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Discussion Starter · #1 ·
Hi everyone, my radiator fans are not coming on during normal operation. They run on low when I turn on the ac, and run at high speed if I disconnect the coolant temp sensor. I replaced that sensor but still same problem. Any suggestions?
 

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NF Mod/Nissan Master Tech
2006 Pathfinder LE, 2003 Frontier SVE
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Are you having overheating issues? If not, it's probably fine. I don't know what you consider "normal operation," but the fans are controlled by the ECM corresponding to the vehicle speed, engine coolant temperature, refrigerant pressure, and air conditioner ON signal. The control system has 4-step control [HIGH/MIDDLE/LOW/OFF]. The ECM controls cooling fan relays through CAN communication line. One needs a Nissan Consult II or later scantool to properly test the cooling fan system.
 

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Discussion Starter · #3 ·
It's not overheating but is running hotter and starts to have ''knocking'' when in traffic at low rpm's, so I let the car idle for about 20 min in the driveway and noticed that the fans never came on.
 

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the one on the passanger side is the A/C fan the one on the right is the coolant fan. The A/C fan will only come on when you turn that on. They both will come on high if the temp doesn't start to fall. You need to focas on the coolant one first, either the relay isn't working of the motor has choked.

You can jump the fan to a battery to test that first, if that works without any noise or resistance you need to swap the relay with a known good one. Otherwise all there is are the fuse and the temp sensor.
 

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Discussion Starter · #5 ·
The fans work ok, if I disconnet the temp sensor both run at high speed. where are the relays located? I guess I'll start there. Thanks for the help.
 

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And where can one obtain said Nissan Consult II. Does it run on a PC and/or MAC? How does it connect to the car? Via the OBD port? Thanks for some help.
 

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Radiator fans operation

You are a Nissan tech so perhaps you can answer this. The car is a 2006 Sentra 1.8S

Issue: large cooling fan, US Passenger's Side Fan, also listed by you as "left" side...(left side of what?) It's on the USA passenger side and will be referred to as PSF. The other fan, the one you list as "right side" is the Drivers Side Fan and seems to work in conjunction with the A/C compressor, and will be referred to as DSF

The DSF fan working in conjunction with the a/c seems to work property. It cycles on and off with the compressor clutch. THE CAR DOES NOT OVERHEAT. Turning off the a/c means NO fans are working but the temp needle doesn't move visibly. It actually drops just a teeny bit when you run anound on the road instead of idling standing still. It does not overheat whether any fans are working or not. I can put my OBD tester on this and and get digital coolant readings but I don't think the coolant temp varies by more than +- 12 deg. F

THE PSF fan never seems to go on. It has a new motor. It has 4 connections and one of them has 12vDC on it when the A/C fan. I suspect it 's a two speed motor but I have never seen it go on. As stated before, the car does not overheat. The temp gauge consistently sits at just below the halfway mark and stays there, A/C on or off, sitting running idle in 90+ degree weather, or running on the road, up and down mountain roads, nothing seems to move it except the engine getting to operating temp.

So what is the story with the big PSF fan? When is it supposed to go on? Under elevated temps? At What degrees? Is there a relay possibly defective? I looked in the fuse box under the hood and there's a label for "FAN2" but no relay in that socket, not at least according to the drawing on the cover. If there is a relay, could you please give me a part description and show the exact location? It could be something really simple, like the relay.

I would greatly appreciate some technical help here about how and when the larger fan cycles on and off and if you are a Nissan tech you'll know the truth in detail here. Thanks for your time, whoever responds.

PS: didn't realize this was a Maxima topic. I'm new here, please excuse me.
 

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US Passenger side, if you're sitting in the vehicle, facing forward, is on the right side. When referring to "right" and "left" on a vehicle is always referenced when sitting in the vehicle. So, if you're sitting in the vehicle, which fan (right or left) is not working?

The cooling fans are referred to as cooling fan 1 and cooling fan 2. As was noted already in the thread the best way to check the fans is with a bidirectional scan tool (Nissan calls theirs the Consult II.) It might be easiest to find a shop that has a bidirectional scan tool and have them try to turn on the fans with the tool. Without a scan tool you're going to have to put the vehicle in the right conditions where it will turn on the fan you want to check. That's a lot more work.

Since I don't work on this vehicle all the time I don't know which fan is which and it makes a big difference in troubleshooting. I did find a wiring diagram online. Can you give me the wire colors going into the fan that's not working and which wire color has the 12 volts on it and when? One fan, "Cooling Fan 1" should have two 12 volt feeds (red/yellow wire) even when the key is off. If you can identify which fan has two red/yellow wire 12 volt feeds then that is cooling fan 1 and we can try and troubleshoot from there.
 

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Let's get the fan identity straightened out. The fan that does not work correctly is the one on the right side as you sit in the car, the passengers side in US model. The left side fan seems to be working in conjunction with the a/c compressor, but as I have noted, the right side fan never comes on. So which fan is fan1 and which is fan2? The right side fan has 4 contacts to enable hi/lo operation. Is this right side fan 1 or 2 ?

The car does not overheat, a/c on or off, sitting idling in 90 degree whether, climbing mountain road. it looks like the temp hardly varies. I'll get my OBD on it and give you exact temp numbers asap, but I don't think we have a variance of more than +-12deg F.

I'm starting to think fan relay. these are in a little panel box at the front right inside the engine compartment, I think.
 

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The fact that it's on the passenger side doesn't help me when it comes to the wiring diagram and being able to trace the circuit. I need to know "Cooling Fan 1" or "Cooling Fan 2." The only way to determine that is for you to tell me the wire colors going into the fan or fans. Then I can match that up to the right one on the diagram and we can trace the circuit.

There are three different relays, controlled by the PCM, that operate the fans. Yes, they are in the power distribution module under the hood. It looks like they're labeled "Cooling Fan Relay 1, 2 & 3."
 

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I don't have the car here right now but I can tell you that the right side motor has 4 leads and apparently is a multi-speed motor. It's also physically bigger than the left side motor which has but two wires. Does that help isolate them?
 

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Turning the key on to power but not to start. Both cooling fans come on with no engine running. Changed the cooling temp sensor and still have the same problem. If I remove the two relays "low and high speed" from the power box both fans will shut off and car will start without blowing a fuse to the ECM up until the car gets hot, then it blows the fuse to the Ecm again and you have start all over again. Your thoughts please
 

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NF Mod/Nissan Master Tech
2006 Pathfinder LE, 2003 Frontier SVE
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ECM fail safe turns the radiator cooling fans "on" using the fan relays in the IPDM/ER. The fact that the fans turn "on" before you even attempt to start the engine would suggest there is an issue with the ECM, either the ECM, itself, or an input to the ECM. Have you checked for stored trouble codes in the ECM? If you check and there is no communication, I would be highly suspect of a faulty ECM. In that case, it might be worth sending the ECM to a company that repairs them, like Circuit Board Medics, who can check it and see if there is a problem with it...and repair it, if it does. If you have a code or codes, then follow the factory service manual diagnostics for those specific codes.
 
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