[T3] On my 73 square

[William Jahn]

I'm still trying to understand the head temp sensor. You said the crimp is
part of the threaded housing. Here you said " 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.

 What is the center conductor ?
I only see a thin red wire when all the black  plastic covering is removed
, I just see it in the crimp with nothing other than a thin black sleeve
over the red wire that can be pulled back. Since on early models if the
center conductor being bent shorts to the crimp then it's shorted to
ground. I get the steel crimp and the housing are to read 0 ohms. I thought
the wire from the sensor to the 1/4" female connector was the center
conductor. In another post you said there is a spring on each end of the
thermister / small puck was your term. My point is is I were to short the
lead anywhere from the connector to the crimp to ground then this is a
short to ground . You said from the connector to the crimp should read say
1.8K ohm . How is the center conductor insulated from each end of the puck.
Or is the puck or thermistor in contact with the crimp at one end via a
small spring and also contacts the body via a spring at the other end?

 I already tightened all the injector connectors and all the other ones the
TPS and MPS and trigger points. None of this made any difference.

On Fri, Sep 13, 2019 at 6:34 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 12 Sep 2019 at 16:47, William Jahn wrote:
>
> > I checked the spare from the connector to the crimp and did it several
> > times and got no ohm reading it was open as it should be.
>
> The crimp is part of the metal body, so from the connector to the crimp
> you
> should have read something like the 1.8 kOhms you got below. The crimp
> area is usually quite rusty, which might explain how you measured open
> (infinite resistance.)
>
> > I just now checked the one I had in the car and did it several times,
> > from the connector to the crimp I read 1.8k ohm , I also checked from
> > the connector the 1/4" female to the exposed wires that are not
> > touching the crimp and that was good no resistance. from the crimp to
> > the thread of the temp sensor I read 16 ohm.
>
> Again, from the crimp to the body should read zero Ohms, but this
> measurement really isn't important since the resistance from the connector
> to the threads is the only thing that counts.
>
> 1.8 k at room temp sounds just fine.
>
> >  I checked the air temp sensor cold 82*F 223 ohm let it run with the
> engine
> > cover in place and watched it after 20 minutes I read 108 degrees and the
> > lowest it got was 125 ohm . I drove once before and it was much hotter
> and
> > the low was 107 ohm the IAD temp measured on the area the sensor screws
> in
> > it  was close to 150 degrees.
>
> Sounds normal.
>
> >  Basically it seems the air temp sensor does not seem to drop low enough
> > fast enough
>
> If this is the problem, then why would disconnecting it (changing the
> resistance to infinite) seem to help.
>
> You've become fixated on the temp sensors, somewhat reasonably, because
> that's what you've found that makes a difference. But nothing you've
> measured there is actually out of order. OTOH, if one of those sensors has
> become intermittent, so that it's resistance jumps quickly back and forth,
> from
> normal to open, while hot, it's very likely that you wouldt never see that
> with
> your meter. For cases like this, substituting a different sensor is the
> only way
> to tell if the sensor is the problem.
>
> It's important to understand that the exact resistance is unimportant.
> There
> are very loose constraints on what is "correct" for them. As long as they
> are
> neither shorted (zero Ohms) nor open (infinite Ohms) they are fine.
>
> Have you checked the supply voltage from the relay while the problem is
> happening?
>
> Another thing you might check would be the tightness of each connection to
> the injectors. I've found that the male connector pins in later Bosch
> replacement injectors are very slightly thinner than the originals. This
> sometimes makes the connections poor, so that the injectors don't always
> open as far, or as long, as they should, resulting in missing or lean
> running.
> The Bosch tester will allow you to wiggle those wires while watching the
> resistance. If the needle jumps around when you wiggle the wires, you need
> to remove each female pin from the connector body and very gently squeeze
> it tighter. Check the fit on the injector before you put the pin back in
> the
> body.
>
> Fixing the tightness of all 8 injector pins will take a couple hours. It's
> a long,
> tedious, exhausting job, requiring plenty of patience.
>
> Consider contacting Phil to see if he's willing to let you visit him and
> have
> him test your system with the Bosch tester.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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