Engine Cooling Systems — Nissan Sentra B13 (1990-1994)

COOLING SYSTEM BLEEDING

Before filling cooling system, ensure heater valve is open to allow coolant flow through heater core. See OPENING HEATER VALVE table. When filling cooling system, ensure air relief plug is loose to allow trapped air to exit system. (Scheme 2)- (Scheme 12). Tighten air relief plug after filling cooling system.

Note. NX 1.6L and Sentra 1.6L use 2 air relief plugs. NX 2.0L and Sentra 2.0L use an air bleeder cap on heater hose pipe in addition to air relief plug.

Application		Procedure
Manual A/C		Move Temperature Control Lever To Full HOT Position. (1)
Automatic A/C
Maxima		Turn Ignition Off.
Pathfinder & Pickup		Turn Ignition On.
300ZX		(2)
(1) On 300ZX, turn ignition on also. (2) Turn ignition off then on. Simultaneously press AUTO and OFF buttons on A/C control panel and hold for at least 5 seconds. Release buttons. Press AUTO button once. Ensure 2 right segments on A/C control panel illuminate. (Scheme 1) If 2 right segments do not illuminate, press AUTO button as many times as necessary (this cycles through segment illumination).

(1)	On 300ZX, turn ignition on also.

(2)

Turn ignition off then on. Simultaneously press AUTO and OFF buttons on A/C control panel and hold for at least 5 seconds. Release buttons. Press AUTO button once. Ensure 2 right segments on A/C control panel illuminate. (Scheme 1) If 2 right segments do not illuminate, press AUTO button as many times as necessary (this cycles through segment illumination).

OPENING HEATER VALVE

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

TROUBLE SHOOTING & TESTING

Note. ECU refers to ECCS control unit. ECU controls cooling fan operation based on inputs from coolant temperature sensor and A/C switch.

Maxima (VE30DE)

On vehicles with A/C, go to next step. On vehicles without A/C, run engine at about 2000 RPM until engine is warm and radiator fans operate at low speed. If radiator fans do not operate at low speed, go to step 4). If radiator fans operate at low speed, go to step 3).
On vehicles with A/C, start engine. Set temperature lever to full COLD position. Turn on A/C switch and blower switch. Run engine with A/C on until radiator fan operates at low speed. If radiator fans do not operate at low speed, go to step 4). If radiator fans operate at low speed, go to next step.
On vehicles with A/C, turn off A/C switch and blower switch. On all vehicles, turn off ignition. Disconnect coolant temperature sensor connector. (Scheme 14)-16. Run engine until radiator fans operate at high speed. If radiator fans do not operate at high speed, go to step 7). If radiator fans operate at high speed, system is okay.
Turn off ignition. Disconnect radiator fan relay No. 1 connector. (Scheme 14)-16. Turn on ignition. Check power supply to radiator fan relay No. 1.
If power supply is okay, turn off ignition. Check continuity between radiator fan relay No. 1 and radiator fan motors, and between radiator fan motors and ground. If circuits are okay, check continuity of Light Green/Red wire between ECU connector terminal No. 19 and radiator fan relay No. 1. (Scheme 14)-16.
If Light Green/Red wire is okay, check radiator fan relay No. 1. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.
Check power supply to radiator fan relays No. 2 and 3. (Scheme 14)-16. If power supply is okay, check continuity of circuits between radiator fan relays No. 2 and 3 and radiator fan motors, and between radiator fan motors and ground.
If circuits are okay, check continuity of Light Green/Blue wire between ECU connector terminal No. 6 and radiator fan relay No. 1. (Scheme 14)-16.
If Light Green/Blue wire is okay, check radiator fan relays No. 2 and 3. See COMPONENT TESTING. If relays are okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.

Maxima (VG30E)

Run engine with A/C on until radiator fans operate at low speed. If radiator fans operate at low speed, go to step 4). If radiator fans do not operate at low speed, check power supply to radiator fan relay No. 1. (Scheme 17)-19. If power supply is okay, check radiator fan relay No. 1. See COMPONENT TESTING.
If relay is okay, check continuity of Light Green/Blue wire between ECU connector terminal No. 19 and radiator fan relay No. 1. (Scheme 17)-19.
If Light Green/Blue wire is okay, check circuits between radiator fan motors and ground. If circuits are okay, replace radiator fan motor(s).
Disconnect coolant temperature sensor connector. (Scheme 17)-19. Run engine until radiator fans operate at high speed. If radiator fans operate at high speed, system is okay.
If radiator fans do not operate at high speed, by-pass radiator fan relays No. 2 and 3 with a jumper wire. Check power supply to radiator fan motors. If power is supplied to radiator fan motors, check continuity between radiator fan motors and ground.
If circuits are okay, check continuity of Light Green/Red wire between ECU connector terminal No. 6 and radiator fan relays No. 2 and 3. (Scheme 17)-19.
If Light Green/Red wire is okay, check radiator fan relays No. 2 and 3. See COMPONENT TESTING. If relays are okay, replace radiator fan motors.

