I am praying someone can help. I don't want to get rid of my G.
I posted this in the wrong group earlier this week, not one response. Where's the love?

2007 G35 Sedan 5AT- 172k miles.

So as everyone else gets....Fans on all the time.
Replaced the FCM with Beck/Arney brand. Overheated. Got a TYC fan (FCM and fans), same.

I figured it was the FCM, but it's not I am now on my 3rd replacement.

So it comes down to this:
With the AC off, the fan comes on at 213.8°F and turns off at 204.8°F religiously.
Once I turn on the AC, the fans start up and die off. Basically pulsing about every 5 seconds.
This results in the engine climbing in temps. If I turn the AC off the pulsing continues even if the engine is above 213.8°.
Eventually its just enough to cool down when parked, but the fans cease to function properly.
I have to stop the car for a few and start it back it up.

I even tried to disconnect the battery for awhile. Nope!
I figured that the fans are drawing too much current and tripping the FCM, that's why my OEM FCM broke.
OEM fans drew 8-9 amps each. The TYC draw 7.9 and 9 amps.
I don't see a how a relay plays a role in this. The FCM has + and - and some control wire, but something being stuck until it is unenergized sounds like a bad relay.

Anyone have clue or input? Where does that one wire to the FCM go?

Thanks, until now the OEM FCM is in place, but the fans wont last forever.

 

I would take a look at the FSM and figure out the control circuit for the fans with the A/C on. Normal (no A/C) operation is controlled by a thermostatic switch activating the relay. With the A/C on it's bypassed and controlled based on A/C load and compressor duty cycle. But I'm not sure how exactly it's actuated on the G's. Your idea of it being a relay is quite plausible in my mind. Something in the A/C circuit could be a little out of whack, making the fans non-functional under normal, no A/C, conditions.

When you turn on your A/C what does the compressor do? Does it have to same weird pattern of operation as the fans?

 

Well crap my wipers stopped working today.
Fuses good, only 12v to one pin when car is on. wiper switch does nothing to other pin.

I am thinking my BCM is bad and the Radiator fans are related.

 

Random stuff failing like that with good fuses definitely could be the BCM.

 

Well I got the wipers working. came disconnected and so dam quiet couldn't hear the motor over the radiator fans.

anyway, I get random key fob issues where they wont work unless your rubbing your pocket against the door.

I am going to hit the pull a part. There is one G just like mine. Hopefully the BCMs match. They cost less than $30.
Still need to find locksmith to program it.

 

Please help me here. I read your problem and I am facing a somewhat similar kind of an issue. If you can read my problem here in more detail and provide some feedback, I would be so grateful to you.
My G35x (5AT, 140K) has been overheating almost every day during summer when idling or at low speeds. I tested this the other day as well. Here is the issue, in short:

• A/C ON : Fans come on immediately, tested on a day with ambient temperature ~60°F, couldn't get the temperature of the engine to go beyond 185°F (even after idling for 15 minutes).
• A/C OFF : Fans come on at 213.8°F and turn off when the temps go down to 204.8°F. This happens ONLY for one cycle. The fans then start pulsing every 5 seconds and the temperatures keep climbing. I turned it off at 220°F. On colder days (~50°F) however, the cycle is done religiously and idles fine.

I have changed the FCM, I checked the radiator and looks fine, changed the thermostat, burped the system, heater works fine, tested relays (they can't be bad since the fans are working anyway), no signs of blown head gasket either.

Were you able to fix this? Please help me here.

 

Pressure test the cooling system to verify it's actually holding pressure, however!

I still think the problem is the motors themselves, your fan control module sends a DUTY CYCLE SIGNAL to the fans not just steady DC current to two different windings like the older style with high/low function, if the fans work fine at 100% duty cycle but don't at lower duty cycle (fan pulsing) that is a classic symptom of motor failure.

 

So my fan isn’t working on the passenger on my 06 coupe but the driver side works, I’ve changed the whole fan shroud with one from TRQ or something. As a mechanic said my ole oem fans were bad because one isn’t turning on so I bought a new one and still not working but I overheat on hot days with city driving.

 

Could be a bad fan relay on your IPDM