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Re: [T3] Tach signal


On 8 Jul 2006 at 18:52, shalom@ucla.edu wrote:

> Again, thanks for all your advise on the starter...my starter is 
> working.  Turns out that replacing some old fuses and replacing the 
> grounding strap from the battery to the frame reduced the voltage drop 
> to the solenoid.  I'm actually currently switching over to a ford 
> solenoid relay as an upgrade.  Just need to get some lower gauge wire.

There are no fuses in the starting circuit, so those changes didn't 
have anything to do with this, but improving the battery ground 
certainly could.

> I have a question about getting an RPM signal for a tach.  I have an FI 
> distributor so I have a connection with pins (21,12,22) that goes to 
> the computer.  Do I use either pin 12 and (22 or 21) to get the  RPM 
> signal?  Or do I get the RPM signal some other way (maybe like an 
> engine that is not FI)?  Does the distributor shaft turn 1 revolution 
> per 2 revolution of the crank shaft?

You don't want to make any connections to the FI wiring harness.

In general, the Tach RPM signal is taken from the ignition points, 
which is the negative side of the coil. That signal gives you 2 
pulses per crank revolution.

(Yes, the dist shaft turns at half the crankshaft speed.)

-- 
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

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