-200 in Sahara Yellow 1985 123-280CE in Champagne 1988 500SL in Met Light Blue Now with Leather 1988 560SEC AMG in Midnight Blue 1989 560SEC AMG Widebody 1993 E500 Brabus in Silver with lots of toys! 1 of 29 UK Supplied Cars Gallery Link

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