Controller Power, Ground, And Atc Switch; Background; Power And Ground Circuit; Possible Failure Modes - New Holland T8010 Manual

Controller Power, Ground, And ATC Switch

NOTE: See Electrical Schematic sections 60 and 61.

Background

HVAC ground is a grounding bolt at the back of the HVAC box. Ground is additionally provided from the common
wires through CJ6R1 on wire 309- or to ring terminal C2.
Since so many controlled directed components interact, intermittent HVAC ground can make reliable
troubleshooting very difficult.
The "intermittent" nature of the problem is further complicated since the fault can appear to move from component
to component.
Early testing for a stable and consistent ground at the HVAC ground bolt and CJ6R1 to ring terminal C2can greatly
simplify troubleshooting.

Power and Ground Circuit

ATC Controller
Whenever accessory power is present, 12V is fed the controller from fuse 47 (30 amp) through CJR6R1 to CJ8-17.
The controller is grounded from CJ8-18 to HVAC ground.
ATC Switch
The controller feeds 5V CJ8-26 through CJ6R1-L to the switch at pin 4; grounding CJ8-26 with the switch provides
the automatic mode request to the controller.
The controller feeds 5V from CJ8-25 through CJ6R1-M to the switch at pin 6; grounding CJ8-26 with the switch
provides the Defog/Defrost mode request to the controller.
The switch is grounded from pin S to chassis at CJ6R1-S.

Possible Failure Modes

1. Fuse 47 or open condition in power or ground to controller.
2. ATC switch failure.
3. Open condition in power or ground to switch.

Controller Power Supply and Ground Test

Steps and Test Point
1. Keyswitch ON and ATC switch to "A." Measure the
voltage between CJ8-17 at the controller and
chassis ground. Is 12V present?
2. Check fuse no. 47 (30 amp). Is 12V present?
3. Measure resistance from pin 18 at the controller to
HVAC ground. Less than 1 ohm?
Section 50 - Climate Control - Chapter 1
YES - Go to Step 3.
NO - Go to next Step.
YES - Locate and repair open condition between fuse
36 and pin CJ8-17 at the controller.
NO - Locate and repair open condition from fuse 36 to
switched B+. Go to next Step.
YES - See ATC Controller Tests. in this Section. Test
the pins directly related to the faulty component at the
controller.
NO - Locate and repair open condition from pin 18 to
HVAC ground.
50-1-56
Corrective Actions