AC - hissing sound inside the car Topic is solved

[Clemens]

I've had 850ies so long that I can't remember if they all do it and my backup T5M has no AC:

After refilling the AC today I can hear a hissing sound from underneath the dash after shutting off the motor. It is AC related because it wasn't there before the refill. But that noise is not new, I've known it for years. Is that normal or does it indicate a hole in the system. I know my compressor has a very slow leak, but I couldn't hear that inside the vehicle.

[P80GLT]

Low gas level can cause this noise

[MoVolvos]

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Plus 1 on low refrigerant. Pretty rusty on HVAC theory but could be part liquid and gas rather than just liquid going through the expansion valve / metering device. Best to check pressure with gauges when adding refrigerant.
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[scot850]

Your evaporator has failed. If you have a small mirror, pull the lower dash on the passenger side and remove the 'resistor pack', and look in to the left. Look for dampness at the bottom of it. If it is the original you will likely find it has holed with condensation over the years. If you don't have the cabin filter mod added or the drain has blocked this will accelerated the failure. These started failing on 850's from 10 years old or so.

Neil.

[misha]

I don't know...i own my 850 for 24 years and it's ac system(ECC)always does that after turning the engine off...for a few seconds.

Last year i replaced drier,evaporator and heater core while i was in that area...and it acts the same.

For me...it's normal behavior.

[Clemens]

Your evaporator has failed. If you have a small mirror, pull the lower dash on the passenger side and remove the 'resistor pack', and look in to the left. Look for dampness at the bottom of it. If it is the original you will likely find it has holed with condensation over the years. If you don't have the cabin filter mod added or the drain has blocked this will accelerated the failure. These started failing on 850's from 10 years old or so.

Neil.

It's been doing it for years. and the dye in the R134 leaves no traces under the dash, only in front of the compressor. Misha's experience aligns my feeling that it's always been there.

[Clemens]

no, I just had it refilled today by my indie.

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Plus 1 on low refrigerant. Pretty rusty on HVAC theory but could be part liquid and gas rather than just liquid going through the expansion valve / metering device. Best to check pressure with gauges when adding refrigerant.
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[MoVolvos]

no, I just had it refilled today by my indie.

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Plus 1 on low refrigerant. Pretty rusty on HVAC theory but could be part liquid and gas rather than just liquid going through the expansion valve / metering device. Best to check pressure with gauges when adding refrigerant.
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Refill means there was a leak, was it resolved? I can't remember ever having to recharge an AC system so I'm very thankful.

Some cars are louder than others but I didn't hear anything from the 02 V70 XC when I used it today. Not to second guess your indie but some mechanics are excellent at R&R but AC and alignment are 2 areas that can be difficult to troubleshoot if you don't fully grasp the theory and concepts. Your AC can still work on low refrigerant but I guess you have to wait and see.
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In many of his videos he said that AC is not for the faint hearted and even otherwise good mechanics have difficulties. He messed this one up and had to take it to his friend's shop.

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At the end this video he said the even the professional technician have trouble with the AC.

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[scot850]

Ok, have you ever replaced the Schraeder valve by the dryer on the low pressure line. The o-ring in that can fail.

However if you say that it has been like that for years, and otherwise all is well, leave it alone or turn up the radio. Had a 93 850 and a 97 and can't recall ever hearing that noise from the AC. They were both NA's so maybe it is something to do with the turbo engined cars?

Neil.

[abscate]

When you shut off the car it’s normal to hear the refrigerant hissing as the low/ high side of the systems equilibrate.

Abbys car actually sings a bit when this happens, it’s a nice F# tone