I have retro fitted a St Nav in my P38 all is working except the pick up from the speed sensor, The sensor is working as the speedo etc. work and the abs light goes out at 5mph however nothing on the sat nav. I was told that the speed sensor feed is "dirty" and sometimes not enough for the sat nav to understand. Is there a way of cleaning the signal or boosting it ? if I connect to the speedo wire it stops the speedo working
Speed sensor Boost for Sat Nav
- Thread starter palace
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Datatek
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Can't understand why a SatNav would need a feed from the speedo, most SatNavs are quite cabable of calculating speed.
odysseus
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My year 2000 era Merc's sat nav had an input from the front wheel to record speed and distance. This was to help the (admittedly old school) sat nav cope if satellite reception was iffy. Could be similar on the P38?
I think it's so they work in tunnels - like assuming you don't suddenly about face it can still predict your location based on the speed data and the fact there's only one way to go.
Maybe also so that the satnav speed doesn't contradict the speedo speed, like in corners or with iffy reception.
Datatek
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TomTom et al manage quite well without a speed input.
stjohnsmythe
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drewster
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its a white wire will get back with the diag soon
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Ok on a straight road with no hills but on a twisting road up hill and down dale Sat nav speed calcs are as useful as tits on a Mars bar.
Datatek
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Funny that, GPS based speed indicators work quite well.Ok on a straight road with no hills but on a twisting road up hill and down dale Sat nav speed calcs are as useful as tits on a Mars bar.
Cheap replacement for a dodgy speedo.My TVR and rr had the same, my sat nav I could tell it to not use a speedo pulse so was not too much of a problem. It was odd, creeping in traffic and the sat nav did not move, in london could be minutes before it recalulated. I did however use a device that after magnetising the tyre, only half of it, the device would then detect rotation. Fitted many to many cars.
martyuk
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The speed signal comes from the BECM - which takes it's input from the ABS ECU.
The signal for the navigation system comes from the Yellow wire, on C255 (up to 1997)/C1279 (post 1997), Pin 10. It's a white, 20 way connector on the same side as the BECM fusebox (forwardmost connector).
The signal from there splices (on a vehicle with navigation) also to the HEVAC ECU. it ends up on pin 10 of C1350 at the navigation computer. (The red coloured connector at the Nav computer)
This info is from the 1999 ETM - and shows the connectors for the later Navigation System (MKIII NAV) with the 4 buttons and the rotary encoder on the left side of the screen. I'm not sure where the input goes into on the earlier nav system as I don't know if it had the same style connectors - RAVE only shows the one version sorry.
Hope this helps,
Marty
The signal for the navigation system comes from the Yellow wire, on C255 (up to 1997)/C1279 (post 1997), Pin 10. It's a white, 20 way connector on the same side as the BECM fusebox (forwardmost connector).
The signal from there splices (on a vehicle with navigation) also to the HEVAC ECU. it ends up on pin 10 of C1350 at the navigation computer. (The red coloured connector at the Nav computer)
This info is from the 1999 ETM - and shows the connectors for the later Navigation System (MKIII NAV) with the 4 buttons and the rotary encoder on the left side of the screen. I'm not sure where the input goes into on the earlier nav system as I don't know if it had the same style connectors - RAVE only shows the one version sorry.
Hope this helps,
Marty
Drop me a line, I have a couple kicking around.
martyuk
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Hmm...that's a bugger...
I wonder if the Nav unit you have requires a different type of input for the speed. From memory the vehicle uses a 12v square wave, and varies the number of pulses depending on speed.
What type of sat Nav have you fitted?
Marty
I wonder if the Nav unit you have requires a different type of input for the speed. From memory the vehicle uses a 12v square wave, and varies the number of pulses depending on speed.
What type of sat Nav have you fitted?
Marty
