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.
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Some observations associated with this little exercise.
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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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</OGiven 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.
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Some observations associated with this little exercise.
- 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
- 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
- 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</O
