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05 Nissan Altima 2.5S Whining noise when accelerating but only when I have the heat turned on. Once I turn it off it doesn't do it. Any answers to why it's doing this?

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  • Is the noise in the sound system (radio)?
    – Moab
    Apr 25, 2018 at 18:58
  • No not coming from the radio cause I always turn it off to try and hear where it's coming from.
    – Cynthia
    Apr 27, 2018 at 15:06

2 Answers 2

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Just from your brief description, I'd have to say the blower motor for the HVAC system is going out. They tend to last a long time, but when they start to go out, the bushings which support them (which the shaft of the blower motor rides on) starts to wear and dry out. The first sign of it is when you accelerate, there's a specific whining noise. You could also hear it during braking. When it gets bad enough, you'll hear it all the time, then the motor will just seize up and quit working.

I don't know about your Altima, but newer vehicles have made it a lot easier to change these out. Looking at the one specific to your vehicle, if you were to purchase it with the housing and the fan wheel as a unit, it looks to be a pretty straight forward replacement item. If you bought just the motor, taking it apart from the housing and fan would be a little bit more difficult.

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Does the noise appear to be coming from the engine compartment?

It might be that your A/C compressor is engaged (yes it often operates with heat on). Or its belt is loose. Have you tried turn on the A/C and compare?

Is the sound from within the passenger compartment?
Is it from the radio maybe? (Turn it off / on and compare to see)

Does the speed setting of the heater's fan matter?

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  • It could be the AC compressor. It's an ICVDC and these tend to get louder when the heat load (i.e. cabin temperature) is high (they only start destroking themselves once the evaporator temperature is approaching the water's freezing point, unlike externally controlled ones). The OP may try opening all doors and windows and turning AC on on a warm day. That way the compressor will work at full stroke and she may rev to check for any noises related to compressor full stroke operation. For destroked, close all windows and doors and turn recirculation/MAX COOL on, rev and listen for any noises.
    – Al_
    Apr 26, 2018 at 10:37
  • Piston compressors discharge and draw the fluid in pulses, so some RPM-related groaning-whining noise from the dashboard (caused by the lines vibrating due to the pulses), especially with high discharge pressures (i.e. hot ambient temperatures), can be perfectly normal with the compressor in operation. To check if the actual compressor is working look for its clutch hub. If it's stationary it's off. If it's rotating with the pulley, the compressor is working. Do that when you hear that noise.
    – Al_
    Apr 26, 2018 at 10:40
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    I will have my mechanic read these comments cause I have no idea what your talking about. Lol and I'll let you guys know what we figured out. Thanks for all the possible scenarios.
    – Cynthia
    Apr 27, 2018 at 15:10

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