Checking the Air Conditioning (A/C) System
Activating relay
- Ignition on.
Activate the air conditioning (A/C) relay. One of the following combinations of "clicking sounds" should be heard from the relay and air conditioning (A/C) compressor clutch.
1. Neither the relay nor clutch click.
2. The relay clicks but not the clutch.
3. The air conditioning (A/C) clutch and relay click. Select one of the alternatives above.
Alternative 1:
^ Proceed to next step below.
Alternative 2:
^ Proceed to Checking power cable section below.
Alternative 3:
^ Proceed to Checking cable section below.
Checking power cable
- Ignition off.
- Disconnect air conditioning (A/C) relay.
- Ignition on.
Connect a voltmeter between relay base terminal 1 and ground.
The voltmeter should read battery voltage.
If reading is OK:
^ Proceed to next step below.
If reading is incorrect:
^ Proceed to Checking power supply section below.
Checking for an open-circuit
Check cable between air conditioning (A/C) relay terminal 2 and engine control module (ECM) #B40 for an open-circuit. Was a fault detected?
Yes:
^ Proceed to Corrective action section below.
No:
^ Proceed to Replacing component section below.
Checking power supply
Check cable between system relay (2/32) terminal 3 and air conditioning (A/C) relay terminal 1 for an open-circuit. Check fuse 11 B/5.
If the fuse is blown, check the circuit after the fuse for a short-circuit to ground.
Then continue with:
^ Operation done
Checking power cable
- Ignition off.
- Disconnect air conditioning (A/C) relay. Connect a voltmeter between relay base terminal 3 and ground.
The voltmeter should read battery voltage.
If reading is OK:
^ Proceed to next step below.
If reading is incorrect:
^ Proceed to Checking power supply section below.
Checking air conditioning (A/C) relay
- Ignition off.
- Reinstall the air conditioning (A/C) relay.
- Disassemble the 1-pin compressor connector.
- Connect a voltmeter (Fluke multimeter) between the connector (relay side) and ground.
- Ignition on.
Activate the air conditioning (A/C) relay. When the relay switches the voltmeter should read battery voltage.
If reading is OK:
^ Proceed to Checking clutch section below.
If reading is incorrect:
^ Proceed to Checking for an open-circuit section below.
Checking power supply
Check cable between fuse 110/5 and air conditioning (A/C) relay terminal 3 for an open-circuit.
Check fuse 11C/5.
If the fuse is blown, check the circuit after the fuse for a short-circuit to ground.
Then continue with:
^ Operation done
Checking clutch
Defective thermoswitch or compressor clutch. Remedy as necessary.
Then continue with:
^ Operation done
Checking for an open-circuit
Check cable between relay terminal 5 and the compressor for an open-circuit. Was a fault detected?
Yes:
^ Proceed to next step below.
No:
^ Proceed to Replacing component section below.
Corrective action
Remedy as necessary.
Then continue with:
^ Operation done
Replacing component
Try a new air conditioning (A/C) relay.
Then continue with:
^ Operation done
Checking cable
- Ignition off.
- Disconnect the pressure switch (Pressostat) (7/53) connector.
- Blower fan at low-speed.
- Air conditioning (A/C) switch on.
- Start engine.
Connect a voltmeter between pressure switch (Pressostat) terminal 1 and ground.
The voltmeter should read battery voltage.
If reading is OK:
^ Proceed to next step below.
If reading is incorrect:
^ Proceed to Checking for an open-circuit and short-circuit section below.
Checking pressure switch (Pressostat)
- Ignition off.
- Pressure switch (Pressostat) disconnected.
Connect an ohmmeter across both pressure switch (Pressostat) terminals.
The ohmmeter should read approx. 0 ohm.
If reading is OK:
^ Proceed to Checking for an open-circuit and short-circuit section below.
If reading is incorrect:
^ Proceed to Checking the air conditioning (A/C) system section below.
Checking for an open-circuit and short-circuit
Check cable between the pressure switch (Pressostat) terminal 2 and engine control module (ECM) B25 for an open-circuit, and for a short-circuit to ground. Remedy as necessary.
Then continue with:
^ Operation done
Checking for an open-circuit and short-circuit
Check cable between ECC control module terminal A3 and pressure switch (Pressostat) terminal 1, (MCC unit terminal B22 and pressure switch (Pressostat) terminal 1), for an open-circuit, and for a short-circuit to ground.Remedy as necessary.
Then continue with:
^ Operation done
Checking the air conditioning (A/C) system
Check pressure in the air conditioning (A/C) system.
Then continue with:
^ Operation done