[T3] I asked a question few days ago on a TVS switch.

Jim Adney jadney at vwtype3.org
Sat Nov 4 09:50:28 PDT 2017

On 3 Nov 2017 at 12:04, William J wrote:

>  What I'm asking is On later TVS there is a spring loaded center
> pivot.( wave washers and it's pressed into the TVS base plate. 
>  Whether you have the stop or not , from what I can tell with a TVS
> mounted to a spare throttle body /IAD . The resistance of the spring
> loaded center pivot is all that holds the adjustment where you set it.

I don't think the wavy washer on the center pivot has any effect other than 
keeping things from rattling around.

>  Jim . In the adjustment info you sent on how to adjust them and the
> three different generations.You said even some late ones didn't have
> the stop and ones that do you adjust to the stop and lock it down
> there. Is this proving that the stop is set so the wipers are right at
> the point of being on the idle pad and the enrichment wiper right on
> the edge of moving from board # 20 contact to # 9 . Also just before
> the wipers move the on/off switch should hit the on position just
> before or at the same time the wipers move. 

My assumption has always been that Bosch added the internal stop, which 
they adjusted at the factory, so that, yes, it would position the switch 
proberly, without the need for a VOM or the Bosch FI tester.

>  I ask because if the throttle has wear where it seats closed a bit
> further then the stop on the TVS used as an adjustment will become the
> stop allowing more air through the throttle being slightly open.

I agree that the throttle plate is bound to wear into the throttle bore. And, 
yes, this will slowly cause the internal stop, if yours has one, in the TVS to 
stop the throttle plate. Yes, it probably makes sense to check this adjustment 
every 100,000 miles or so. That wear is very slow, but it's likely that it wears 
faster at first, then slows down. So check it at 50,000, then at 150,000, 
250,000, etc.

Keep in mind that NONE of the OE TVSs came with the internal stop. The 
internal stop was a later innovation that Bosch only added to later 
replacement parts.

>  If you adjust to the stop of the TVS and don't factor in the 2 degree
> marks what this means to me is if a stop were bent I would need to
> mount the TVS hold the throttle closed rotate the TVS until the wipers
> are in the location I described above then bend the stop so the
> plastic arm just touches. 

Yes, it would be hard to reset the internal stop if it had gotten bent. I'm sure 
Bosch had a jig to make it easy to set them. but we don't.

>  Does this make sense? I have no idea based on slight difference in
> throttle bodies even when new how new TVS stops were adjusted to work
> unless it was close enough .

It's not a critical adjustment. You just want the TVS to close the idle contact 
when you let up on the throttle and open that contact quickly as soon as you 
give it some gas. The weak link in this chain is any stickyness in the throttle 
pedal or cable. If anything sticks and doesn't come all the way back when 
released, the TVS won't close the idle contact. I think this is the only reason 
VW/Bosch suggested the 2 deg extra motion. That just gives it a bit of extra 
leeway to close even if the pedal or cable doesn't come all the way back.

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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