[T3] On my 73 square

Jim Adney jadney at vwtype3.org
Fri Sep 13 06:34:46 PDT 2019

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 

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 

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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