Hissing sound from Air Conditioner on 97 Accord

Sure you don't have a snake trapped in there?

You're probably just hearing the vacuum activated dampers & flaps moving into place. If it hisses periodically after you start it going, it could be a vacuum leak or an intermittent contact in the switch.

Check that the radiator (not just the overflow tank) is full to eliminate the possibility of air bubbles in the coolant moving through the heater core. It could also mean the charge in your AC is not right, in which case you're hearing the fluid/gas bubbling through.

Get somebody familiar with that model car to listen to it. Someone who works on these things for a living will recognize your hiss instantly and be able to tell you if its a problem or just the nature of your car.

The area behind the glove box is right where the A/C expansion valve resides on your Accord. You are just hearing the sound of refrigerant changing states from liquid to gas through the expansion valve (it is a designed-in restriction). IOW, it's normal. If the A/C system wasn't cooling properly in high temps and the refrigerant charge was full, then an excessive hissing noise near the glove box would lead me to believe that the expansion valve was stuck closed - also verifiable with pressure gauges. You have proven that this is not an issue by stating that you have adequate cooling in high temp weather.

Toyota MDT in MO

We recently replaced a compressor, drier and expansion valve on a Honda CRV. Had to warranty the damn expansion valve because it made a piercing whistle! All the while cooling just fine. Thank the good lord Jap evaporator boxes come out in 20 minutes as opposed to 6-10 hours like on some domestic vehicles.

Don

Apparently the Japanese have a different lord when it comes to under dash service. Was this a Nippon Denso or Honda OEM TXV ... or an aftermarket unit?

Toyota MDT in MO

Its probably getting slightly low on refrigerant. IF it hisses shortly after the compressor cycles on, its probably a frothy mix of liquid and gas passing through the expansion valve rather than pure liquid as is normally the case. Nothing to worry about- ALL auto air-conditioners gradually lose charge around the compressor shaft seal. Its only a problem if it starts losing charge rapidly to the point it needs a recharge more often than every few years.

Thank the good

Just for that anti-American remark, I'm bringing YOU my wife's 93 LH car the next time it needs that job. After all, you're only 5 minutes away from me :-p

I didn't mention heater cores. Heater core removal can really suck on some domestic vehicles. It can really suck even worse on most ALL Japanese vehicles. Good thing the Jap heater cores rarely fail!

Don

It was an aftermarket "AIR" brand from WorldPac. Perfect physical fit, proper pressures but developed an intolerable whisle about two days after the car was picked up.

Don

Don won't mind. After all, it will be on the clock...

JT

I suspected as much, but in reality I have no experience with aftermarket A/C parts on Japanese vehicles. I've always used Toyota/ Honda HVAC parts in the dealers I worked at as well as for indie/home jobs. It sounds like the high pressure passageway was crimped but not blocked, or maybe some manufacturing flash was stuck in the path.

Toyota MDT in MO

Don wrote in news: snipped-for-privacy@4ax.com:

Heater core removal didn't suck on my '75 Corolla. It was pretty easy, in fact.

The big problem with those puppies was that the heater control valve was inside the passenger compartment, right above the gas pedal. And they LEAKED. The damned thing's seals had the sort of lifespan enjoyed by tadpoles once seagulls have discovered where they are.

Japanese cars didn't start out as good as they are now. Ask me how I know.

innews: snipped-for-privacy@4ax.com:

The 83-87 Renault Alliance/Encore design dispensed with all of that interior heater control valve crap, and instead opted for a heater core that leaked in about 99.9% of all cases. (Dash removal required) Ask owner's legs how they know...

Toyota MDT in MO

In my exprience, if you use good antifreeze and change it on schedule... NO heater cores are very prone to fail. I think I've had excatly one that ever developed a problem, and that was after 36 years of use.

.... and now they own Nissan.