[T3] On my 73 square

William Jahn willjahn975 at gmail.com
Thu Sep 12 10:40:58 PDT 2019

Interesting--- I only read about the spring contact never thought about the
crimp or what might seal out water. One I have that reads real high yet is
not shorted and I used it for a while yet the connector was broken off I
just soldered on another connector. All it has now is a red wire and a bit
of a black sleeve that fits into the crimp which I assume is what insulates
the wire from the crimp and maybe seals out water. I read someplace that
they were filled with some sort of paste that dries hard. I imagine the
plastic tube is there to prevent wire flex to prevent the wire from
breaking at the crimp.

 I  looked at the one aftermarket replacement that URO Parts makes and many
sites sell like J Bugs and it does not have the steel crimp just a thick
short black plastic tube with the wire through it and a sort of heat shrink
cover that is easy to slide up. From the looks of it it's not made the same
way at all other than the hex head and threaded section is all one piece.
Bus Depot claims theirs is stainless steel and cheaper and better than the
original yet the photo they offer looks the same as the one I got and they
stress if you order it may not be the same one it will be what's available
at the time.

 I've no idea what keeps moisture or water out of the original ones or if
water does enter if it can corrode the springs or simply change resistance
because water/moisture is a conductor of sorts.

 Since the one in my car varies and the insulation break is about 1/8" from
the crimp water would not need to get inside all it needs is water to be on
the strands  and contact the metal crimp. As I said I have no idea what
seals the unit from water getting inside all I see is a thin plastic tube
over the wire insulation into the crimp. So there is the wire insulation
and that black tube over the insulation into the crimp.

 I can't hurt to try the spare I have since none of this has been
compromised. Since there is no way to monitor the head temp sensor other
than unplugging and checking cold then doing the same when hot . Or set it
in cooking oil and raise the temp , read the temp and compare with an ohm
meter connected what ohm reading at temp changes. I've read both sensors
are calibrated @68*F and found what they should read at that point and then
the graphs with their curve + or - 10 %.

On Thu, Sep 12, 2019 at 5:24 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 11 Sep 2019 at 21:10, William Jahn wrote:
> >  I do know the head temp sensor in the car now does not always read the
> > same resistance at the same temp and when I removed it I could see a
> > dark area under that whitish plastic cover and when I pulled the cover
> > back I could see an area just above the top of the sensor where the
> > insulation was one , no broken strands yet they were dull copper not
> > bright clean so perhaps that might cause an issue .
> The missing insulation won't cause a problem unless it allows the center
> conductor to short to ground on the steel crimp. That will bring you to a
> halt
> very quickly, but is seldom a problem except on the '68-9 cars where that
> sensor is cramped under the #4 exhaust port. On those engines the wire is
> forced to make a hard right angle turn just past the crimp, and they can
> short
> there.
> Surface corrosion on the copper strands won't add enough resistance to be
> measurable to your instruments, or to matter to our FI. If water has
> gotten
> down into the sensor element itself, that could cause an increase in
> resistance, or an intermittent problem, because the sensor element is just
> a
> tiny little puck with contact made by spring pressure on each end.
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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