Electrical Maintenance (Rev. 12/03)
36
GLOW PLUGS
Glow plugs heat the combustion chamber to aid in quick
starting. The glow plugs are energized when the Preheat-
Start switch is held on the PREHEAT or START position (or
when the Cycle-Sentry control module initiates a unit start-
up with the Cycle-Sentry switch in the CYCLE position).
An open glow plug (burned out) can be detected with the
unit ammeter. The unit ammeter should show 28 to 30 amps
discharge while the Preheat-Start switch is held in the PRE-
HEAT position and the On-Off switch is in the OFF posi-
tion. A discharge of 28 to 30 amps means all four glow
plugs are working. If the discharge rate drops below 28
amps on PREHEAT, at least one glow plug is bad.
To isolate an open glow plug, remove the jumper bar and
test each glow plug individually with an ohmmeter or a
jumper wire and ammeter. Each glow plug should have a
resistance of approximately 1.8 ohms or a current draw of
about 6.9 amps.
A shorted glow plug will be indicated by the ammeter
showing full discharge when the Preheat-Start switch is
pressed, or when the current limiter between the ammeter
and the reset switch is burned out. Check each glow plug, a
shorted glow plug will have very low resistance.
THERMOGUARD µP-VI
MICROPROCESSOR CONTROLLER
Refer to the THERMOGUARD µP-VI Microprocessor
Controller Diagnosis Manual TK 50566 for complete ser-
vice information about the Microprocessor Controller and
the related components.
1. 1.8 Ohms
Testing Glow Plugs
sp2007
1
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