Strange fan sound when I turn on car.....

[AcuraNSX]

Hello everyone,

I have this strange fan sound that immediately comes on when I turn on my 1991 NSX automatic transmission car. It comes from the front bay, not the engine/transmission bay. I thought maybe the A/C was on so I checked that and it was off and temperature dial was set to maximum hot and heater fan was set to off inside the car. I just can't figure out what that fan noise coming from the front of the car is.... It does go away once the car warms up. just don't know if that is what is draining the car battery quickly or not. Thanks everyone!

 

[natcc99]

Perhaps it’s your ABS pump?

 

[Old Guy]

The aspirator fan which is mounted in the center counsel area (just behind that little grill in front of the shift lever on a standard transmission car). It runs all the time when the key is in the run position. Normally, no noise from the fan; but, as it accumulates dirt it develops a ticking / whirring which gets louder. Easy to confirm by putting your ear down close to that grill and listening for the noise with the engine off; but, the key in the run position. Its an annoying; but, not really loud noise.

The ABS problem is easy to diagnose by opening the hood and have somebody listen to the unit while you start up the car. Do a search on ABS noise to find a discussion of causes and possible solutions.

Is the climate control unit in your car original? If so, chances are that it is suffering from the dreaded capacitor failure malady and I believe one of the side effects is unexpected operation of the blower motor. Lots of posts discussing that. Should be easy to check to see if the blower is running.

It has not been widely reported; but, the rad fan control unit can suffer from failure. I can't remember the details; but, with the front hood open it should be easy to tell whether unplanned operation of the radiator fans is the source of the noise.

Kaz posted something a while back about a weird problem caused by a sneak circuit involving the engine bay cooling fan which exists on auto transmission cars. The sneak circuit resulted in unplanned fan operation (can't remember whether it was the rad fans or the interior blower fan).

 

[AcuraNSX]

Thanks Old Guy and Natcc99. It seems like the noise is coming from in front of the radiator or over front passenger wheel well. It definitely is not coming from ABS pump....this sounds like a blatant fan spinning. it isn't the radiator cooling fan as that cycles on and off like it is supposed to once the car has been idling for awhile. Just can't determine what or where the sound is from. Still confused....Has anyone else heard this noise immediately upon starting the car?

 

[Kaz-kzukNA1]

Hi, AcuraNSX.
May be I'm missing something here but if the issue starts when you turn On your car (not sure this means IG SW in P2 ON position before starting the engine or actually, you have to start the engine) and it keeps going on until the car warms up, can you not open the bonnet/hood to watch what's happening under there?

May be you have height/space restriction that you can't keep the bonnet opened???

The radiator fan is just in front of you so easy to check and if you place your hand inside the wheel arch just in front of the front tyre close to the floor, you can feel the air blowing if the a/c condenser fan is spinning.
That's where the air exits.

Do you have some sort of aftermarket oil cooler installed inside the front fender/wing?


There is a possibility that your Fan Control Unit (FCU) has soldering crack and triggering all sorts of fans around the car but again, you can see it.
You don't even need to start the engine if this was the case.

Although the sound may be coming from just the front, try opening the eng bay glass hatch and look at the eng bay cooling fan unit at the right side.
As your NSX is AT, you should still have it unless someone removed it.
If the FCU sufferes from soldering crack, not only the rad fan but also the eng bay cooling fan will start spinning even when the engine is cold and before starting the engine.

One example here;

1st unit has soldering crack issue and even when the engine was cold, you can hear the rad fan spinning in the background when IG SW turned into P2 On.
2nd unit is the good one and all you can hear is the faint hiss of the fuel pump for about 2sec.


Kaz

 

[crxguy52]

If it is indeed your fan control unit, I wrote a DIY on how to repair it. It's a pretty easy fix.

 

[jazzmann]

Hello everyone,

I have this strange fan sound that immediately comes on when I turn on my 1991 NSX automatic transmission car.

I hear a similar noise coming from behind the dash on my '91 manual exactly as [MENTION=7701]Oldguy[/MENTION] describes at the beginning of his reply. It starts as soon as I turn the key to position 1 (run, not start) and wait for the fuel pump to prime. It sounds like a fan, spins up slowly over a period of 1 or 2 seconds, and makes sort of a ticking a noise like a fan blade just barely catching something as it spins. It's very noticeable just sitting there, but goes away after the car warms up.

I'm thinking it's some kind of ventilation fan. I'm pretty sure every Honda/Acura I've had (at least those with automatic climate control) have some kind of cabin ventilation fan that moves air through the cabin even when the climate control is off. I'm going to have the CCU refurbished by BrianK sometime this year (however, this may be separate from the CCU), and will get this issue addressed at that time.

 

[Honcho]

I hear a similar noise coming from behind the dash on my '91 manual exactly as [MENTION=7701]Oldguy[/MENTION] describes at the beginning of his reply. It starts as soon as I turn the key to position 1 (run, not start) and wait for the fuel pump to prime. It sounds like a fan, spins up slowly over a period of 1 or 2 seconds, and makes sort of a ticking a noise like a fan blade just barely catching something as it spins. It's very noticeable just sitting there, but goes away after the car warms up.

I'm thinking it's some kind of ventilation fan. I'm pretty sure every Honda/Acura I've had (at least those with automatic climate control) have some kind of cabin ventilation fan that moves air through the cabin even when the climate control is off. I'm going to have the CCU refurbished by BrianK sometime this year (however, this may be separate from the CCU), and will get this issue addressed at that time.

