Cruise Control Fault Testing Test Box Procedure (03/87-953)

WARNING: This page is about the 900 S, 2D Hatchback, Automatic, which is a different variant/trim than selected.

Publication date: 1970-01-01
Reference number: 03/87-953

CRUISE CONTROL FAULT TESTING TEST BOX PROCEDURE

TECHNICAL SERVICE BULLETIN

Reference Number(s): 03/87-953, Date of Issue:

CHECKING CRUISE CONTROL SYSTEM WITH SPECIAL TEST BOX

APPLICATION

Model(s): 1984-87 Saab 900

All 900 Models with Hella Cruise Control

Issue: 03/87-953

File In: S.I. Man.

Vol: I

Section: A-3

Page: 103

SERVICE INFORMATION

A new test box has been introduced which aids in fault tracing the cruise control system on late 900 models and all 9000 models (Hella).

CRUISE CONTROL TESTER 85-80-078

The tester connects to the plug for the control unit and checks the vacuum pump and electrical switches. The procedure for the 900 and 9000 differ slightly so be sure to follow the directions closely. This was assigned as a required special tool and is being automatically shipped.

Fig 1: Cruise Control Text Box

TESTING INSTRUCTIONS

Unplug the connections from the control unit (one eight-pole and one single-pole and connect them to the tester.
Move the Cruise Control switch to, OFF and switch on the ignition. LED 1, 3 and 5 should light up.
900 Models - Led 5 should light up if car is moving or stationary.

9000 Models- LED 5 will not light up unless the vehicle is being driven.

FAULT-TRACING HINTS
- If LED 1 fails to light up, check the power supply to the control unit plug.
- If LED 3 fails to light up, check the pedal switches and wiring.
- If LED 5 fails to light up, check the speedometer sensor on the speedometer and its wiring.
Depress the clutch pedal. LED 3 should go out. Release the clutch pedal (LED lights up). Then depress the brake pedal, LED 3 should go out.
Fault-Tracing hints:
- Check the operation and adjustment of the corresponding pedal switch and wiring for short circuits.
Switch the Cruise Control switch to On. LED 9 should light up.
Fault-tracing hints:
- Check the switch and its wiring.
Depress the SET SPEED button.
900 Models - LED 2 and 6 will light up in two steps and stay lit while button is depressed.

9000 Models-LED 2 will light up and stay lit while button is depressed.

Fault-tracing hints:
- Check the switch and its wiring.
Depress the RESUME button. LED 6 should stay on as long as the button is depressed.
Fault-tracing hints:
- Check the wiring and it's switch.
Depress the button marked VENT on the tester. You should hear the Cruise Control pump "click" as it operates.
Fault-tracing hints:
- Check the valve and its wiring.
Depress the button marked PUMP on the tester. You should hear the pump operate.
Fault-tracing hints:
- Check the pump ant its wiring.
Depress the button marked PUMP and this time observe the throttle arm on the throttle housing. The throttle should open.
When the VENT button is depressed (or the clutch or brake pedal) the throttle arm should release.

Fault-Tracing hints:
- Check the vacuum system

If no defects are found during these tests and a cruise control fault still exists, the electronic control unit is probably defective.

WARRANTY INFORMATION

For warranty repairs, the above diagnostic steps are claimable using Labor Operation 36800. Include diagnostic step results in the claim technical explanation.