Electrical System Distribution Units

The previous system had reached a limit that made it difficult to enlarge the distribution system and functions. The Volvo 960 has therefore a new electrical system which also provides the following benefits:

- Greater reliability due to fewer cable harnesses and connectors among other factors.
- Relays and fuses more easily accessible.
- Better fuse protection of various power consumers.

These changes mean that all wiring diagrams have been modified and that fault tracing of certain functions has to be done in a partially new way.

On right-hand drive cars the fusebox in the passenger compartment is located on the right-hand side of the dashboard, other electrical distribution modules having the same location as on left-hand drive cars.

ELECTRICAL DISTRIBUTION MODULES
Main Fusebox
Located just behind the battery, the main fusebox contains eight 50 A main fuses. Fuse protection of supply cables directly from the battery gives the following benefits:
- Ensures that virtually everything in the car is fused.
- Better protection of the wiring in the event of a battery or wiring short-circuit in that the main fuse blows instead of the wiring melting.
- Allows a reduction of the cable cross-section on the supply cables from the battery.

If a main fuse blows, a number of functions usually disappear and this means that there is a serious fault in the form of a short-circuit that must be located and remedied.

In the case of certain major loads in the engine compartment, e.g., the engine cooling fan, the supply cable runs directly from a main fuse to the component. This means that the "fusible link" cable for the engine cooling fan is discontinued.

Relay - And Fusebox In The Engine Compartment
The box in the engine compartment contains relays and fuses for the majority of functions in the engine compartment. By having relays and fuses close to their loads, the number of cables that have to be routed into the passenger compartment is decreased. The majority of those relays that were previous distributed at a number of locations in the engine compartment have now been brought together in the new electrical distribution module. The goal was to use simple standard relays for as many functions as possible.

All relays for the electrically controlled functions in the engine compartment and the front are however not located here as certain relays have sensitive electronics, requiring a lower temperature environment, for example the main beam relay.

The box has room for 18 fuses and 13 relays. There is also a foglight jumper that allows simple control of the foglight function for the legal requirements of different markets, a service outlet to allow the starter motor to be operated and a 55-pin connection for joining the cable harnesses for the engine and the engine compartment.

The foglight jumpers come in two variants and are physically coded so that they can be connected in only one way.

The only separately fitted relay in the engine compartment is that for the engine cooling fan.

Relays
The relays with their respective locations in the form of letter designations are for the following components:
A Air pump
C Main relay, fuel system
F A/C compressor
G Foglights
L Foglights (only USA, have blue cover)
M Parking lights
N Horn
J Ignition coils
K Starter motor

Four of the 13 relay positions (B, D, E and H) are spare. Most of the relays are of the simple make-and-break type. The relay for the air pump and the fuel system has wider tab terminals since they conduct larger currents and should thus be able to dissipate heat better.

Fusebox In The Passenger Compartment
The fusebox in the passenger compartment has room for 24 fuses, five spare fuses, two automatic circuit-breakers and three relays. Its attachment is modified in that it is mounted on a bracket which is in turn screwed to the cowl. This provides better accessibility to the rear of the fusebox for fault tracing etc. Two of the relays in the fusebox are overload relays activated via the ignition key, depending on its position, and feed power to various consumers so that cables with reduced cross-sectional areas can be routed to the ignition switch. The third relay is for the fuel pump.

Relays
Relays in the fusebox in the passenger compartment.

X-supply, fuel pump and 15-supply

Central Relay Module In The Passenger Compartment
The central relay module in the passenger compartment brings together relays for most functions controlled from there, for example, the interval relay for the tailgate window wiper on station wagons is located by the rear bulb failure sensor. The central relay module is modified to allow room for relays with two relay bases since a number of twin-base relays have been added as: for cruise control, central locking and alarm. The central relay module has two panel sides in order not to occupy so much room. The attachment to the tunnel is modified so that it can be raised with a simple manual movement.

Relays
Relays that are common to the 850 have both figure and number designations.

In the central relay module, where the relay bases are physically coded and marked with letters there are:

Left Side:
A Timer relay, electrically heated rear window (also marked 208)
B-E Cruise control module (also marked 101-102)
D-G Central locking (205-206)
C-F Alarm (210-211)

Right Side:
H Belt reminder
L Interval relay windscreen wiper (203)
I Warning high catalytic converter temperature (207) (Japan only).

The other four relay positions (J, K, M and N) are empty.

A-, B- and C-Fuses
The main fuse is called the A-box, the relay-and fusebox, the B-box, the fusebox in the passenger compartment, the C-box and the central relay module in the passenger compartment, the D-box. The wiring diagram thus indicates the various fuses as, e.g., A2, B5 in order to designate fuse 2 in the main fusebox and fuse 5 in the relay-and fusebox in the engine compartment, respectively.