Jacobsen AR3, Technical/Repair Manual

Page: 83 / 342

4-26 4181384 First Edition
ELECTRICAL
4
Glow Plug Circuit—Theory of
Operation
When the key switch is turned and held in the glow
position, voltage is available from key switch terminal 19
to glow plug wait light H1. Current also flows from key
switch terminal 19 to glow plug timer terminal 4, turning
on the timer.
With the glow plug timer on, a ground is provided from
glow plug timer terminal 6 to the glow plug wait light,
turning on the light for approximately 5 seconds.
Unswitched power is available to glow plug relay terminal
30 from 40-amp fuse F12. While the key switch is held in
the glow position, current also flows from key switch
terminal 19 to glow plug relay terminal 86, energizing the
relay. With the relay energized, current flows between
relay contacts 30 and 87 to the glow plugs, heating the
glow plugs.
When the wait light goes off, the operator turns the key
switch to the start position to crank the engine. With the
key switch in the start, position current continues to flow
from key switch terminal 19 to the glow plug circuit. The
glow plugs continue to heat until the key switch is
released to the run position.
If the key switch is turned to the start position before the
glow plug wait light times out, the start circuit will cancel
the wait light circuit. (See “Start Circuit—Theory of
Operation” on page 4-29.)