ChrisBuck

I have had a intermittent hissing sound from the AC since the truck was new (today 5 months and 16,500 miles). It only occurs when the blower is set on 1 or 2. It is only noticeable when the AC temperature knob is on cool side of the dial. The hiss sounds like a solenoid venting. It lasts for 2-5 seconds, and repeats every 30 to 40 seconds. Since it is a soft noise I have learned to live with it. I had taken it to the dealer who told me this is the way Nissan ACs are designed. Has anyone else experienced this, ...or is this the way Nissan ACs are designed?

tobybucksnort

I am a a/c service tech,the sound you hear is the freon changing state(liqiud to gas) through your metering device located in the evaporator.the reason it sound is louder on lower fan speeds is that the slower the air passes across the evaporator coil,the quicker it takes off latent heat(slower fan=cooler air)although you may need to check freon charge if cooling declines or hiss becomes more frequent,It would indicate low freon charge, being a leak or not charged properly from the factory.Hope it helps..

msubullyfan

I can hear the coolant hissing as it expands across the throttle valve in my truck, too. It's certainly more pronounced than most of my other vehicles have been, but it isn't really too annoying.

The expansion noise on my Mitsubishi Montero Sport was horrible after they replaced it... never could get it to stop.