CODE AU ACC I

With everything connected, check the power at pin 22 of the ACC control unit (The thing in the dash with the display) It will pop out by removing the ashtray, reaching in the hole and pushing the ACC unit out from behind. The voltage at pin 22 varies according to what speed is selected.

SPEED 1 .8V
SPEED 2 2V
SPEED 3 5V

As you select different speeds, the voltage should change. If these voltages aren't close and varying with different speeds, the control unit is bad.

If the readings are normal, disconnect the unit (turn key off first), check continuity between pin 22 of the control unit and pin 2(Blue wire) of the transistor unit (speed controller). The controller is located on the evaporator box, under the right plastic cover in the engine compartment near the windshield. Its connector on cars -88 is easily accessed by removing the cover, even though the actual controller lies deeper. There will be two similar connectors, one to the controller, one to the receiver drier pressure switch. On 88- cars the connector goes directly to the controller, there is no "pigtail" off the controller. You may have to remove the false bulkhead partition to get to the connector. One 12 mm bolt on the right side and one 25 Torx screw on the left side holds it down. It fits in a groove rather snugly and may take a bit of force to pull up. All the controllers sit down in the evaporator, held by four 10 Torx screws. They are black boxes about 4" X 4" in size.

The voltage measurement makes sure what the control unit tells the transistor, gets there. You check pin 2 of the transistor for the same readings you got at pin 22 of the control unit when changing the fan speed.

Pin 1(Green wire) at the transistor should be battery voltage with the key on. If not check fuse 6.

Jumping pins 3 and 4 of the transistor, with the transistor disconnected, should run the fan. If the fan runs, the transistor is bad. If it doesn't, go directly to the fan connector under the center and left covers. It should receive voltage when the key is on. If not, check fuse 6. If the fan has power and you ground its ground pin directly, and it runs, you have a wiring problem between the controller and the fan on the ground circuit. If not, the fan is bad. Make sure you are checking the fan wires, not the air box temperature sensor. The temp sensor has red wires, the fan a green wire and a black wire, both of larger gauge than the temp sensor.