Three hundred ohms might as well be an open circuit compared to a 21 watt
stop lamp with a working resistance of around seven ohms.  A truly good
switch ought to have resistance in the low milliohms range.  However modern
multimeter ohmmeters apply very low energy to the circuit and occasionally
this might contribute to a discrepant reading.

I suspect that the issue with your original switch is a matter of you
pushing the plunger all the way with your thumb vs the transmission pushing
it only partway.

Yrs,
d

On Tue, Apr 11, 2017 at 10:10 PM, OlRivrRat <OlRivrRat@comcast.net> wrote:

>         Have been a Very Firm Believer in VOMs most of My life > Until
> Today ~
>
> Another BackUp Light Issue ~ Only this 1 is Switch Related ~ Have a Friends
>
> 87Westy @ My Place that I am doing a bunch of Stuff to & while moving it
> last
>
> night discovered that the B'U'Lights were not working ~ Bulbs checked out
> OK
>
> so I pulled the wires off the Switch, Jumped them & the Lights Worked ~
> Found
>
> Used Spare that I had & put a VOM to it to see if it was OK & it showed
> roughly
>
> 325 Ohms when pressed so figured it ought to pretty much be usable ~ Put it
>
> in & the B'U'Lights worked Just Fine ~ Decided to VOM the Old "Bad" Switch
> &
>
> was Quite Surprised when it showed a DeadShort when pressed ~ Decided to
>
> put it back in only to find that it Produced No Lights ~ Put My Spare back
> in & I
>
> get Lights ~ ReVOMed "Bad" Switch > DeadShort > Put It back In > No Lights
> ~
>
> My UsedSpare is now in place & the B'U'Lights are Working Nicely ~
>
>                                                         ORR ~ DeanB
>
>
> On 11 Apr , 2017, at 2:11 PM, David Beierl wrote:
>
> > Your voltmeter should be able to tell you where the problem lies.
> >
> > Yrs,
> > d
> >
> > On Tue, Apr 11, 2017 at 3:42 PM, Stuart MacMillan <stuartmacm@gmail.com>
> > wrote:
> >
> >> Yeah, DC circuits are famous for floating currents when grounds are
> >> disrupted.  I'll replace the ground wires and connectors and see what
> >> happens.
> >>
> >> Stuart
> >>
> >> -----Original Message-----
> >> From: Dennis Haynes [mailto:d23haynes57@hotmail.com]
> >> Sent: Monday, April 10, 2017 6:42 PM
> >> To: Stuart MacMillan; vanagon@GERRY.VANAGON.COM
> >> Subject: RE: Backup light puzzle anyone?
> >>
> >> You need to look at the grounds at one of the rear sockets. Resistance
> at
> >> the grounds is putting the 2 lamps in series from the other bulbs giving
> >> you
> >> the half voltage causing the low current sensitivity of the LEDs to
> light
> >> up.
> >>
> >> Dennis
> >>
> >>
> >> -----Original Message-----
> >> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf Of
> >> Stuart MacMillan
> >> Sent: Monday, April 10, 2017 9:09 PM
> >> To: vanagon@GERRY.VANAGON.COM
> >> Subject: Backup light puzzle anyone?
> >>
> >> I got a pair of LED back up "bulbs" along with the other LEDs for my '85
> >> automatic transmission Vanagon, and they are on all the time when
> ignition
> >> is on (other bulbs work fine). The switch on the selector is brand new
> >> (both
> >> parts), but there is a constant 5v at the backup lights and at the
> switched
> >> contact on the selector switch, and the proper 12 volts on the power
> side.
> >> 5v is enough to illuminate the LEDs.
> >>
> >>
> >>
> >> There has to be some kind of short in the wiring between the switch and
> the
> >> lights, but where would that wire pick up 5 volts?  The rear taillight
> >> light
> >> assemblies are in excellent condition and I've re-done the ground at the
> >> left taillight.
> >>
> >>
> >>
> >> I've had to go back to the filament bulbs until I can figure this one
> out.
> >> Or maybe just forget about the LEDs because the short is probably buried
> >> somewhere in the wrapped harness under the van.
> >>
> >>
> >>
> >> No end to the fun!
> >>
> >>
> >>
> >> Stuart
> >>
>
>