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Aspirator fan fix

Joined
3 November 2011
Messages
3,419
Location
Saskatchewan, Canada
A number of members have posted information on NSX Prime about aspirator fan noise. This was of great assistance to me in diagnosing the annoying clicking noise that had been present since I acquired my NSX. I thought I would share some observations about the aspirator fan fix which may be of some value to other members facing this problem.
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Some of the posts suggested the fan noise results from dirt build up on the fan with a resulting loss of clearance between the fan blade and the fan housing which caused the fan blade to contact the housing. Having gone through the process of cleaning the fan, I think that these posts are partially correct. The noise is a result of crud build up, but does not result from the fan blade contacting the housing. After removing the fan assembly from the counsel; but, before pulling the fan apart, I spun the fan blade by hand and there was no noise. After separating the motor and fan blade assembly from the inlet part of the fan housing, I did find a bunch of stuff, specifically what looked like a hair ball wrapped around the center shaft of the fan. I have provided a couple of photos showing the fan assembly with the hair ball intact and the hair ball following removal (apologies for the quality of the latter photo as I don’t have a proper macro lens).
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Given the physical dimensions of the aspirator fan motor, I am guessing that it is a disc style brushless motor (I didn’t pull it apart so I can’t be sure). When you pull the fan apart, you will find that the fan, shaft and attached motor rotor assembly has a fair amount or radial and axial play once the bearing on the air inlet side is removed. It is possible that crud is building up and unbalancing the fan which could cause the fan blade to contact the housing once it is rotating fast enough; however, I didn’t spot any scrape marks from contacts on the inside of the housing so I don’t think that radial off balance is the problem. The shaft on the air inlet side of the fan appears to be a needle end style bearing (attached photo shows bearing in fan housing). When the fan comes up to speed the operation of the fan would suck the fan and its shaft forward on to the needle bearing and with the axial float built in to the motor, the whole assembly would spin on the needle bearing a bit like a top. I am guessing that the crud on the fan shaft unbalances the forces between the fan pulling the shaft on to the bearing and the magnetic forces on the motor rotor with the result that the clicking we hear is the fan shaft bouncing back and forth on the needle bearing. I removed the hair ball and used a Q tip and some electrical contact cleaner to clean off the fan blade (you need the contact cleaner because the clearance between some of the blades is too tight for the Q tip). I reassembled the fan and it now operates without any noise even though it still has axial play in the shaft at rest.

</O:p
Some observations associated with this little exercise.

  1. The needle bearing on the inlet end of the fan assembly has a set screw and nut on its back side which allows you to adjust the axial clearance on the fan / motor rotor shaft. Some members have suggested adjusting the shaft bearing to reduce the amount of radial clearance. You could adjust this bearing to remove all the radial clearance which eliminates the ability of the fan assembly to move up and down on the needle bearing, eliminating any possibility of the clicking noise. However, you are likely altering the design operating height of the rotor disc in the motor which may have some negative consequences. My suggestion is clean the fan assembly, reassemble and test. If you still have the noise, only then consider adjusting the clearance using adjustment on the needle bearing.<O:p
  2. Some members have suggested applying a vacuum cleaner to the inlet grill on the counsel to suck the dirt out of the fan or using a can of compressed gas to blow the crud out. Based on the condition of my fan, I don’t expect that this would have had any chance of removing the hairball. However, this might be a possible regular maintenance trick to prevent reoccurrence once you get it clean. I would be inclined to use the compressed gas rather than a vacuum cleaner. I expect that jamming the hose from a 15 amp shop vac on the inlet of the aspirator fan could get it spinning way beyond it design limit with the result that you may be taking the counsel and fan apart again to adjust the needle bearing to remove some new-found axial clearance in the fan assembly.</O:p
  3. The fan blade and inside of the fan housing on my fan appeared to have an oily residue on them which likely contributed to the accumulation of crud. My guess is that this is probably some vinyl cleaner / protectant that some previous owner may have got a little enthusiastic with during the application process. An obvious point would be to not spray this stuff around when the fan is running and be careful with spraying it in the vicinity of the fan opening even when the fan is not running. As a matter of choice I avoid the use of this stuff as it seems to contribute to the accumulation of dirt in the interior.<O:p</O:p
 
I have fixed several of these and after cleaning an adjustment is normally always required and something I recommend. Adjusting does not change the motor clearance, that side of the rotor is on a fixed bearing. Oily residual is normally some one spraying oil/wd40 to try and fix the problem.
 
I know there is more than one way to do this. I don't like removing my center console just to clean this fan. So what I do is when I see it dirty or lint build up I use a 20 gauge stranded wire and strip off the insulation. Bend the copper wires so it can fit threw the fins of the console and use them as claws and pick/pull out the crud/lint and such till I can see the fan blades. Works for me.
 
I agree with HUGH

I just unplugged mine problem solved does nothing anyway.
 
I know there is more than one way to do this. I don't like removing my center console just to clean this fan. So what I do is when I see it dirty or lint build up I use a 20 gauge stranded wire and strip off the insulation. Bend the copper wires so it can fit threw the fins of the console and use them as claws and pick/pull out the crud/lint and such till I can see the fan blades. Works for me.

I guess you can dig around and pull out the gunk but be carefull to not damage the sensor.
 
If the NSX were a human, the aspirator fan would be its tonsil. Get rid of the damn thing!

