Larry, I believe the lever handles (OK Scott?) with the enlarged "knobs" that you have on your '91 may be replacements.  At least my '91 does not have them, except for one, which I recently put on after breaking an original.  mcneely

---- Larry Alofs <lalofs@GMAIL.COM> wrote:
> Speaking of heater controls and little known features.  Two of the heater
> control levers have bumps on the sides of the 'knobs".
>   This can help you find the right one while keeping your eyes on the road
> or when it's dark.  They are more prominent on the later model vans.  I
> didn't notice them until I got my '91, tho they were there on two earlier
> vans.
>   Maybe everyone else already knew this...
>
> Larry A.
>
>
> On Mon, Nov 19, 2012 at 7:43 AM, Mike S <mikes@flatsurface.com> wrote:
>
> > On 11/18/2012 10:27 PM, MICHAEL H wrote:
> >
> >> Harry - pneumatic tires ARE shock absorbers at a basic, technical level
> >> ...
> >>
> >
> > Well, no. They're more like springs, any ability tires have to absorb
> > energy is minimal compared to an actual shock absorber, and is something
> > tire makers try to keep to a minimum for energy efficiency. Shock
> > absorbers are dampeners, made to absorb energy from movement.
> >

--
David McNeely