NX & Sentra (1.6L - Except USA Vehicles With A/T)

On vehicles without A/C, run engine at about 2000 RPM until engine is warm and radiator fans operate. On vehicles with A/C, start engine. Set temperature lever to full COLD position. Turn on A/C switch and blower switch. Run engine with A/C on until radiator fans operate.
On all vehicles, if radiator fans operate, system is okay. If radiator fans do not operate, turn off A/C switch and blower switch (vehicles with A/C). Leave ignition on with engine off. Check power supply to radiator fan relay No. 1. (Scheme 20)-22. If power supply is okay, turn ignition off.
Check continuity between radiator fan relay No. 1 and radiator fan motors, and between radiator fan motors and ground. If circuits are okay, check continuity of Blue wire between ECU connector terminal No. 9 and radiator fan relay No. 1. (Scheme 20)-22.
If Blue wire is okay, check radiator fan relay No. 1. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.

NX & Sentra (1.6L - USA Vehicles With A/T)

On vehicles without A/C, run engine at about 2000 RPM until engine is warm and radiator fans operate at low speed. On vehicles with A/C, start engine. Set temperature lever to full COLD position. Turn on A/C switch and blower switch. Run engine with A/C on until radiator fans operate at low speed.
On all vehicles, if radiator fans do not operate at low speed, go to step 6). If radiator fans operate at low speed, turn off A/C switch and blower switch (vehicles with A/C). On all vehicles, turn off ignition. Disconnect electrical connector from radiator fan relay No. 1. (Scheme 20)-22.
Operate engine until coolant temperature is at least 221°F (105°C). If radiator fans operate at high speed, system is okay. If radiator fans do not operate at high speed, check for power supply to radiator fan relay No. 2.
If power supply is okay, check continuity between radiator fan relay No. 2 and radiator fan motors, and between radiator fan relay No. 2 and ground. If circuits are okay, check continuity between radiator fan relay No. 2 and thermoswitch, and between thermoswitch and ground.
If circuits are okay, check radiator fan relay No. 2. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.
Check power supply to radiator fan relay No. 1. (Scheme 20)-22. If power supply is okay, check continuity between radiator fan relay No. 1 and radiator fan motors, and between radiator fan motors and ground.
If circuits are okay, check continuity of Blue wire between ECU connector terminal No. 9 and radiator fan relay No. 1. (Scheme 20)-22. If circuit is okay, check radiator fan relay No. 1. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.

NX & Sentra (2.0L With A/T)

Disconnect electrical connectors from radiator fan relays No. 2 and 3. (Scheme 23)-25. Start engine. Set temperature lever in full COLD position. Turn on A/C switch and blower switch. Operate engine at idle for a few minutes. If radiator fans do not operate at low speed, go to step 4).
If radiator fans operate at low speed, turn ignition off. Reconnect radiator fan relays No. 2 and 3. Disconnect radiator fan relay No. 1. Turn A/C switch and blower switch off. Disconnect electrical connector from coolant temperature sensor, located near oil filter. Operate engine until radiator fans operate at high speed.
If radiator fans operate at high speed, system is okay. If radiator fans do not operate at high speed, go to step 7).
Check power supply to radiator fan relay No. 1. If power supply is okay, turn off ignition. Check continuity between radiator fan motors and radiator fan relays No. 2 and 3, and between radiator fan motors and ground.
If circuits are okay, check continuity of Blue wire between ECU connector terminal No. 9 and radiator fan relay No. 1. (Scheme 23)-25.
If circuit is okay, check radiator fan relay No. 1. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.
Check power supply to radiator fan relays No. 2 and 3. If power supply is okay, check continuity between radiator fan relays No. 2 and 3 and radiator fan motors, and between radiator fan relays and ground.
If circuits are okay, check continuity of Blue/Black wire between ECU connector terminal No. 10 and radiator fan relays No. 2 and 3. (Scheme 23)-25.
If circuits are okay, check radiator fan relays No. 2 and 3. See COMPONENT TESTING. If relays are okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.