Its useful if you use climate control. Otherwise, I suppose its useless.

OP,
I've disassembled, cleaned, and oil'd my fan before and although the noise was significantly decreased, I can still hear it. I'm not sure if I'm too critical of the noise but its noticeable to me....maybe I just need to replace mine. I'm not sure if Brian's rebuilds go into the brushless motor but I did everything except breaking into that and the noise still persists with mine.
 
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I'm in South Florida, I drive my car 100 miles a day and use the A/C all the time. Trust me, you can toss the useless fan.
 
Thanks for the detailed analysis. Question: why did you go with electrical contact cleaner instead of, say, alcohol or detergent?

He used the electrical contact cleaner because it cleans really well since it's being blasted out of an aerosol can and it leaves no residue.
 
I guess you could toss the thermostat in your house since you use ac all the time there too. :tongue:

I realize that the thermistor in the fan unit functions as a thermostat but the system seems to operate normally without it. Looking at the graph on page 22-61 of the service manual you'd think that without the thing connected the car would "think" the interior temperature was very cold since the higher the resistance the colder the system perceives the car to be.

Do you think that with the thing disconnected the system defaults to a particular temp allowing the climate control to function in Full Auto mode?
 
the resistor is only used in auto mode, if your using it like 99% of the rest of us
a/c on and fan speed max then its not being used its bypassed, so its just spinning collecting dust till it starts to make noise.

its the exact fan/resistor thats in an Acura legend. 1990-1995

but if for some reason you want to use AUTO mode then get it fixed.

when you get into my BLK/BLK a/c ON and fan speed MAX and it still take 15 minutes to cool the car down.

the color black just soaks up the sun like a fat kid on cake.
 
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After cleaning mine, I put a piece of cooker hood filter just in front of the sensor between the unit and the dash board.

I hope this will prevent some dust to go to the fan :biggrin:
 
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I realize that the thermistor in the fan unit functions as a thermostat but the system seems to operate normally without it. Looking at the graph on page 22-61 of the service manual you'd think that without the thing connected the car would "think" the interior temperature was very cold since the higher the resistance the colder the system perceives the car to be.

Do you think that with the thing disconnected the system defaults to a particular temp allowing the climate control to function in Full Auto mode?

With the sensor disconnected it causes a fault and it just ignores the input all together. I guess with the other sensors it comes up with a guess on what it needs to do.
 
He used the electrical contact cleaner because it cleans really well since it's being blasted out of an aerosol can and it leaves no residue.

Many types of electrical contact cleaner (Deoxit for example) do leave a residue, hence the question. Maybe Old Guy can answer for himself.
 
Many types of electrical contact cleaner (Deoxit for example) do leave a residue.

Just like many types of cars suck such as German ones. If you go the aerosol route simply use something that leaves no residue. That's the correct type to use regardless of the one used by the OP.
 
Its useful if you use climate control. Otherwise, I suppose its useless.

OP,
I've disassembled, cleaned, and oil'd my fan before and although the noise was significantly decreased, I can still hear it. I'm not sure if I'm too critical of the noise but its noticeable to me....maybe I just need to replace mine. I'm not sure if Brian's rebuilds go into the brushless motor but I did everything except breaking into that and the noise still persists with mine.

I think the SECRET on these fans is to do what BrianK said, take it out, clean it and I go one step furthur.

Loosen the jam nut on the end, plug the fan into the electricial connector, turn on the key and then adjust the set screw (with the motor running) until the motor is smooth and quiet.

Give it a try.
Brad
 
In response to Russ, I used contact cleaner primarily because it was within handy reach on my work bench! That said, the plastic straw combined with the propellant in the can works well between the blades (which have a very tight spacing) and in the space between the back of the fan and the motor assembly. I used MG contact cleaner which claims to leave no residue and most importantly, claims to be plastic safe. Contact cleaners are very volatile which also means I also don't have to worry about drying the parts. Alcohol and alcohol based cleaners, being a polar molecule, are not so effective at breaking up oily residues.

I appreciate the comments about not wanting to pull apart the console. I had it apart because I was yanking out an ineffective IPod interface (replaced it with a Grom USB drive mounted in the trunk). For those advocating ditching the fan assembly completely, consider just clipping the motor leads (Bn/Y & Bk I seem to recall) on the fan connector. This leaves the RTD in the sensor circuit which may leave you with a partially effective auto mode (or 100% effective if you are of the opinion that the fan wasn't doing anything useful).

As a note, the repair remains effective with absolutely no fan noise - or I buggered up the fan / motor assembly and it is no longer turning, in which case my fan noise fix should last forever!
 
I think the SECRET on these fans is to do what BrianK said, take it out, clean it and I go one step furthur.

Loosen the jam nut on the end, plug the fan into the electricial connector, turn on the key and then adjust the set screw (with the motor running) until the motor is smooth and quiet.

Give it a try.
Brad



Adjusting set screw was the secret for me. I had cleaned it, put it back and it still made noise.
So I took it apart again, took off jam nuts to remove sensor, plugged it in and adjusted set screw while fan was turning. Then re-attached to console., seems to be good. I also added a tiny bit of filter material.

Great thread -
 
I recently cleaned mine and there was 19yrs of dust and cr@p stuck in the fan. LOL.
 
hi guy i just clean mine but still making noise so i just pin out the fan wire it easy to do (do not disconnect the plug) so the sensor still working with no noise:biggrin:
 
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