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RE: [T3] Orphan FI Thermo Switch?


On 9 Apr 2001, at 18:43, Fuhriman, Mark wrote:

> My engine # is U0478258.  

That's a late 71.

> > You should just remove the temp switch, and run the wire to the
> > solenoid terminal that is hot ONLY while the starter is
> energized.
> 
> Let me make sure I'm with you:  On my car, wire #18 should run
> directly from the ECU to terminal 50 on the starter solenoid.

I've never managed to memorize the German wire # system, but if 
50 is the one that comes from the ignition switch, then that's the 
one.

> I haven't actually traced that wire yet, but I thought (I guess
> wrongly) based on the wiring diagram that my thermo switch was
> connected directly to the starter solenoid.  But now I am guessing the
> other end of that wire is on the ECU.

IIRC, the plug on the ECU has 25 pins. Wires # 1-25 go to pins 1-
25 respectively. Wires that don't lead directly to the ECU are given 
numbers above 25.

> So what kind of information is my thermo switch giving the ECU
> under the current arrangement?  And what kind of information is
> *supposed* to be traveling through wire #18?  Thanks for the help!

Currently pin 25 on your ECU is floating unless the temp is below 
the trip point of your temp switch, in which case it is grounded. 
That wire is supposed to be 12V while starting (to give a little extra 
gas at that time) and grounded thru the solenoid at all other times.

What you have right now MAY be fine. It all depends on the 
circuitry inside the ECU. I don't know what state the ECU thinks 
the wire is in if it is allowed to float.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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