Re: throttle valve switch

[stans4@ix.netcom.com]

On 03/07/97 13:17:43 you wrote:
>
>
>Hi all:
>
>I have a '71 Squareback, and I've never been able to accuratley set my
>throttle valve switch as described in Muir's book.  '71 has the electric,
>not mechanical switch, so you can't hear it click.  I tried various
>combinations of pins on the switch with my volt-ohmeter and wasn't able to
>detect it going on and off.  I can, however, detect the switch going
>on/off several times as I advance the throttle by putting the
>volt-ohmmeter on a different set of connectors on the switch.  Am I
>missing something here in adjusting the cut-off?  I was hoping to hear
>from people with the similar switch in their T3.  My switch has 4
>connectors arranged vertically.  
>
>Which two connectors must you have the volt-ohmmeter on?
>
>Does the key need to be in the "on" position?
>
>Thanks,
>
>Doug H.
>'71 Squareback
>
>
>
I have a '71 and I use Muir's procedure to set mine.  I have a black label controller with a "D" suffix.  You have to have the ignition switch on when you do it, you are listening for a click as the contacts for the idle position come together(not in the switch!). At various times, when setting the thing after an engine replacemnt or overhaul, it won't click when I try to set it.  I have to get into the switch(4 screws on the corners) and clean contacts.  One time I found a bad solder joint.  This is a rare occurance.  If you take the cover off, you can see what's going on.  There's two sets of movable contacts, plus a pair of sliding contacts.  What the idea is is that the top pair of contacts signals the controller that the throttle is closed(where the click occurs). The other pair is for acceleration, when they are closed and the shaft is turning the other pair of sliding contacts gets dragged along and one goes over the sawtooth pattern on the base.  This pulses the inject!
!
ors and gives a little extra sho
t of gas, just like an accelerator pump on a carb.  So you want to make sure that the top pair is closed and making good contact when the throttle is closed and the bottom pair ISN'T making contact at closed position(confuses the hell out of the controller!).  Likewise at open throttle, the upper pair should be open.  With the key on in the ignition, you should be able to push the throttle arm and hear the injectors clicking away as you open the throttle if everything is set correctly.  To reiterate what Muir says, loosen screws top and bottom on the switch so it can move, swing the top away from you, towards the passenger compartment.  Then slowly rotate the top back toward you with the ignition on.  You should hear a click before it passes the half-way mark(long before).  One division more and then tighten down screws top and bottom.  On a couple of these switches I rescued from the scrapyard, I've had to do some pretty heavy degreasing, not sure why there was so much engine!
!
 oil in there.  I've also had to
 put new wires in them, not a real big job, but the old stuff was just too brittle.  If the throttle position switch isn't set right, the beast is very cantankerous, hard to start, sucks gas and has no pickup.  If you don't have the Bentley manual, only Muir, it can be kind of tough to trouble shoot the harness if you need to.  Muir has sort of a generic harness diagram, close enough to '71 for most purposes, but you really need the Bentley factory harness diagram to look for busted wires.  When I had this problem I made a check sheet for each component, started with the switch, then checked each wire in turn.  If it's not the switch, it's got to be a connector or harness wire, the controllers rarely fail.

Hope this long-winded whirl through the throttle position switch helps.