Ben,

Take the reading with the O2 sensor plugged in and the engine warmed
up.  Touch the +'ve of the VOM to the connector where the green O2
wire meets the white O2 wire (or is it black - can't remember).
Attached the -'ve of the VOM to an engine ground.  You should see a
fluctating voltage between .4 and .7 volts.  It never stays steady -
always fluctuating above and below .5 volts.

If there are more readings below .5 then you are a bit lean.  If most
readings are above .5 then you are running rich.

If your reading is way higher than .5 (say 1.5) then you are running
VERY rich and have either:

(1) a sensor that is bad which is enrichening the entire system and
the ECU can't adjust for, or

(2) you have a bad O2 ground wire (the outer sheath of the green coax
O2 wire from terminal 19 on the ECU).

Laurence Smith
Hamilton, ON
90 Westy (fanumbos)

> -----Original Message-----
> From: Vanagon Mailing List
> [mailto:vanagon@gerry.vanagon.com]On Behalf
> Of Ben huot
> Sent: Tuesday, May 07, 2002 2:20 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: A damn OS question again, yea!!! now i need some
> help, it's my
> turn....
>
>
> Hi guys, i receive my new Oxygen Sensor today
>
> but i don't see any difference with the old one!!!!
>
> One question:
>
> Many people are saying that an OS produce voltage when hot
> and unplug!!!!
> Between 0.1 to 1 volt. (rich mixture or poor
> mixture)!!!!!!!!!!!!!!!!!
> For now I don't agree!!!
>
> Should I unplug the battery to reset the ECU?
>
> 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?
>
> Best regards, Ben
> http://www3.sympatico.ca/huotx/engine1.htm
>
> Ps: I have 2 new OS sender (error from the company) and the
> old one, they
> all give me the same reading!!! Is my $100 voltmeter faulty!!!!
>