MFA and cruise together - speed sensor wiring

[abatzis2 at hotmail.com (abatzis)]

ok, jumping in...
you said the mfa speed sensor has 3 wires to the regular one's 2? did
you figure out which wires corrospond to the 2 on the regular sensor? if
so, why not just run the cc wiring in parallel with the mfa wiring and
isolate the cc circuit with diodes or something?

----------------------------------------------
Michael Abatzis
New Orleans!
'87 Scirocco 16v, sick right now... 
'88 Scircocc 16v, RIP
--------------------------------------------

> -----Original Message-----
> From: scirocco-l-bounces@scirocco.org 
> [mailto:scirocco-l-bounces@scirocco.org] On Behalf Of T. Reed
> Sent: Monday, August 11, 2003 4:01 PM
> To: scirocco-l@scirocco.org
> Subject: MFA and cruise together - speed sensor wiring
> 
> 
> I can't seem to find anything too helpful about how to wire 
> up both the mfa and the cruise control to the speed sensor. 
> If you folks know
> -anything- about how to do this I'd really appreciate hearing 
> about it.
> 
> The best I came up with was the pin on my instrument cluster 
> that is labeled "Hall-Geber" (I assume that means Hall 
> Sender) on the flexible circuit board and if you trace the 
> wire it -does- end up at one of the three pins on the speed 
> sensor. I can't imagine why the speed sensor signal would go 
> beyond the instrument cluster other than for cruise control, 
> or maybe a radio with speed-based automatic volume control. 
> Or motronic... but this cluster is from an 86 golf 8v. VW 
> didn't use motronic until well after 86, right?
> 
> I checked the wiring harness in the car and there is no wire 
> it in corresponding to the "hall geber" pin.
> 
> I hooked it up an oscilloscope to that wire and the cluster 
> ground and all I could get was a couple millivolts (like.. 5 
> mV or so) of increase from the baseline noise (which I was 
> never really able to get rid of) when I spun the speedo drive 
> quickly by hand. The way I see it, that could very well just 
> be coupling/crosstalk between wires on the cluster.
> 
> With that kind of minimal result, I'm hesitant to "just hook 
> it up" and risk frying my instrument cluster and/or cruise 
> control computer. It seems to me like the output should be on 
> the order of volts or at least tenths of a volt.
> 
> The other thing is.. the "troubleshooting cruise control" 
> section of the bentley specs the resistance across the 2 
> speed sensor wires as 90-110 ohms. But between any of the 3 
> wires on the speed sensor I have it is an open circuit.
> 
> I've searched Google Groups and vwvortex and read hundreds of 
> messages.. I can't think of anywhere else to look.
> 
> -Any- help would be appreciated!
> 
> Thanks
> -Toby
> 
> 
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> 
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