Q70 5.6 Overheating when idling

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fabM45
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Joined: Mon Sep 07, 2015 4:41 pm
Car: 2003 M45

Q70 5.6 Overheating when idling

Postby fabM45 » Mon Jul 19, 2021 3:59 am

I just purchased a 2016 Q70L AWD 5.6L with 80k miles and it has an issue with overheating at idle. Also the AC doesn't blow cold until you start driving. The coolant overflow reservoir only had about a half inch of coolant but I filled it to in between the min and max lines with nissan blue coolant but the problem still persists. I believe my fans may not be turning on, or maybe just the AC condenser fan but haven't had a chance to check it. Does anyone have the part number for the OEM fan control module? All I see on infinityusa is the cooling fan 21481-1BH0B @ $883 and fan motor 21487-JF00B @ $424. I recall reading a post about just replacing the module which was much cheaper but cannot seem to find that post. Any info would be greatly appreciated


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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Q70 5.6 Overheating when idling

Postby VStar650CL » Mon Jul 19, 2021 6:22 am

On your ride each fan has its own 50A fusible link with its own embedded controller on each fan. Control is through the IPDM on request from the ECM via CAN (the ECM monitors engine temp and tells the IPDM what to do). The weak link in the system is that the relays are daisy-chained, so a blown relay fuse (fuse 42 in the IPDM) or a bad Fan Relay 1 will disable both fans. Here's your IPDM layout and the relay locations:

16 Q70L Components.png
16 Q70L IPDM.png

EdBwoy
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Re: Q70 5.6 Overheating when idling

Postby EdBwoy » Thu Jul 22, 2021 6:57 pm

The fan control module is part # 21493-4GA0A
I would do a little more troubleshooting before purchasing it though.

1. Open your hood and check the fans to see which one is running at idle, if at all
2. Turn your AC on to force both fans to run
3. Switch the control module between the left and right fan and repeat #2

Good luck, and please keep us updated.
https://youtu.be/uLGS3XnybWU

fabM45
Posts: 14
Joined: Mon Sep 07, 2015 4:41 pm
Car: 2003 M45

Re: Q70 5.6 Overheating when idling

Postby fabM45 » Sat Jul 24, 2021 6:48 pm

Well I can confirm that neither of the fans turn on at all even when the engine is hot and AC is on. Went ahead and tested radiator cap and thermostat, both are working well. Tested continuity of both 50A fusible links, both are good. Tested cooling fan 1 and 2 relays and both are good. Tested continuity of fuse 42 in the IPDM and its fine. I can confirm that each fan has its own control module, not just one like I had originally thought lol...So if everything is daisy chained, it seems odd to have both fans dead and not find a bad relay or fuse. I guess next step would be to check each fan individually with a multimeter before and after the control modules to see if they're getting power?

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Q70 5.6 Overheating when idling

Postby VStar650CL » Sun Jul 25, 2021 4:26 am

Those fans are a weird setup, they're brushed-DC but the controllers run them variable speed like a brushless. So the controllers are actually acting as SSR's (solid-state relays). The speed is controlled by a PWM signal from the IPDM on the Purple wire (pin 97 on the IPDM, it's common to both controllers). Your meter will see that as an analog voltage between 0V (fans off) and 5V (full speed). If you're not seeing voltage on Purple as the car gets warm, either the PWM driver in the IPDM is bad or you have shorted wiring. If you do have voltage, power the fans manually with a good ammeter (at least 20A) attached to see how much they draw. They'll peg your meter momentarily when they start up, but healthy ones should draw no more than 15A at a steady full speed. Identifix indicates it's not uncommon for them to draw too much current as they age and blow up the FETs in the controllers. It's also not uncommon for one controller to fail and go unnoticed until the second one fails, like people not noticing a headlight out until the second one goes.


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