Still Chasing AC Problem - Now Going After An Unexpected Noise

[thom4782]

If anyone has some insights, I'd greatly appreciate hearing them.

When the engine is running and I turn on the AC by pushing the snowflake button, there is a whine that come from front area of the the passenger foot well. I would guess that it is the AC/heater blower fan, but here's the strange thing. The pitch of the whine increases with engine speed and not fan speed.

Some I'm thinking it could be expansion valve noise. Does this make sense to anyone. It's different than the expansion value noise one hears then the refrigerant is low. It's definitely not a wheel bearing because it whines when the car isn't moving. The only way I can get it to start and stop is to push the snowflake button on and off.

So does anyone have a guess as to what else might be causing the whine. I can't think of anything up from that changes pitch with changes in engine speed.

Thanks

[Meir]

Originally Posted by thom4782

If anyone has some insights, I'd greatly appreciate hearing them.

When the engine is running and I turn on the AC by pushing the snowflake button, there is a whine that come from front area of the the passenger foot well. I would guess that it is the AC/heater blower fan, but here's the strange thing. The pitch of the whine increases with engine speed and not fan speed.

Some I'm thinking it could be expansion valve noise. Does this make sense to anyone. It's different than the expansion value noise one hears then the refrigerant is low. It's definitely not a wheel bearing because it whines when the car isn't moving. The only way I can get it to start and stop is to push the snowflake button on and off.

So does anyone have a guess as to what else might be causing the whine. I can't think of anything up from that changes pitch with changes in engine speed.

Thanks

Hi Thom.
It might sound stupid, but make sure the noise is not coming from the speakers.
If the stereo system has a bad ground (or another issue), activation of an accessory can lead to an alternator noise in the speakers.
I know it's a long shot, but just put your ear next to the speaker (dash and door) when you press the button.

[copsahl]

Have you tried listening for the whine up-front, near your passenger side ac condenser?

[thom4782]

Thanks for the suggestions so far.

The noise isn't radio related. It's there whether or not the radio is on.

I'll double whether it comes from one of the condensers. I might be surprised. The sound however seems like it coming from the area under the expansion value / pollen filter. I suppose it could be the evaporator.

Two follow-on questions if the sound is coming from the condenser or the evaporator, hyw would one of these components make a whining sound? Why would it change with engine speed? I could guess the answer to the second question -- the refrigerant pressure and flow rate increases as the compressor speed increases. If the noise is flow related, the its pitch could be higher with greater flow rates.

[Meir]

Thom. Try this.
If the evaporator is leaking, AC oil should be released along with the freon.
Put the AC on high, and activat the defroster (direct the air to the windshield )
After 5 minutes, use your finger and inspect he windshield for oily substance.
If it is not oily, at least you will know the evaporator is fine.
Did you charge the AC with a dye?

[thom4782]

Hi Meir:
The AC was charged late last summer with a dye. It showed a leaking expansion value. I replaced it as well as the receiver / dryer. Now, four months later, the AC isn't cooling so there must be another leak. I'll try the window trick to see if its the evaporator. Hopefully not.

I'm still wondering about the whining noise. It's been making before the system was recharged, when it was freshly recharged and now several months later with the refrigerant level low.

Thom

[newBgeek]

Hate to drudge up an old thread, but I'm also having this whining noise coming from the expansion valve. The A/C still works and blows cold air. Otherwise, same symptoms as the OP. Anyone else experience this and found a cause?

[smshirk]

I hear thst noise from time to time but not often and only fir a couple of seconds. Until I saw this thread I wasn't sure it was the AC but I'm pretty sure it is now.