Cruise control in a Thing (re-visited)

[mondshine]

Here’s another rant about cruise control.
After 12-15 years, the Audiovox vacuum operated cruise control in my Thing finally came to grief.
Although it passed all of the electrical tests, it was as dead as Julius Caesar.
Since Rostra took over the cruise control manufacturing from Audiovox, the CCS-100 kits are no longer available, so I went with the vastly superior all electric Rostra 250-1223, which I have installed successfully in a few other cars.
There are two major differences between the Rostra and the Audiovox units.
First, the Rostra is an all electric servo; meaning it does not require manifold vacuum to operate. The advantage is more accurate speed control under high load when manifold vacuum is not sufficient to pull the throttle cable.
The second major difference is that while the Rostra unit does have a tach signal connection, it is not used as a speed input. It only functions as an over-rev protection if the driver were to step on the clutch or shift into neutral while the cruise control was engaged. This means that a Vehicle Speed Sensor (VSS) is required. The VSS consists of a coil mounted in proximity to two magnets which are attached to an inner CV joint body.
Because this car already had cruise control installed, most of the wiring was in place, so this was a very easy swap.
Here are some photos (in case anybody wants to try this).

This is the servo mounted under the parcel shelf, next to the transaxle.

Under the rectangular grommet is a set of dip switches to "calibrate" the unit for the car.
The dip switches are set like this:

This plastic cover gives some protection from splash and rocks.

The coil & magnets "VSS" is mounted to two of the transaxle side cover studs.

The magnets are super glued to the CV body; spaced 180* apart after a very careful cleaning.

The cruise control throttle cable is routed through a rubber grommet into the engine compartment where it loops around to a secondary throttle arm on the throttle body.

There's a little trick with the secondary throttle arm. It uses a "barrel" like the regular throttle, but the cable is able to slip right through when the throttle is opened by the gas pedal.
Here, the throttle is closed:

Here, the throttle is opened (as if by the gas pedal):

Set up this way, the cruise control throttle cable can pull, but it cannot be pushed. This eliminates the possibility of the cable fouling or hanging up.

Anyway, the cruise control works very well. I "tested it" last weekend on a 120 mile freeway drive to a show south of Toledo, Ohio.
With some trepidation, I stepped on the clutch at 70 MPH with the cruise control engaged. the RPM increased by a couple hundred, and the cruise control immediately shut down.

So try this...you'll like it!
Mondshine

[KAmes]

I have an Audiovox unit on my old school bus/RV. Under some conditions 60 mph may be wide open throttle and the vacuum will suddenly give out. GM 427 with holley 4 barrel average measured 4 mpg. It's rear engine though! An electric unit interests me, using the same wiring would be important, control to servo is a 40 foot run. I may research this thanks for posting it. Sorry for the following non VW content. (it does have a beetle oil pressure switch in it)

[mondshine]

Kevin-
The wiring for both units is basically the same (some colors are the same, some different).

Here's the manual:
http://www.rostra.com/manuals/250-1223Form4565G.pdf

Since my servo and most of the wiring is in the back of the car, there are only four wires that run back to front. They are for the control switch.
Rostra wants you to power the system from the brake light fuse. That's because the system is active by a ground connection through the filaments of the brake light bulbs. When power is put to the brake lights, that connection to ground is interrupted, and the system switches off. So you need working brake lights for the cruise control to work. If your brake lights are LED's, you have to do a little trick with a relay, but it's no big deal.
The coil & magnet VSS is easy to do.
Having used both the vacuum operated cruise and the all electric servo, I can testify that the all electric servo is the way forward.
Good luck, Mondshine

[KAmes]

Thanks Gary, that sounds like it will work. Mine's the same with everything in the back and the bundle of wires to the control in the front. My brake lights are already on relays as I had trouble with the old wiring running the trailer light converter, so I can work that out. I can see why they did that, so a failure in a brake light bulb can't result in it being stuck on. Someday I'd like to devise an electric throttle pedal, there's a cable for that sucker if you can believe it.

[mondshine]

Kevin-
Just FYI, if you do go with an electric throttle (or drive by wire) there are Rostra kits that couple (electrically) to the throttle assembly so there is no servo at all.
Just a "brain" to control the throttle. That's how most modern cars do it.
Good luck, Mondshine