Aftermarket cruise control installation

Can you post a photo of the servo? I used to install a lot of Sears-branded units when I worked there in the 1980s. They had one model for less than a year that was a real piece of junk, but the less-expensive standard model was a dandy system and very reliable.

The first thing to look at is how the throttle cable is pulled. Most models do that by applying engine vacuum to the servo through some solenoid-controlled valves. You don't want to mount that inside the car. It is going to make repeated clicking or thumping sounds when the dump valve activates. It will buzz or vibrate to carefully adjust the throttle cable.

Also, there is no practical way to make the cable pull on the accelerator pedal. The location of the throttle return spring is irrelevant. The cruise control's servo is just doing the same thing the accelerator pedal cable does. If you can post a photo of the cable where it is attached to the throttle blade, that will help too. For those engines that used a quarter-round cable guide, they usually had two side-by-side. The second one was for the cruise control cable. The Sears unit, (was actually made by Dana Corp), came with a half dozen different connectors for the cable. One of those always fit every car I worked on. You must be careful to insure when you press the accelerator pedal while the cruise control is not engaged, that the cruise cable doesn't lift over and off the cable guide. That can result in very high engine speed.

There's also multiple ways the unit gets its speed signal. The Sears unit used a pair of magnets strapped to the front half shaft, or just one of them strapped to the rear-wheel-drive driveshaft. (Driveshafts spin three times faster than half shafts, so a single magnet generated enough pulses to keep the range of speeds it would engage at between about 32 to 85 mph.

They came out with a third model that connected to a vehicle speed sensor wire, but we didn't install a lot of them. For those, the unit will come with a booklet that listed the car models it will work on, where to fine the correct wire, and its color.

Some of the other brands of aftermarket cruise controls used a coil and metal core clipped around one of the spark plug wires. Those only held engine speed steady, not road speed.
That is fine with your manual transmission, but cars with automatic transmissions will lose speed going up hills, and gain speed going down. The Sears unit had a coil on a spark plug wire too, but it was only there to kick the system off if engine speed picked up too quickly, as in spinning on slippery roads or you bumped it into neutral.

Those other brands usually used real small-diameter wires. The Dana unit had fatter wires that were easier to work with. You'll need to attach two wires to the brake light switch. They gave us Scotch-Lok connectors for that, but those often caused intermittent problems. I always stripped the wires, then doubled them up to make them have a better connection. If either of those wires has an intermittent connection, the common complaint was the system would kick out when driving over bumps in the road. Mine never did that because I took the extra time with those connections.

We're all over the world, so we aren't familiar with your local shops. In my city we have one independent shop that is well-known for solving electrical problems.

The first photo shows the Sears / Dana system. The servo is the round black part in the center / bottom. This one is vacuum-operated, the same as most original equipment models.

The second photo showsa a Rostra system that appears to be real popular. The hardware kit is similar to what we had in the '80s. The red arrow is pointing to the throttle cable bracket that has to be fashioned to mount to the engine. The Sears unit had multiple other ways to anchor the cable's casing, but it had the same bracket and the same plastic grommet, (orange arow).

The third photo is what I found listed for the carburetor for your year and model. I also found references to injectors, so I don't know if you really do have a carburetor or a throttle body, but regardless, the blue arrow is pointing to the extra cable guide they used with the optional factory-installed cruise control. It is very unusual to see this cable guide laying horizontal on other car brands because when one cable pulls the throttle open, the other one is relaxed and could fall off. You'll notice these guides appear to be uncommonly deep, I assume to prevent that problem.

It's hard to see, but the orange arrow is pointing to the cable extension used with this type of cable guide. It looks rather short, so you'll have to see if that will work.

For pulling directly on the accelerator pedal, the Sears unit had a black plastic quarter-round snap-together bracket that could be bolted to the floor, then the bead chain is used as the cable extension and pulls on the pedal. We never used that because it was way too complicated and difficult to make it work right. If you're going to do it that way, you'll be smarter than me in that regard, and you'll have to be the expert who makes it work. I don't see that quarter-round bracket in the Sears photo, but there are definitely some parts missing. I don't see anything for this purpose in the Rostra photo either.

The Rostra unit doesn't use engine vacuum. That makes it nice for use with diesel engines that don't always have much vacuum. What concerns me though is how they pull the throttle cable. That can be done with a fast-acting electric motor, but it can also be done with an internal motor-driven vacuum pump. That is what they used on the Sears model I mentioned that lasted less than a year. (I mean it lasted as an inventoried item for less than a year). Those had a 100 percent failure rate of the pump assembly. Toward the end, we were sending our customers to Napa to buy the same Dana model cruise control package, with their name on the box), then we'd install it for them. No Sears employee tried to sell the miserable model to anyone. Also, if your unit is listed as it can mounted inside the car, it won't have a motor-driven vacuum pump. There's no way you would put up the horrendous noise those make.

It shouldn't be that bad. At Sears, their "standard of excellence" they held us to was 1 hour and 56 minutes for a cruise install and a two-wheel brake job to include rebuilding calipers or wheel cylinders. You'd think common sense would make that an even two hours, but some been counter came up with one hour, 56 minutes.

The majority of my cruise installs took closer to 2 hours and 15 minutes, and I didn't care. I took the time to be sure the wire splices were solid, the magnets wouldn't fly off, and the adjustments were perfect. Very few people came back with a complaint, which in the eyes of the leaders is a bad thing. They never yelled at the mechanics who had a lot of complaints because, in their words, "that was another chance to get the customer back in the store to buy something else".

At my next job as the suspension and alignment specialist at a very nice family-owned Chrysler dealership, I was never once yelled at for working too slowly, in my ten years there. My reputation was that it got fixed right the first time. Steering wheels were perfectly straight. Tire pressures were perfect, etc. The owners know it takes less time to do it right than to do it twice.

As a point of interest, by the early '90s there were still a lot of new cars showing up without factory cruise control, but to add it at the dealership was real easy. Bolt on the servo, attach the throttle cable, replace the brake light switch and steering wheel, and all the correct connectors were already hanging there or taped up in the right places. Just plug everything in and buzz off into the sunset.

Given the age of your car, before you start the install, may I suggest checking at the dealership or on eBay for an original kit for your car. My dealer gave me a half dozen kits that never got sold, and then they started robbing parts out of them. Those kits had been collecting dust for many years before that, so you never know what treasures you might find. At every dealership auction I go to, there are always a lot of "new old stock", (NOS) parts that people forgot about.

Don't let my two hours and 15 minutes throw you. That was after I had done many of them and knew exactly what to do and what worked best. A competent do-it-yourselfer would likely take the better part of a day for their first one.