If the system will accelerate but does not hold speed at all the problem is generally a faulty amplifier. If the system holds but the speed drops off the amplifier needs remanufacture.

If the system will not accelerate, the problem could be the amplifier, bad brake light bulbs, bad wiring or connections, a bad switch (on the steering column), a broken actuator cable, a bad actuator, or insufficient vacuum to the actuator. A gross test may be performed on the actuator by applying about 12 inches of vacuum to the actuator and quickly connecting a small 9 Volt battery across the terminal. Touch the lead quickly; do not leave the voltage applied for more than a fraction of a second. Try the opposite polarity as well. You should see the actuator cable move in one direction and then the other.

Once the system is holding speed reasonably well, it may be susceptible to surging, either mild or moderate.

Usual complaints with this system are two types of surges:

• Hunting several mph - this is caused possibly by the amplifier but not necessarily! Other problems can cause this including a faulty speed transducer (near the speedometer or cable) or vacuum problems (see below.) If the amplifier has been remanufactured by us it has been road tested a minimum of three (3) miles and from ten to a couple hundred miles if necessary. Therefore, the rest of the system must be checked. The problem usually lies elsewhere.

• Speedometer is steady and the system holds well but you feel an occasional surge (especially when encountering a bump in the road) or you can "feel" the system working. This seems to be normal with these systems. Don’t forget that this is 1960’s technology. The newer systems, from 1981 until present, are sensitive but not as quirky. See below for other suggestions.

Some Road conditions can cause almost any cruise system to appear to have strange reactions. The best test for surge is on a very smooth, very flat road that is several miles long.

If the amplifier has been remanufactured (by us), look for:

• pin-holes, cracks in vacuum lines

• faulty vacuum check valves

• sticky throttle linkage

• sticky actuator cable (probably should be replaced) - the white plastic sheath wears

• bad actuator (especially if it drops several miles per hour on "accel/set")
  there is a gross test that you can do to see if there is any actuator function at all

As always in engineering and electronics there is a possible trade-off: we can make the amplifier less responsive but this diminishes the accuracy of the system. It will not hold speed as well on grades.

Another suggestion is that, although all of the 10-pin amplifiers can be used interchangeably, there are differences. The 001 545 70 32 (for manual transmissions) has a different circuit from the 001 545 20 32, 001 545 21 32 and 002 545 37 32. It is more similar to the circuits used in the Porsche 928 amps. The 001 545 21 32 was designed for the diesels and is more quickly responsive, especially on "resume." There have been instances of surging when used with the more powerful engines. The 001 545 20 32 was used primarily with the V-8 engines, the turbo diesels (116 bodies.) The circuit in the 001 545 20 32 is a little more "surge-resistant."

We are glad to bench test and road test an amplifier. Please e-mail or call for current test service fees.

General Development Laboratories
121 Easter Street
Morro Bay, CA 93442

805 772-5588