1999 Nissan Quest Raidator Fan did not turn on low speed

Hi vicauto2,

Thank you for the donation.

Your problem seems to be Fuse J ( 7.5 or 10 A ) no power supply. It should be hot at all times. Power to it comes from the 140 A fusible link. It could be a fault in the fuse box internal connections.

Try attaching a remote wire to the the fuse and apply battery voltage to test if the slow speed works.

Check the # 44 Fuse. It also works the fans.

You bypased the 7.5A fuse and that is the cause of the wires burning up as there was a shorting somewhere.

I have some varied data and would like to confirm this.

Where is the location of the 7.5 A fuse that you are refering to?

After some research I managed to get the testing procedures for the cooling fan circuits.

COOLING FAN CONTROL TEST (QUEST)
1. Check Low Speed Fan Operation
Ensure coolant level is okay. Turn ignition off. Disconnect cooling fan relays No. 2 and 3. See Fig. 6 . Start engine. Set A/C temperature control lever to full cold position. Turn A/C switch and blower fan switch on. Run engine at idle for several minutes. Cooling fan should operate at low speed. If cooling fan does not operate, go to next step.

2. Check Power Supply (Low Speed)
Turn ignition off. Disconnect cooling fan relay No. 1. Turn ignition on. Measure voltage between cooling fan relay No. 1 harness connector terminals No. 1 (Blue wire) and ground, and terminal No. 5 (White/Blue wire) and ground. See Fig. 7 . If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 29 (10-amp) and fusible link (75- amp). If fuse and fusible link are okay, check open in circuit between fuse block and relay.

3. Check Ground Circuit (Low Speed)
Turn ignition off. Disconnect cooling fan motor harness connector. Using ohmmeter, check for continuity between fan motor harness connector terminal No. 2 and fan relay No. 1 harness connector terminal No. 3 (Blue/White wire). If continuity does not exist, repair open in Blue/White wire. If continuity exists, check for continuity between fan motor harness connector terminal No. 3 (Black wire) and ground. If continuity exists, go to next step. If continuity does not exist, repair open or short in Black wire.

4. Check Output Signal Circuit (Low Speed)
Disconnect ECM harness connector. Check for continuity between ECM harness connector terminal No. 38 and fan relay No. 1 connector terminal No. 2 (Blue/Orange wire). If continuity does not exist, check repair open in Blue/Orange wire. If continuity exists, go to next step.

5. Checking Cooling Fan Relay (Low Speed) Remove cooling fan relay No. 1. Apply 12 volts and ground to relay terminals No. 1 and 2. See Fig. 7 . Check for continuity between relay terminals No. 3 and 5. If continuity does not exist, replace relay. If continuity exists, go to next step.

6. Test Cooling Fan Motor (Low & High Speed)
Disconnect cooling fan motor harness connectors. Connect positive battery voltage to fan motor terminal No. 2 and ground to fan motor terminal No. 3. Fan motor should operate at low speed. Connect battery positive to fan motor terminal No. 1 and negative lead to fan motor terminal No. 3. Fan motor should operate at high speed. If fan motor does not operate as described, replace fan motor. If fan motor is okay, check ECM pin terminals and/or wiring harness connectors for corrosion and damage. Repair or replace as necessary.

Do the above test and see what you come up with.

You mentioned the fuse was ok but did not have power to it. It should not have shorted. For testing of circuits, it is best to test with intermittent touching the contacts to confirm if it is horting first and the point of contact should be at the power source and not the component side.

There are diagnostic equipment that can be plugged in test the various circuits but these are rather expensive items.

The ECM is located behind right side of dash. Removal of the ECM would facilitate testing and AC components need not be removed.

Removing the glove box should allow you to access the ECM. I do not have much info on the ECM removal except the view of the instrument panel.

Recheck the wire connections, look out for loose connectors. Check if any ground wire had been loosened and not retightened.

Removal of battery could cause the securrity system to be armed when reconnecting. Try closing all doors and using the key to lock and unlock the doors.

Lets try to see if you can get a manual reading of the MIL.

MIL reading data is for Quest and you need to check the ECM for the slots required to activate it.

Test the OBD-II terminal # 16 for battery voltage at all times. Nissan should be compatible with generic OBD-II scanners.

There is a possibility a power supply or ground is missing causing the problem.

Did you recheck all the fuses, especially those in Power Distribution Centre under hood?

Here is the PCM identification.

There are no recommended PCM testing except by substituting. Sensors and circuits can be tested but not the PCM.

Removing the ECM should not cause any problem with the sensors. I would suspect a loose connection somewhere.

The sensor on the bell housing is known as crank sensor but for quest it is located at crank pulley side.

When ECM is disconnected, faults would be erased and it would require some cranking ( 15 seconds) for the crank or cam sensors to register. Some codes needs the ignition to be turned off and on again to crank for them to register as they are require 2 trips to set the code.

Sorry I made a mistake when refering to the cranksensor location. It should be on the bell housing.