AC Compressor is not getting power

Hate to resurrect an old thread as my last. But did you ever figure this out? Having the exact same problem, intake sensor seems to be functioning within a couple ohms of FSM value table at temp. compressor comes on for about a minute and a half when truck is cold. Then shuts off and won't turn back on. Pressures look fine (30 low, 150 high).
Replaced IPDM and front air control from known good parts and still same problem.
12v applied to compressor will turn it on just fine.
Compressor replaced already with known good unit
Refrigerant pressure sensor replaced with new OEM unit
Grounds all cleaned, checked for continuity
Replaced blower resistor as I found that also has a circuit that ties into the AC as well (red wire)

If you ever figured it out, could you reply and tell me what it is? It's almost 90 here in NC now too and ungodly humid.

RamTest said:

"Auto Active Test". This is a self test, you need NO scanners to complete it.
See 4 pages of service manual pdf below.

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Active self test when cold, the compressor clutch can be audibly heard engaging.

Having brother drive it for an hour while he's doing his stairway errands. And then will test it once he gets back and the AC is in its inoperable state.

Will report back. Maybe I just got a bad BCM...

RamTest said:

What was your result of the "Auto Active Test" ?

Click to expand...

Both when vehicle is cold and hot, the compressor clutch actuates audibly 5 times as it should.

So my assumption is I either got a bad used BCM. Or I have a CANBUS line issue.

Logic this out with me, if there was a short in the can H/L lines. Would there not be other things wrong with the truck? Those lines share junctions to both ecm and ipdm. So I would assume if there was a short. We'd have other problems with the vehicle aside from just AC not staying on.

Thoughts? New BCM is $500.

RamTest said:

I would pull and re-insert every fuse in the underhood and in-cabin fuse boxes. Be sure every fuse fits tight, and there is no corrosion or burns on the fuse blades. Any corrosion/burns requires the boxes be opened up to check the backside.
Also disconnect and reconnect every terminal on the ecm, relay, ipdm, and bcm.... basically every terminal you can find. Don't screw with them, just disconnect and reconnect.

When the compressor quits, does any other electric device in the truck also go out?
Also, are you absolutely certain the refrigerant pressure is normal at the time it quits?

Click to expand...

Have done that three times now. Pulled and inserted every single plug the truck has. No corrosion on any of the old parts and new pages.

Haven't seen a single burnt spot on anything. All fuses are good. Test good. And relays have been swapped an uncountable amount of times in case that was affecting the internal IPDM ac relay somehow.

Nope, when it stops working. Absolutely nothing else malfunctions. Ac pressures are perfect. Refrigerant pressure sensor has the correct values as well. 5v/ground/reference voltage between 0-5.

I've charged it three times over this whole thing. Both via high and low sides (properly).

What's getting me is that the self test actuated the clutch both when truck was cold and when it was hot. That circuit from the ipdm is working. But clueless as to why it keeps shutting off.

Does the pressure sensor have a PID I can look at in the ecm or CONSULT? And compare to the measured value. Put a brand new nissan part in it but that could be it.

Welp, bumping this for the people who have this issue in the future.

Y'all ain't gonna believe this, but nissan has AC clutch shut off's IN THE POWER STEERING PRESSURE TRANSDUCER. The AC system has a shut off condition that tells the engine to take power from the compressor clutch on low idle conditions. It has the same thing with multiple different sensors and engine inputs as well that all feed back to the ECM.

The correct order of operations for anyone needing to verify this stuff is:
Front air control knobs, use a 5v reference/ground to send an AC request on signal to the BCM. If the blower motor is working correctly and the intake air sensor (the little thermistor probe in the hvac box) are both testing correctly. Then check the pins at the BCM for reference signal with AC button on/off.

From here it sends a signal to the ECM via CAN data lines (pulsed frequency) for the AC request ON/OFF. The ECM receives the signal, and takes input from several different sensors and sources (APP, TPS, RPS, PSS, etc...) and determines whether or not it's "Safe" to turn the compressor clutch on.

If it determines that it's safe, and all the incoming signals are within acceptable ranges, it will send a signal to the IPDM via a SECOND set of CAN lines that will tell the IPDM to turn the AC request On/Off, this is the PID that you see in the IPDM for "AC Request". If it is on, the ECM is working, if it is off, start back tracking.

The IPDM will then energize the internal AC relay and send power to the compressor clutch until the ECM see's interference on ANY of it's incoming sensor inputs and shuts the AC Request off.

In my case, the wires leading into the connector (and the connector for that matter), had melted under the constant heat there at the front of the motor (plus the original AC fan was bad so it never cooled off that side of the radiator/motor either). The wires were shorting inside the connector and cause the PSS PID to constantly flash on/off in my scan tool.

The SECOND I unplugged the power steering sensor, AC came on and worked perfectly -.-

New pigtail from eBay, and new power steering pressure sensor, and it's working as designed. Leave it to Nissan to work their AC into being dependent on a 5v reference from the STEERING system.

Was about to give up and put a new $800 BCM in it......Thank god the depths of AllData finally reveled this documentation on the system after hours of searching.