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Vanagon Nut
Samba Member
Joined: February 08, 2008
Posts: 10524
Location: Sunshine Coast B.C.
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 Posted: Thu Jul 26, 2012 1:01 pm Post subject: Throttle Switch: Quality of Open, Close Signal? |
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Hi all.
Had read this thread a couple on throttle switch pivot repair.
http://www.thesamba.com/vw/forum/viewtopic.php?t=455400&highlight=
It made me wonder if my throttle switch has corroded contacts.
I'm certain that my throttle switch closes just off idle, but....
If the throttle switch contacts were dirty or corroded, if one used a graphing meter to measure the quality of the signal ECU sees from the throttle switch when it closes, would they see a slope up to "on" instead of clean square wave?
e.g. would a dirty switch that shows continuity on a VOM, still cause and issue with the deceleration portion of ECU? (thus cause surging on deceleration)
I only have one throttle switch so don't want to crack it open unless I have good reason to.
Thanks,
Neil.
_________________
1981 Westy DIY 15º ABA
(VW Gas I4)
1988 Westy DIY 50º ABA
VE7TBN |
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 43002
Location: at the beach in Northern Wokistan
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| Posted: Thu Jul 26, 2012 1:59 pm Post subject: |
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| Neil - it would be lots of little steps if it was bad. I am not a vanagon person but didn't the vanagon have a surging issue that was fixed with a special connector wire between the AFM and harness? |
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Vanagon Nut
Samba Member
Joined: February 08, 2008
Posts: 10524
Location: Sunshine Coast B.C.
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| Posted: Thu Jul 26, 2012 4:16 pm Post subject: |
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SGKent: Thanks for that.
My mechanic kindly hooked up his Vantage and showed me the signal: good square wave open, close of throttle switch. So it for sure works. He even gave a demo of this tool showing various other tests.
The issue I think you refer to is called "Vanagon Syndrome". My mechanic had loaned me one of those AFM connectors to try and see if issue dissapeared. It didn't seem to though I should have tested with it longer.
With VS, my understanding is that wear on the resistive strip, etc. causes the AFM to send dirty signals to the ECU. During that time one usually experiences bucking issues. After seeing enough of these dirty signals, the ECU goes into a default mode of shutting off the engine.
I moved the circuit board in the AFM so wiper is on a new portion of the resistive strip and installed a 22 uf tantilum capacitor (does similar or same thing as special connector). These made no difference.
Meh. 
Neil.
_________________
1981 Westy DIY 15º ABA
(VW Gas I4)
1988 Westy DIY 50º ABA
VE7TBN |
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