radiator cooling fan

[PAUL MM]

Hey guys Just noticed my radiator fan doesn't come on anymore. Every once in a while , while idling the temp gauge will start going up past normal. A small press on the gas and it goes back to normal
Any ideas on what I can check. Tried doing a search but couldn't find anything.
THanks
Paul M

 

[davidf]

Mine only cycles occasionally, but the temp gauge never creeps up so I assume it's normal.

 

[Old Guy]

Check the #4 fuse in the dash fuse box and the #31 fuse in the main relay box. Check the connections on the rad fan motor and the rad fan resistor to make sure that they have not come loose. After that, things get more complicated. If the fan is not cutting in on the low speed setting (which it should do first) the fan 'low' relay could have failed or the radiator fan resistor could have failed. The next lowest cost failure is the coolant temperature sensor which is separate from the dash sensor. The high cost failures are the rad fan motor and the cooling fan control unit.

If it is not the fuses or a loose connection, then I suggest that you download the .pdf version of the electrical portion of the service manual from the links in the Prime Wiki and follow the trouble shooting procedure. You don't want to be doing the diagnose by replacement when it comes to the rad fan or the control unit.

 

[PAUL MM]

Thank you very much

 

[Larry Bastanza]

The other thing to check is the "fan control" unit. It is behind the rear interior panel, about mid way across the interior. Best would be to swap it with a known good one, and see if the fan comes on. I have not had many fail over the years, but at least one.

HTH,
LarryB

 

[silver2002]

Just for the record, check coolant level too.

 

[PAUL MM]

Thanks Guys appreciate it! hopefully I can get to it this weekend.

Larry thank you for your help on cel codes. I ended up changing coils on #2 /3 cylinders and spark plug on #2 car is running great

I still want to bring it to you to have the small oil leak checked and brake shudder prob

 

[warrenw]

check to see if the fan turns by hand. I had a hood rubber bumper get knocked off and it fell between the fan blade and the radiator. this cause the fan fuse to blow.

 

[Kaz-kzukNA1]

The rad fan is controlled by the Fan Control Unit (FCU) with the input from the Rad Fan Control (RFC) sensor located on the thermostat cover.

There are 3 coolant temperature related sensors on our NSX.
The RFC, TW (for ECU) and Temp sender unit (for the gauge assy).

If you had any services inside the engine bay, check the round 2pin connector at the thermostat cover.
If you don’t know the exact location, it will be easier if you just remove the airbox cover.
If it’s disconnected or loose, rad fan will never operate and yet, you won’t get any warning lights until it’s too late.....

You can check the Rad fan motor itself by applying 12V directly at the big 2pin connector located on the rad fan shroud.
Very rare to fail though.

If you have access to the 1K ohm resistor, just insert it into the mating connector at the RFC sensor on the thermostat cover.
This will force the FCU into high temperature mode and triggers not only the rad fan into high speed mode but also it will activate the Eng Bay cooling fan (if your NSX has one).
Disarm the immobilizer/alarm as you would do for starting the engine, turn the IG key into P2 On position (lots of lights on the dash/gauge display), no need to start the engine and even with the cold engine, your Rad fan will operate in high speed mode.

This method will bypass your rad fan resistor as well as the rad fan low speed relay so even if both of them failed, you can still check the rad fan with rarely used rad fan high speed relay.


The FCU could fail due to soldering crack.
However, normally when it fails, your rad fan and both R & L A/C condenser fans start operating even with cold engine or a/c CCU switched Off as soon as you turn the IG key into P2.

If you had coolant replaced recently or lost fluid, make sure to bleed the air following the workshop manual sequence.


Kaz

 

[PAUL MM]

THank you very much!