Hello group. I am having issues with my 13 Pathfinder and the AC. The compressor went out a couple weeks ago and had a new one installed. After install the compressor and radiator fans will not turn on. Even when pushing the ac button on the dash neither will power on. I ran the self test and bothe the clutch for the compressor and fans will power on. I have checked every fuse and everything is good. Any ideas of what to check next and/or has anyone delt with this problem before. I don't know of the pressures on my freon levels but plan to have another shop check those. Any help is appreciated

The ECM won't let the compressor turn on if the refrigerant pressure is too high or too low, so that's the first thing to check. If your scanner will stream the A/C pressure from the ECM, normal pressure with the compressor off will be about 1.0V, with the compressor running about 1.5V. I'm not sure on the exact cutoff voltages, but my guesstimation would be around 0.5V low and 2.3V high.

When I first hooked up the to live scan it showed both compressor and fan were on. Will that show up and the ecm still overide?

Also, when do the radiator fans normally kick on? It seems they would always run when I started the motor. That is what has me stumped. Are the compressor and fans linked together electrically and sequentially?

Linked electrically no, but in software, yes. The radiator fans will always kick on at low speed when the compressor is running. Some live scans show the compressor request and not the actual condition. There are four different devices involved and the first three can all veto a compressor request for various reasons. The HVAC can cancel it if the evap temp, cabin temp, or ambient temp are too cold. The BCM can veto it if the blower is stalled. Finally, the ECM can veto it if the pressure is out of bounds or the throttle position demands full power.

Thanks that makes alot of sense and helps me better understand. I am a mechanical type guy not much on electronics. I will get the pressures check on the freon and see what happens.

You have any pre advice if that is not the trick?

I am thinking possible the head unit or the amplifier control module behind the head unit or the sun sensor

Fred775 wrote: ↑

Wed Jul 10, 2024 11:15 am

Thanks that makes alot of sense and helps me better understand. I am a mechanical type guy not much on electronics. I will get the pressures check on the freon and see what happens.

You have any pre advice if that is not the trick?

I am thinking possible the head unit or the amplifier control module behind the head unit or the sun sensor

The head units very rarely fail. I think I've seen three in the last decade, and one of those was a flood victim. The sensors are the usual culprits. They're all NTC type sensors (resistance falls as temperature rises), which means they all read "Siberia" when they go open circuit. The HVAC won't run the compressor in Siberia.

The ambient is the one that shows temperature on your dash, so that's easy to check. The cabin sensor is in the lower dash near the driver's right knee, the evap (intake) sensor is inside the HVAC Unit but the connector is behind the glove box on the side of the HVAC. You can check both of them by disconnecting the sensor, then shorting the connector on the car-harness side with a small, cut-off safety pin. That changes "Siberia" into "Sahara", so if the compressor kicks on, you know the sensor is defective.

PS - There's a full set of factory service manuals for your ride in Nico:
https://www.nicoclub.com/nissan-service-manuals

You want the section for "Heater and Air Conditioning Control System".

Thanks! That is a great help. Only other question is...will there be any other time the radiator fans will kick on without the compressor running? I have been driving it around alittle bit here and there to see if the fans will kick on at some point but am yet to see or hear them running?

Great my next steps are:
Check freon levels
Start jumping sensors (test with engine running I assume)
Possibly change out the amplifier module, ben having issues with the direction of air flow. Saw in another thread that solved that problem.

I had the service manuals and have been reading through them but it's alot if your not a service tech.

Fred775 wrote: ↑

Wed Jul 10, 2024 12:37 pm

Thanks! That is a great help. Only other question is...will there be any other time the radiator fans will kick on without the compressor running? I have been driving it around alittle bit here and there to see if the fans will kick on at some point but am yet to see or hear them running?

Great my next steps are:
Check freon levels
Start jumping sensors (test with engine running I assume)
Possibly change out the amplifier module, ben having issues with the direction of air flow. Saw in another thread that solved that problem.

I had the service manuals and have been reading through them but it's alot if your not a service tech.

Airflow issues are more likely to be from the mode actuator than the control circuitry.

The radiator fans should kick on when the engine temperature gets high enough. Leave it idling for a long time and eventually you should hear the fans start running periodically. They'll rarely come on when driving unless it's uphill in 120 degree temperatures. There's plenty of forced air in most normal driving conditions.

Thanks. I will update once I get the freon levels checked out

Well got the pathfinder back today. Took it to another shop yesterday and the mechanic found leaks at both the intake and discharge side of the new compressor I just had put in by another mechanic. FYI...change the seals on the hoses if you take them off. That's all my problem was. Mechanic used the old seals and didn't check for leaks. He thought it was good to go but when it sat all day before I picked it up it all leaked out.

Only issue I have now is the mode switch for air flow direction doesn't seem to work well. New mechanic tried to see if he could re-calibrate it but there doesn't seem to be an option for the pathfinder.

Thanks again for all the help. Was dreading tearing apart the dash this weekend but now I can sit back and relax

Exactly what are the symptoms with the mode control? The defroster gets 29% or more flow in all foot positions, so you may be mistaking a design condition for a malfunction. See the chart on HAC-26 here for the percentages of flow on each setting:
https://www.nicoclub.com/service-manual ... %2FHAC.pdf

When you set it to head (mid position) it will blow at your feet. It always goes to defrost everytime you select defrost, defrost feet. But the mid position is what I have the most problem with. Never seems to be 100%, always stuck mid defrost or mid feet.

That sounds like the defrost door has leaky seals or isn't closing fully. Foot-and-face (second position on the chart) shouldn't be sending anything to the defrost duct. So we're on the same page, the positions on the chart from top to bottom are called Face, Foot-and-Face, Foot, Foot-Defrost, and Defrost. Note that the system is designed to run on Auto, a lot of them get goofy about temperature when you dial it manually. They don't usually get goofy about mode, but you could try putting it on Auto first and then selecting the position, that should clear any confusion in the peabrained computer.