SERVICE MANUAL UPDATE SEC. 8A A/C COMPRESSOR CONTROLS DIAG.. Geo Prizm 1989

For 1990-2009 cars

# SERVICE MANUAL UPDATE SEC. 8A A/C COMPRESSOR CONTROLS DIAG.

#### Subject: AIR CONDITIONING COMPRESSOR CONTROLS SYSTEM DIAGNOSIS

#### Model and Year: 1989-90 GEO PRIZM

In the 1989/90 GEO Prizm Electrical Diagnosis Service Manual Supplement (ST373-89/90 EDM), the Air Conditioning Amplifier Engine Speed Input circuit (Figure 1) was not diagnosed in the System Diagnosis Chart in the Air Conditioning cell (Cell 64). Step A19 (Figure 2) should replace step A19 in the System Diagnosis Chart on page 8A-64-7. In addition the following steps; A28 - A31 (Figure 2) should be added to the end of that chart on page 8A- 64-8.

#### SYSTEM DIAGNOSIS

AIR CONDITIONING: COMPRESSOR CONTROLS DIAGNOSTIC CHART A (AMENDMENTS)

TEST RESULT ACTION -------------------------- -------------------- -------------- A19. Connect a digital More than 0.3 ohms. Repair open in multi meter from A/C WHT/BLK wire AMPLIFIER connector between A/C cavity 10 to chassis Less than 0.3 ohms. AMPLIFIER and ground. Measure JUNCTION BLOCK 4. resistance. GO TO A28.

A28. Start engine. Back- Tachometer indicates Replace AIR probe AIR CONDITION- correct engine speed. CONDITIONING ING AMPLIFIER con- AMPLIFIER. nector with a tacho- Tachometer does not meter from cavity indicate correct GO TO A29. 14 to chassis engine speed. ground. Measure engine speed.

A29. Disconnect IGNITER con- More than zero volts. Repair short to nector and AIR CON- voltage in BLK DITIONING AMPLIFIER wire. connector. Connect a Zero volts. GO TO A30. digital multimeter from IGNITER connector cavity 4 to chassis ground. Measure voltage.

A30. Connect a digital Less than infinite. Repair short to multimeter from ground in BLK IGNITER connector wire. cavity 4 to chassis Infinite. GO TO A31. ground. Measure resistance.

A31. Connect a digital More than 0.3 ohms. Repair open in BLK multimeter from wire between IGNITER connector IGNITER and AIR cavity 4 to AIR CONDITIONING CONDITIONING AMPLIFIER. AMPLIFIER connector cavity 14. Measure Less than 0.3 ohms. A fault exists resistance. within the IGNITER or the ignition system. Refer to Driveability and Emissions Section 6E of the 1989/90 Geo Prizm Service Manual (ST373-89/90) for system diagnosis.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.