All about Ford Mondeo

Fuses, relays and timer module - testing and renewal
Body electrical system / Fuses, relays and timer module - testing and renewal

Note: It is important to note that the ignition switch and the appropriate electrical circuit must always be switched off before any of the fuses (or relays) are removed and renewed. In the event of the fuse/relay unit having to be removed, the battery earth lead must be disconnected. When reconnecting the battery, reference should be made to Chapter 5.

1 Fuses are designed to break a circuit when a predetermined current is reached, in order to protect components and wiring which could be damaged by excessive current flow.

Any excessive current flow will be due to a fault in the circuit, usually a short-circuit (see Section 2). The main fusebox, which also carries some relays, is located inside the vehicle below the facia panel on the passengers side, and is accessed by a lever behind the glovebox (see illustration).

3.1 Main fusebox layout
3.1 Main fusebox layout

1 Fuse/relay removal tweezers 2 Diode
3 Multi-plug connections

2 A central timer module is located on the bottom of the main fusebox. This module contains the time control elements for the heated rear window, interior lights and intermittent wiper operation. The module also activates a warning buzzer/chime when the vehicle is left with the lights switched on, or if a vehicle fitted with automatic transmission is not parked in position P.

3 The auxiliary fusebox is located on the front left-hand side of the engine compartment, and is accessed by unclipping and removing the cover. The auxiliary fusebox also contains some relays (see illustration). Each circuit is identified by numbers on the main fusebox and on the inside of the auxiliary fusebox cover. Reference to the fuse chart in the Specifications at the start of this Chapter will indicate the circuits protected by each fuse.

Plastic tweezers are attached to the main fusebox and to the inside face of the auxiliary fuse and block cover, to remove and fit the fuses and relays.

3.3 Auxiliary fusebox layout
3.3 Auxiliary fusebox layout

1 Fuses 1 to 3
2 Fuses 4 to 8, 11 to 14 3 Relays R2, R5 and R6
4 Relays R7 to R11
5 Relay sockets for relays R1 and R4 6 Diode

4 To remove a fuse, use the tweezers provided to pull it out of the holder. Slide the fuse sideways from the tweezers. The wire within the fuse is clearly visible, and it will be broken if the fuse is blown (see illustration).

3.4 The fuses can be checked visually to determine if they are blown
3.4 The fuses can be checked visually to determine if they are blown

5 Always renew a fuse with one of an identical rating. Never substitute a fuse of a higher rating, or make temporary repairs using wire or metal foil; more serious damage, or even fire, could result. The fuse rating is stamped on top of the fuse. Never renew a fuse more than once without tracing the source of the trouble.

6 Spare fuses of various current ratings are provided in the cover of the auxiliary fusebox.

Note that if the vehicle is to be laid up for a long period, fuse 34 in the main fusebox should be removed, to prevent the ancillary electrical components from discharging the battery.

7 Relays are electrically-operated switches, which are used in certain circuits. The various relays can be removed from their respective locations by carefully pulling them from the sockets. Each relay in the fuseboxes has a plastic bar on its upper surface to enable the use of the tweezers. The locations and functions of the various relays are given in the Specifications (see illustration).

3.7 One-touch down window relay in the drivers door
3.7 One-touch down window relay in the drivers door

8 If a component controlled by a relay becomes inoperative and the relay is suspect, listen to the relay as the circuit is operated. If the relay is functioning, it should be possible to hear it click as it is energized. If the relay proves satisfactory, the fault lies with the components or wiring of the system. If the relay is not being energized, then either the relay is not receiving a switching voltage, or the relay itself is faulty. (Do not overlook the relay socket terminals when tracing faults.) Testing is by the substitution of a known good unit, but be careful; while some relays are identical in appearance and in operation, others look similar, but perform different functions.

9 The central timer module located on the bottom of the main fusebox incorporates its own self-diagnosis function. Note that diagnosis cannot take place if the heated rear window is defective.

10 To activate the system, press the heated rear window button while the ignition is being switched on, then release the button. Operate the light switch, washer pump switch and all of the door switches one after the other, and check that the buzzer confirms that the input signals are correct.

11 Now move the wiper lever to the intermittent wipe position, and check the output signals by operating the same switches.

12 The self-diagnosis function is turned off by switching the ignition off and on again.

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