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Intermittent "moaning" from AC? by 87_special
Started on: 11-16-2021 03:20 AM
Replies: 7 (110 views)
Last post by: 87_special on 11-23-2021 06:25 PM
87_special
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Report this Post11-16-2021 03:20 AM Click Here to See the Profile for 87_specialClick Here to Email 87_specialSend a Private Message to 87_specialEdit/Delete MessageReply w/QuoteDirect Link to This Post
I've noticed a strange noise coming from my dash area. It's a moaning sound which is different from the usual vacuum blend door noises that these cars make when changing AC functions. The "moaning" is similar to a passing sport bike but deeper and can be felt in the pedals. The noise is also intermittent while driving and using the AC. Today it started while idling at a stop. I hit the off button and the sound disappeared. Strange issue, but maybe someone has experienced it.

I recently (month ago or so) replaced the dryer and orifice before a long vacuum and refill with 38 oz R134 and 4 oz of ester oil. The orifice is an extreme weather variable orifice (FOUR SEASONS 38904). The AC works wonderfully with 40* F temps on a 75*F day.
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Report this Post11-16-2021 10:58 AM Click Here to See the Profile for RWDPLZClick Here to visit RWDPLZ's HomePageSend a Private Message to RWDPLZEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 87_special:
refill with 38 oz R134 and 4 oz of ester oil.


The Fiero A/C system has a total capacity of 8 oz of oil, did you only add 4oz? No idea about the noise unless the blower motor bearing is starting to go out?
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Report this Post11-16-2021 04:32 PM Click Here to See the Profile for 87_specialClick Here to Email 87_specialSend a Private Message to 87_specialEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by RWDPLZ:


The Fiero A/C system has a total capacity of 8 oz of oil, did you only add 4oz? No idea about the noise unless the blower motor bearing is starting to go out?


Thank you for reply. I had the engine out (ac lines disconnected) and lost refrigerant and a little oil. After reinstall, I changed the orifice and did the normal vac and fill with a little oil added (2 oz maybe). I then realized my stupidity of neglecting the dryer and had a pinched o-ring on the orifice connection. This prompted me to redo the procedure but with a new dryer and new variable orifice tube. At this time I added 4 oz of Ester oil. System pressures are within spec. Should I add more oil?

Blower motor bearing sounds possible. The noise does sound similar to spinning fan blades scraping it's housing or a fender liner scrubbing a tire. I already checked the fender liners and they are good.

Thanks,
Joe

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Notorio
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Report this Post11-16-2021 05:57 PM Click Here to See the Profile for NotorioSend a Private Message to NotorioEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 87_special:
Blower motor bearing sounds possible. The noise does sound similar to spinning fan blades scraping it's housing or a fender liner scrubbing a tire. I already checked the fender liners and they are good ...


Joe, a lot of folks on here have opened up their blowers to discover happy little families of varmints moved in with all the comforts of home. You might want to check to see if it is just full of varmint materials and otherwise OK ...
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87_special
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Report this Post11-16-2021 06:51 PM Click Here to See the Profile for 87_specialClick Here to Email 87_specialSend a Private Message to 87_specialEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Notorio:


Joe, a lot of folks on here have opened up their blowers to discover happy little families of varmints moved in with all the comforts of home. You might want to check to see if it is just full of varmint materials and otherwise OK ...


That's a good point. I will check it when I inspect the blower. I haven't notice any strange or foul smells.
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87_special
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Report this Post11-20-2021 01:48 AM Click Here to See the Profile for 87_specialClick Here to Email 87_specialSend a Private Message to 87_specialEdit/Delete MessageReply w/QuoteDirect Link to This Post
Today I removed the blower motor to inspect for any rubbing. No signs of worn bearing or rubbing on the housing. The evaporator core looked decently clean also. No signs of critters either.

I'm thinking this strange noise might be fluid dynamics and pressure related. Maybe the variable orifice tube or some restriction in the system is causing it? Like when pinching a balloon and letting the air out slowly to make it squeal. Idk, just spit-balling.
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Report this Post11-21-2021 11:43 PM Click Here to See the Profile for NotorioSend a Private Message to NotorioEdit/Delete MessageReply w/QuoteDirect Link to This Post
Glad to see that you weren't invaded by varmints. Perhaps the moaning sound will become a unique feature of the car that will grow on you over time ...
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Report this Post11-23-2021 06:25 PM Click Here to See the Profile for 87_specialClick Here to Email 87_specialSend a Private Message to 87_specialEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Notorio:

Glad to see that you weren't invaded by varmints. Perhaps the moaning sound will become a unique feature of the car that will grow on you over time ...


It's rather unpredictable so I doubt I can just get used to it. haha

Another Fiero owner mentioned that it might be old, collapsing vacuum lines feeding the climate control system. I also could have a small leak which is causing the collapsed lines to "moan" as air is pulled into the line. Like I said earlier, the noise is similar to a balloon squealing when outlet is pinched and air is released. It's hard to believe that nobody has experienced this. I will investigate under the dash this weekend and report back.

I hope I solve this issue. Maybe this thread will help others in the future.

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