I've recently noticed a hissing noise coming intermittently from my evaporator when I have the A/C on and am wondering if anyone knows the cause. My idle also seems to bog down at idle then go back to normal when the compressor kicks on; it seems like it does this more than it should. The A/C blows cold with no problems.

Here's what I think it may be:
1.) Low refrigerant level
2.) Expansion Valve
3.) I need a new drive belt or it needs to be tightened.

Any input would be appreciated. This is a completely stock system in a completely stock 99 EM1.

 

See if you can determine it to be a internal hiss, there is a pressure relief valve in the system to prevent over pressurizing the refrigerant, that could be the cause. I would check your refrigerant pressures with a gauge to see if you are overfilled or underfilled, A/C work is not cheap.

Compressor kick-on time is usually for 10 secs or so, with a 5 sec down time, and then back to work it goes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">See if you can determine it to be a internal hiss, there is a pressure relief valve in the system to prevent over pressurizing the refrigerant, that could be the cause. I would check your refrigerant pressures with a gauge to see if you are overfilled or underfilled, A/C work is not cheap.

Compressor kick-on time is usually for 10 secs or so, with a 5 sec down time, and then back to work it goes.</TD></TR></TABLE>

Good stuff, I was going to check the pressure on the lines anyways to be sure. Thanks!

 

Anybody know what the high / low pressure readings should be?

 

Let me be more specific, it kind of sounds like water bubbling and steaming and I know it's coming from the evaporator.

I'm thinking bad expansion valve or low coolant. Air is now not as cool as when I bought the car. I also found out that you cannot acquire refrigerant in WI without a license, so I'm prepared to get bent over to get it recharged.

Any input is appreciated.