All about Ford Mondeo

Cooling system electrical switches and sensors - testing, removal and refitting
Cooling, heating, and air conditioning systems / Cooling system electrical switches and sensors - testing, removal and refitting


Note: Refer to the warnings given in Section 1 of this Chapter before starting work.

Coolant temperature gauge sender
Testing
1 If the coolant temperature gauge is inoperative, check the fuses first (see Chapter 12).

2 If the gauge indicates Hot at any time, consult the Fault finding section at the end of this manual, to assist in tracing possible cooling system faults.

3 If the gauge indicates Hot shortly after the engine is started from cold, unplug the coolant temperature senders electrical connector. If the gauge reading now drops, renew the sender. If the reading remains high, the wire to the gauge may be shorted to earth, or the gauge is faulty.

4 If the gauge fails to indicate after the engine has been warmed up (approximately 10 minutes) and the fuses are known to be sound, switch off the engine. Unplug the senders electrical connector, and use a jumper wire to connect the white/red wire to a clean earth point (bare metal) on the engine.

Switch on the ignition without starting the engine. If the gauge now indicates Hot, renew the sender.

5 If the gauge still does not work, the circuit may be open, or the gauge may be faulty. See Chapter 12 for additional information.

Removal
6 Unbolt the resonator support bracket from the engine compartment front crossmember.

Slacken the two clamp screws securing the resonator to the air mass meter and plenum chamber hoses, then swing the resonator up clear of the thermostat housing (see Chapter 4).

7 Drain the cooling system (see Chapter 1).

8 Disconnect the expansion tank coolant hose and the radiator top hose from the thermostat housings water outlet, then disconnect the metal coolant pipe/hose from the thermostat.

9 Unplug the electrical connector from the sender (see illustration).

6.9 Location (arrowed) of coolant temperature gauge sender
6.9 Location (arrowed) of coolant temperature gauge sender

10 Unscrew the sender and withdraw it.

Refitting
11 Clean as thoroughly as possible the opening in the thermostat housing, then apply a light coat of sealant to the senders threads.

Screw in the sender and tighten it to the specified torque wrench setting, and plug in its electrical connector.

12 Reconnect the hoses and refit the resonator, top-up the cooling system (see Chapter 1) and run the engine. Check for leaks and proper gauge operation.

Coolant temperature sensor Testing
13 Disconnect the battery negative (earth) lead (see Chapter 5, Section 1).

14 Unbolt the resonator support bracket from the engine compartment front crossmember. Slacken the two clamp screws securing the resonator to the air mass meter and plenum chamber hoses, then swing the resonator up clear of the thermostat housing (see Chapter 4).

15 Unplug the electrical connector from the sensor (see illustration).

6.15 Location (arrowed) of coolant temperature sensor
6.15 Location (arrowed) of coolant temperature sensor

16 Using an ohmmeter, measure the resistance between the sensor terminals.

Depending on the temperature of the sensor tip, the resistance measured will vary, but should be within the broad limits given in the Specifications Section of this Chapter. If the sensors temperature is varied - by removing it (see below) and placing it in a freezer for a while, or by warming it gently - its resistance should alter accordingly.

17 If the results obtained show the sensor to be faulty, renew it.

18 On completion, plug in the connector and refit the resonator.

Removal
19 Disconnect the battery negative (earth) lead (see Chapter 5, Section 1).

20 Unbolt the resonator support bracket from the engine compartment front crossmember. Slacken the two clamp screws securing the resonator to the air mass meter and plenum chamber hoses, then swing the resonator up clear of the thermostat housing (see Chapter 4).

21 With the engine completely cool, remove the expansion tank filler cap to release any pressure, then refit the cap. Provided you work swiftly and plug the opening as soon as the sensor is unscrewed, coolant loss will thus be minimised; this will avoid the draining of the complete cooling system which would otherwise be necessary (see Chapter 1).

22 Unplug the electrical connector from the sensor.

23 Unscrew the sensor and withdraw it. If the cooling system has not been drained, plug the opening as quickly as possible.

Refitting
24 Clean as thoroughly as possible the opening in the thermostat housing, then apply a light coat of sealant to the sensors threads.

Remove the material used to plug the sensor hole (where applicable), and quickly install the sensor to prevent coolant loss. Tighten the sensor to the specified torque wrench setting, and plug in its electrical connector.

25 Refit the resonator, top-up the cooling system (see Chapter 1) and run the engine, checking for leaks.

Coolant low level switch Testing
26 The switch is a reed-type unit mounted in the bottom of the cooling system expansion tank, activated by a magnetic float. If the coolant level falls to the MIN level or less, the appropriate bulb lights in the warning display.

27 If the bulb fails to light during the 5- second bulb test, check the bulb, and renew if necessary as described in Chapter 12.

28 To check the switch itself, unplug its electrical connector, and use an ohmmeter to measure the resistance across the switch terminals. With the float up, a resistance of 90 ohms should be measured; when it is down, the resistance should increase to approximately 150 kilohms.

29 If the results obtained from the check are significantly different from those expected, the switch is faulty, and must be renewed.

30 If the switch and bulb are proven to be sound, the fault must be in the wiring or in the auxiliary warning control assembly (see Chapter 12).

Removal
31 Disconnect the battery negative (earth) lead (see Chapter 5, Section 1).

32 Remove the expansion tank (see Section 7).

33 Unplug the switch electrical connector.

34 Release the switch by twisting its retainer anti-clockwise, then withdraw it.

Refitting
35 Refitting is the reverse of the removal procedure. Refill the cooling system (see Chapter 1). Start the engine, and check for coolant leaks when it is fully warmed-up.


2018 www.fordmon.ru. All Rights Reserved.