EdgarG24

2012 G37 Sedan Base Model
98k Miles
Hello Forums,

I need some electrical inclined folks willing to suggest some ideas for me, my AC has been down for some months, and as the summer gets closer I would like to get it fixed.
Ac blows hot air, however AC button does not activate radiator fans nor ac compressor clutch.
Started with the basics. Went to an independent AC shop and they could not find any solution, they suggested an electrical issue and to check out a dealership...

Here's what I know.
checked freon pressure - pressure is sufficient.
Ran IPDM test - Magnetic Clutch actives, Low and High speed fans activate.

So I too concluded an electrical issue, so now im looking at AC Relay, AC pressure switch, Fan Module, Wiring Connections

My next step is to purchase a probe and start probing and checking everything out.

Questions:
Would I have to (professionally) remove freon prior to replacing pressure switch, then add back to the AC system?

Can I independently change AC relay, without replacing the entire IPDM?

Picture 1: Was taking a look and seems that there is a wiring harness unconnected, what exactly is this harness for?

Any suggestions are helpful, thanks.

Picture 1:

ILM-NC G37S

iTrader: (3)

I am mobile and away from my iPad but if you can peel back just a little bit of the harness to get the number & color of the wires that will help me identify the connector / purpose.

If it is the pressure sensor the system would have to be evacuated before replacement.

If it is the relay I believe the whole IPDM/er has to be replaced- not 100% certain as I'd have to check the FSM.

When I get back I'll fire up the iPad and check the FSM's.

EdgarG24

Hey thanks for the suggestions,
Im aware the other sensor attached is ambient temp sensor.
Here's a closer look,

EdgarG24

One more question, It seems that this pressure switch has some aftermarket modifications done to it or this OEM, (mind you im the second owner of the vehicle).
Can this have a significant effect in any way?

beefychicken

Referencing the last picture with the spliced in pig-tail. Those splices are incorrect for an area exposed to the elements and your problem may be corosion inside the splices messing up the signal from the pressure switch.

If this were mine, i would replace the splices with the type that shrinks and melts around the wire when heated and see if that fixes the issue.

EdgarG24

Hey thanks for the reply,
I had also questioned these modifications.

UPDATE:
Probed the switch with a multimeter, No Continuity whatsoever, tried all combinations...

Looks like the pressure switch might be shot as well...

Next steps to to replace those splices, evacuate system, replace switch, and re install freon (professionally) and go from there.


Thanks for the help, forums.

ILM-NC G37S

iTrader: (3)

I think it is safe to say that your issue lies in that mess.

First, the refrigerant pressure sensor (herein RPS) is NOT a switch, ie. not NO or NC so you won't read continuity across the terminals. It converts system pressure to a voltage and sends that voltage to the ECM to turn the compressor ON/OFF.

For whatever reason, the previous owner decided to bypass the OEM RPS connector (shown in your pic) and decided to not only "hardwire" the sensor in place but not even bother insulating the splices. My guess? Something happened that broke the male half of the connector (RPS-side) and rather than go through the chore of evacuating the system, removing the tank, replacing the sensor, reinstall/ recharge, they just decided to hardwire and "to hell with it."

Either way, I would "rework" that branch of the harness. Check to see if the original connector is still connected and intact. You can check for GROUND at pin 1 (VIOLET (purple wire)) and 5V+ at pin 3 (WHITE wire). Pin 2 (BLUE wire) is the reference signal that gets sent to the ECM (ranges 1-4V+ depending on refrigerant pressure).

Hope some of this helps.

EdgarG24

I appreciate all the insights and reconsiderations,

From my understanding most vehicles have a low and high ac pressure switch, so checking for continuity made sense, it seems that its not the same for the vq.

Yeah previous owner had a few "mickey mouse's" within the electronics I had to fix, it seems this might be the case as well. The original connector does not seem to be there, unless it's the one I was originally asking about in my very first thread. As far as "reworking" the wiring, would that mean in terms of just replacing that connector to the sensor and adding proper butt heated splices to the connections. Would there be any other ways to diagnose a bad pressure sensor, or is it not apart of the problem? As far as the AC Relay, would a continuity test would be effective? Would I have to go through the process of evacuate and refilling freon within the ac system?

I understand these question might be difficult to answer with out any prior context of my vehicle, but anything suggestions help.

Thanks.

ILM-NC G37S

iTrader: (3)

No, the traditional HI/ LO cutoff switches do not apply to most newer cars.

I would test the original connector (1st post) for power (5V+) and ground. If THAT connector tests good, then all you need is a new RPS. The connector would plug into the RPS.

Assuming that connector is GOOD, you can just remove the "Mickey Mouse" jerry-rigged nonsense and, hopefully, be good to go.

If that connector DOES NOT test good, then you will have to test those loose wires for power/ ground (ie. make sure they're good) before properly butt-splice that mess.

If it were me, I would go back to as close to a OEM state as possible.

Either way, the refrigerant will have to be evacuated prior to replacing the RPS. Once replaced, the system then has to be vacuumed and properly charged.

**NOTE** these cars get VERY cranky with refrigerant charges. The system calls for 1.21lb. of R-134a. There is very little tolerance +/- too much or too little will drastically affect system cooling performance.

beefychicken

@EdgarG24 I attached the connector diagram from the FSM.
The wire colors: Pin1 is Violet (V). Pin 2 is Blue (L). Pin 3 is Beige (BG).
The numbers are oriented by looking at the pin / face side of the connector with reference the lock mechanism.
Please verify that the hacked in pigtail is wired correctly, from your pictures it looks like pin 2 (L or Blue) is correct, but the other two cold be swapped.
Let me know if the pdf attachment doesnt work.

ILM-NC G37S

iTrader: (3)

While I rarely like to correct folks, I must in this case.

The orientation of the connector is when looking at it from the harness side of the connector. In other words, as the wire goes into the connector.

Notice on the diagram the icon "HS?" This indicates harness side whereas "TS" would indicate terminal (face) side.

Regardless, thanks to beefychicken for providing the diagram to OP.

EdgarG24

So does triangle within the diagram represent the tab used to pull the connector? Or is it the opposite?

ILM-NC G37S

iTrader: (3)

Irrelevant. The locking tab will vary. As long as you are looking at the connector from the wiring side and the tab is "up" that is how the circuits are laid out in the connector.

EdgarG24

Great, Makes sense.

Thanks again

beefychicken

Crap, i absolutely messed that up.
I just finished a halo mod on some tails and the tail light connector is also a harness. And that harness had to modded in order to get the halos to work with the brake / side-marker / tail / turn inputs. So when I was doing the pinouts using the FSM, I had to reference the the connector pins as a mirror image since it was the receptacle or component side, not the harness or car side that was being rewired.
Then when I responded to @EdgarG24 my mind was stilll stuck in mirror-mode and I made bad advice.
Thanks for the correction @ILM-NC G37S and @EdgarG24 i hope i didnt mess you up at all.