Sounds like the CCU main fan, Will. Turn the CCU off and see if you still get the noise when you click to run. There is no other vent fan in the NSX, except for the aspirator fan, which is really more a sensor. I cleaned that thing when I first had the car, but didn't have the balls to pop off that retainer for a full disassembly.

 

[AcuraNSX]

Where is the Fan Control Unit located exactly?

If it is indeed your fan control unit, I wrote a DIY on how to repair it. It's a pretty easy fix.

Hello CRXGUY52. Where is the fan control unit located? You said behind passenger seat, but does that mean in engine bay behind the passenger seat or in literally behind the passenger seat in the car cabin? Thanks again! I have to check if the fan comes on immediately upon turning key to I or II or full ignition. Will post here once I find out....

 

[AcuraNSX]

Hi, AcuraNSX.
May be I'm missing something here but if the issue starts when you turn On your car (not sure this means IG SW in P2 ON position before starting the engine or actually, you have to start the engine) and it keeps going on until the car warms up, can you not open the bonnet/hood to watch what's happening under there?

May be you have height/space restriction that you can't keep the bonnet opened???

The radiator fan is just in front of you so easy to check and if you place your hand inside the wheel arch just in front of the front tyre close to the floor, you can feel the air blowing if the a/c condenser fan is spinning.
That's where the air exits.

Do you have some sort of aftermarket oil cooler installed inside the front fender/wing?


There is a possibility that your Fan Control Unit (FCU) has soldering crack and triggering all sorts of fans around the car but again, you can see it.
You don't even need to start the engine if this was the case.

Although the sound may be coming from just the front, try opening the eng bay glass hatch and look at the eng bay cooling fan unit at the right side.
As your NSX is AT, you should still have it unless someone removed it.
If the FCU sufferes from soldering crack, not only the rad fan but also the eng bay cooling fan will start spinning even when the engine is cold and before starting the engine.

One example here;

1st unit has soldering crack issue and even when the engine was cold, you can hear the rad fan spinning in the background when IG SW turned into P2 On.
2nd unit is the good one and all you can hear is the faint hiss of the fuel pump for about 2sec.


Kaz

Hello Kaz, Thank you very much for your response. It is not the radiator fan as I have popped the hood to investigate and it isn't the radiator fan because I can see that the fan blades are not spinning. It isn't the engine bay cooling fan because I have popped that and haven't noticed that spinning either. It sounds like some other fan. I shall check more intently and report back here

 

[Basal Skull]

It definitely is not coming from ABS pump....this sounds like a blatant fan spinning.

The ABS pump does sound like a fan that has one of the fan blades hitting something...
If you jump the relay on the abs pump in the relay box, you can run it to compare with the sound you are hearing.
http://www.nsxprime.com/forum/showt...ore-frequently-please-help?highlight=abs+pump
instructions for jumping the relay: http://www.danoland.com/nsxgarage/brakes/abs/abs.htm

 

[jazzmann]

Sounds like the CCU main fan, Will. Turn the CCU off and see if you still get the noise when you click to run. There is no other vent fan in the NSX, except for the aspirator fan, which is really more a sensor. I cleaned that thing when I first had the car, but didn't have the balls to pop off that retainer for a full disassembly.

this is with the CCU off. the only thing that's been done when I hear the noise is turning the key to the run position. This is the first I've heard about an aspirator fan so I assumed it was some kind of always-on ventilation fan that at least one of my other cars has had. Now we know, it's the aspirator fan. The CCU is having its own fan issues, but I can tell it's something entirely different.

 

[crxguy52]

Hello CRXGUY52. Where is the fan control unit located? You said behind passenger seat, but does that mean in engine bay behind the passenger seat or in literally behind the passenger seat in the car cabin? Thanks again! I have to check if the fan comes on immediately upon turning key to I or II or full ignition. Will post here once I find out....

It's on the firewall inside the cabin, behind the passenger seat. It's right next to the ECU and main relay. As others have said it'll cause the fans (and AC) to run when they're not supposed to, in my case it caused my AC to randomly not work.

 

[AcuraNSX]

Isolated the sound...at least I think

It's on the firewall inside the cabin, behind the passenger seat. It's right next to the ECU and main relay. As others have said it'll cause the fans (and AC) to run when they're not supposed to, in my case it caused my AC to randomly not work.

Hello again everyone,

It seems like the noise went away after disconnecting the battery for a couple days.....but then some sort of fan noise started up after several minutes. It seems like the noise is emanating from the front right bumper and I can feel a wind draft in the front right wheel well. Do you think it is the A/C condenser fan. Does the NSX have 2 condenser fans? One on each side, left and right, in front of radiator that you can see thru front bumper when you bend over and look into it? It seems like this one is firing on even though I didn't hit the A/C button inside the car. The left side one doesn't seem to come on randomly though.....any thoughts, crxguy52? Will your DIY write up help me fix this issue? Thank you again all of you!

 

[NSXGB]

NSX has 2 X AC fans on separate fuses (if I remember correctly). If they are running abnormally, it may mean you need to get your climate control board serviced due to leaky capacitors....

 

[Old Guy]

Yes its the condenser fan and yes two fans, one on each condenser. The fans are mounted behind the condenser so difficult (impossible?) to see with the front wheel liners in place. Both condenser fans on your 1991 are switched by the same relay so both fans should run at the same time. If the left fan motor is not starting up when the right motor is running, either the #36 10 A fuse for the motor is blown, the motor itself has failed or you have a broken wire.

The mystery operation of the right condenser fan is most likely caused by the fan control unit as described by crxguy52. Fractured or cold solder joints can lead to totally random operation. His repair process is the one to try (or buy a new fan control unit). The non operation of the left condenser fan is a separate problem.