Edc-Components In Electrical Distributor Unit; Relay Box - Volvo DH10A 245 Service Manual

EDC-components in electrical distributor unit

Relay box 3060

Relay box
Relay box 3060 contains relays for voltage feeding the
system and three small electronic circuits, which main-
ly contain transistors. Normal voltage feed, from fuse
45, comes in to pins 1 and 9. At input to R1, there is a
diode that prevents reverse current. Before R1 can
close, TR1 must open, which it does at a (+) via 3063
relay (engine shut-off). This (+) also closes R2. On the
strength of the power available, R2 distributes the feed
to the two lines going to the control unit.
Electronic circuit TR3 converts engine speed sensor
(753B) impulses, which vary between –12V and +12 V
up to pin 15, to a pulse signal from 0–24V, which is fed
to pin 32 in the control unit. Pin 14 is earthed.
"+" "+" above
in N-pos. 3 km/hr
"–"
when p-brake
is applied
148
Fuse 45 for Fuse 44 for
normal voltage cruise control
feed stalk
+30 from
coupling box
Relay 3063
breaks "+"
when engine
stops
TR2 circuit is wired to the automatic transmission and
parking brake. Its function is to simulate "clutch pedal"
up. It must be possible, namely, to earth pin 27 on the
control unit, even if the hus has automatic transmission
and thus does not have a clutch pedal. "+" in the N-
position is used when the bus is stationary and gives
(–) on pin 6 when the parking brake is on. "+" above
3 km/h is converted by the TR2 circuit to (–) on pin 6
during driving.
With no voltage at pins 1 and 9, relay R1 remains in the
inactive position and voltage is fed instead from pin 10.
The TR4-circuit then lights warning lamp EDC+ by
giving a (–) at pin 11.
Control unit 9058
Control unit 9058