Sonett Cruise Control

Why would one want to install a cruise control in a Sonett, the whole point of which is driver involvement?

I would have asked the same question until a few weeks ago, when I twisted my right knee. It doesn't hurt as long as I keep it moving -- but holding the joint in a fixed position for long periods really makes it hurt.

That means that "fun" driving, with lots of throttle action, is no problem. But long highway drives are painful -- and nowadays, getting to fun-driving locations (autocrosses, racetracks, and winding backroads) often involves a long highway drive first.

Suddenly cruise control made sense. A tip on the Vintage SAAB forum suggested the Audiovox CCS-100, an aftermarket unit sold through some Autozone stores and various online retailers for about $100.

A little Internet research (try typing 'Audiovox cruise control' into a search engine) showed me that this unit has been installed successfully on everything from Miatas to Volkswagen vans to motorcycles -- so I figured that there should be no problem making it work on a Sonett.

As it turns out, I was half right. It works... but it wasn't exactly "no problem"...

As with most engine work on a Sonett III, the job is much easier if you start by removing the engine lid completely.

The Audiovox kit consists of: a vacuum servo unit; a small control panel; some parts for installing a magnetic speed sensor; a bag of assorted installation hardware; an assortment of hoses and electrical connectors; and three separate reference instruction manuals.

Although I salute Audiovox's effort to provide everything that might be needed, all the pieces do make the job seem a bit intimidating. As it turns out, most of the parts aren't needed to install the unit on a Sonett.

The heart of the cruise control is this vacuum-operated servo unit, which has its electronic control module built into the back end.

The servo unit is about the size of a standard oil filter (as opposed to a Sonett oil filter.) It has a mounting bracket attached to its bottom side, about three feet of actuator cable sticking out one end, a vacuum connection on the top, and an electrical panel on the opposite end from the cable.

A small plastic cover, secured by two screws, hides this circuit board on the end of the servo. At the top you see the seven numbered switches that set up the electronics.

They're tiny -- so you want to set them before you start putting parts on the car, while they're easy to reach!

The installation manual makes the switch settings seem very complicated, with a lot of detail about the Vehicle Speed Sensor (VSS) and installing the magnet kit. As it turns out, NONE of this is necessary on a Sonett -- it only applies to cars with automatic transmissions and/or electronic engine management systems. Here's how to make the settings you do need:

Jumper block: To the left of the numbered switches, there's a small black jumper that connects two pins together. Remove it; this tells the system you've got a manual transmission.

Switches 1 and 2: These program the "pulses per mile" setting delivered by the VSS. Since we don't need a VSS, it shoulding matter how you set them -- but it does! Set both of them to ON ("up" position, away from the number.) This is shown in the table as the setting for 8000 PPM. If you set it for a lower number, the cruise control won't lock in at higher speeds.

Switch 3: Set it to OFF. This tells the system you don't have a VSS, and it should sense the vehicle's speed by measuring engine RPM only.

Switches 4 and 5: These control "sensitivity," or how drastically the servo responds to speed changes. This lets you tailor the system's response depending on the vehicle's horsepower and weight. For a stock Sonett, the "medium" setting works fine, so set both switches to OFF.

Switch 6: This programs the unit for the type of control switch you'll use. The switch supplied in the kit is a normally-open type, so set this switch to OFF.

Switch 7: This tells the cruise control whether the speed signal is coming from an engine control module (ECM) or a connection to the ignition coil. The Sonett doesn't have an ECM, so we'll use the coil connection; set this switch to ON.

That's all for the switch settings. Leave the cover off for now; you'll be making connections to the circuit board later.