Test J: Insufficient, Erratic or No Heat

PINPOINT TEST J: INSUFFICIENT, ERRATIC OR NO HEAT

J1-J4:

J5-J8:

J8-J9:

Normal Operation

NOTE: DATC systems only.

Under normal operation, the automatic temperature control (ATC) solenoid and manifold receives a ground from the dual automatic temperature control (DATC) module through circuit 1070 (BN/LB). When the heater control valve vacuum solenoid is to be energized, the ATC solenoid and manifold receives power from the DATC module through circuit 1069 (OG/LB).

NOTE: Manual climate control systems only.

Under normal operation, the function selector switch receives engine vacuum. When OFF or MAX A/C is selected vacuum is applied to the recirculation vacuum control motor. When the temperature is in the full COOL position the Heater control valve vacuum switch applies vacuum to the heater control valve.

Possible Causes
- (DATC systems only) An open, short to voltage, ground in circuit 1069 (OG/LB).
- (DATC systems only) ATC solenoid and manifold.
- (DATC systems only) DATC module.
- (Manual climate control systems only) Function selector switch.
- Heater control valve.
- Heater control valve vacuum switch (if equipped).
- Stuck or bound linkage or door.
- Leaking or plugged vacuum hose.
- Temperature blend door actuator.