At 02:19 AM 5/7/2002, Ben huot wrote:
>Explanation: I get the van too normal operating temperature (OS is plug); I
>unplug the OS and test voltage to this one (ground the negative and I touch
>the OS sender wire with the positive of the voltmeter); I get about 450MV
>(it means no reading), I never get .1 to 1 volt. If i touch the van side of
>the OS wire only I get a steady .5 Volt when the OS is unplug. When i plug
>back the OS (Van running and hot) it get down to 450MV or so but sometime
>it give me a brief .7 volt and it goes back very fast to .350MV or no
>reading!!!!!. (back and forward) I never get a steady reading; yes my
>voltmeter wires are well attached.
>
>
>What are your suggestions?

What you describe sounds normal to me, but to be certain you have to start
with engine cold I think.

Start with cold engine, OS plugged in. *Unplug the OS heater.* Measure from
OS to ground and start engine.  Reading should be near .5 volt
steady.  Warm up engine and plug heater in -- voltage should start to
oscillate above and below .5 volt.  With an oscilloscope and x10 probe you
would see a sort of square wave, but with regular digital voltmeter you
will see only random readings that change above and below half a volt
(because the meter averages readings over half a second or so).  This is
normal behavior by the ECU forcing the mixture rich and then lean -- every
few milliseconds with engine running fast.

Unplug OS.  The van side will be steady near half volt, the OS side will be
somewhere between 0-1v depending on lean or rich mix.  It will change as
mixture changes -- throttle up and down, should see some response unless
mix is always rich or always lean.  It needs only a tiny bit rich or tiny
bit lean to change the output all the way.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"