NX & Sentra (2.0L With M/T)

Start engine. Set temperature lever in full COLD position. Turn on A/C switch and blower switch. Operate engine at idle until radiator fans operate. If radiator fans operate, system is okay. If radiator fans do not operate, turn off A/C switch and blower switch.
Check power supply to radiator fan relay No. 1. (Scheme 23)-25. If power supply is okay, check continuity between radiator fan relay No. 1 and radiator fan motors, and between radiator fan motors and ground.
If circuits are okay, check continuity of Blue wire between ECU connector terminal No. 9 and radiator fan relay No. 1. (Scheme 23)-25.
If circuit is okay, check radiator fan relay No. 1. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.

Stanza

On vehicles with A/C, go to next step. On vehicles without A/C, run engine at about 2000 RPM until engine is warm and radiator fans operate at low speed. If radiator fans do not operate at low speed, go to step 4). If radiator fans operate at low speed, go to step 3).
Start engine. Set temperature lever to full COLD position. Turn on A/C switch and blower switch. Run engine until radiator fans operate at low speed. If radiator fans operate at low speed, go to next step. If radiator fans do not operate at low speed, go to step 4).
On vehicles with A/C, turn off A/C switch and blower switch. On all vehicles, turn off ignition. Disconnect coolant temperature sensor connector. (Scheme 26)-28. Run engine until radiator fans operate at high speed. If radiator fans do not operate at high speed, go to step 7). If radiator fans operate at high speed, system is okay.
Turn off ignition. Disconnect electrical connectors from radiator fan relays No. 1 and 2. (Scheme 26)-28. Turn ignition on. Check power supply to radiator fan relays No. 1 and 2.
If power supply is okay, check continuity between radiator fan motors and radiator fan relays No. 1 and 2, and between radiator fan motors and ground. If circuits are okay, check continuity of Light Green/Blue wire between ECU connector terminal No. 9 and radiator fan relays No. 1 and 2. (Scheme 26)-28.
If Light Green/Blue wire is okay, check radiator fan relays No. 1 and 2. See COMPONENT TESTING. If relays are okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.
Check power supply to radiator fan relay No. 3. If power supply is okay, check continuity between radiator fan relay No. 3 and radiator fan motors, and between radiator fan motors and ground.
If circuits are okay, check continuity of Light Green/White wire between ECU connector terminal No. 10 and radiator fan relay No. 3. (Scheme 26)-28.
If Light Green/White wire is okay, check radiator fan relay No. 3. See COMPONENT TESTING. If relay is okay, check radiator fan motors. If radiator fan motors are okay, check ECU connector.

240SX

Start engine. Set temperature lever to full COLD position. Turn on A/C switch and blower switch. Run engine until condenser fan operates. If condenser fan operates, system is okay.
If condenser fan does not operate, check power supply to condenser fan relay. (Scheme 29)and (Scheme 30). If power supply is okay, check continuity between condenser fan relay and condenser fan motor, and between condenser fan motor and ground.
If circuits are okay, check continuity of Orange/Blue wire between ECU connector terminal No. 9 and condenser fan relay. (Scheme 29)and (Scheme 30).
If circuit is okay, check condenser fan relay. See COMPONENT TESTING. If relay is okay, check condenser fan motor. If condenser fan motor is okay, check ECU connector.

300ZX

Check power supply to radiator fan relay. (Scheme 31)and (Scheme 32). If power supply to radiator fan relay is okay, check power supply to radiator fan motor. If power supply to radiator fan motor is not okay, go to step 3).
If power supply to radiator fan motor is okay, check continuity between radiator fan motor and ground. If circuit is okay, check radiator fan motor. See COMPONENT TESTING.
Check continuity between radiator fan relay and radiator fan motor. If circuit is okay, check continuity between ECU connector terminal No. 19 and radiator fan relay. (Scheme 31)and (Scheme 32). If circuit is okay, check radiator fan relay. See COMPONENT TESTING.

CONDENSER & RADIATOR FAN MOTORS

Disconnect fan motor connector. Apply battery voltage across fan motor connector terminals. Replace motor if it does not operate.

CONDENSER & RADIATOR FAN RELAYS

Identify relay type by color. (Scheme 13) Check continuity between relay terminals No. 3 and 5. On Brown relay, also check continuity between terminals No. 6 and 7. If continuity is present, replace relay. If continuity is not present, go to next step.
Apply battery voltage across terminals No. 1 and 2. Check continuity between terminals No. 3 and 5. On Brown relay, also check continuity between terminals No. 6 and 7. If continuity is not present, replace relay. If continuity is present, relay is okay.