TM 5-2420-230-24-2
Air Intake Manifold Heater (010-072)
B3.9 and B5.9 Series Engines
Page 10-58
Section 10 - Air Intake System - Group 10
Troubleshooting for Heater System
Wait-to-Start (WTS) Lamp Not Functioning
Check wiring, socket, bulb, ground signal from controller, and
bulb power supply from the keyswitch. Correct any electrical
problems with the WTS lamp. WTS lamp will flash one time
a second if an open circuit is detected in the temperature
sensor.
Temperature Sensor Failed
Check resistance across the temperature sensor pins J1A
and J1B at room temperature and in an ice bath 0C [32F].
The resistance should be approximately 800 ohms at room
temperature and 2000 ohms for the ice bath. Check the re-
sistance to ground (-) for an open circuit.
NOTE: Make resistance checks with the keyswitch in the ON
position to make sure there are no ground (-) problems.
Replace defective sensor.
Relay or Contactor Failure
Check relays or contactors for an audible click during opera-
tion. Check for pitting or burning in the relay by measuring
resistance across the high-amperage terminals when relay is
closed. Replace relay(s) if the resistance is high or an au-
dible click is not heard when it is acutuated.
Insufficient Ground (-) Connections
Check pin J1B for ground to the controller. Check the ground
(-) strap to the grid heater for high resistance. Repair or re-
place wiring.
Controller Malfunctioning
Check pin J2A for 12-VDC signal; inspect the wiring harness
for shorting, chafing, or burning. The controller operates be-
tween 6.5 VDC and 16 VDC. Check the connectors for good
connections. Replace the controller, if necessary.
NOTE: The controller will abort postheat if it senses a volt-
age drop below 9.5 VDC during preheat or a 10-second de-
lay or more between WAIT-TO-START (WTS) lamp off and
cranking, or an open temperature circuit.
L-1182