AC Line Frozen. Expansion Valve? Pressure Indicator Switch

50

Asked by Aug 22, 2016 at 10:39 PM about the 2010 Honda Civic LX-S

Question type: Maintenance & Repair

This one is stumping me. I have a 2010 Honda Civic
LX-S. The big AC line is frozen. Which would
indicate the expansion valve is the issue or so I
have been told. The big problem is that pressure is
building up so much that the freon fires out near the
bottom. So there must be a blockage of some kind.
The compressor was replaced with a brand new
one a year ago. That checked out. We replaced the
AC relay when the fans were not engaging. Now
they work. And the pressure still fires out. The high
pressure is something like 400 when there is that
pressure release to protect the compressor. Now,
my mechanic, a very smart guy whose never been
wrong before, is telling me it's not the expansion
valve bc he checked it. He seems to think it is the
pressure indicator switch. I asked a Honda tech
friend of mine. He seems to think there's a
restriction in the line and it has to be the expansion
valve. So since the current mechanic is truly not an
idiot, then why does he think a) it's the pressure
indicator switch, b) COULD it be the pressure
indicator switch and c) what do you think the real
problem is?

As I mentioned the condenser was replaced a year
ago and seems like it's working fine as this issue
with the AC line freezing is recent.

12 Answers

62,185

This is caused by blockage in the lines,or bad high or low pressure switch which controls the compressor and tells it when to cut off,if bad will continue to run and biuld pressure and blow out at the releif valve,check the pressure switches,one or the other is bad more than likely.

50

So it really is one or the other? The expansion valve blockage makes sense but if the pressure builds up and the indicator switch doesn't engage then of course the pressure will shoot out. However would the pressure indicator not turning on to relieve the pressure cause the pipe to freeze over?

1 out of 1 people think this is helpful.
62,185

Two things will make it freeze up,a blockage,or it not cutting off when it biulds up to the right pressure,The expansion valve is not your issue,have worked on many of them and i think your high pressure switch is bad making the ac run more than needed,and this is the what is causing the issue if they vacumed the AC right they could tell if there was blockage.

50

Ok, I'm learning so forgive me if I'm sounded repetitive: if the AC pressure indicator switch is bad then that means the AC is running more than it needs to. By doing so, it is causing the line to freeze up, which is causing a blockage and the pressure release valve is dumping freon to free up the pressure?

1 out of 1 people think this is helpful.
62,185

Yes the pressure switches are made to save your compressor from damage,

62,185

If it is bad,it will not shut the ac off,and puuuuufff,there goes your freon.

50

Gotcha. So I guess my mechanic then might be right. It's been stumping him as to why the pressure kept releasing and the line was freezing up. I figured it was the expansion valve too but he said he checked it. I guess it has to be the pressure switch

1 out of 1 people think this is helpful.
62,185

I agree,

50

What about a restriction in the orifice tube?

1 out of 1 people think this is helpful.
50

The other thing is when I pour hot water on the frozen AC line it starts to work again for a little while then of course freezes up. Usually there's the first pressure release within an hour then the second happens a lot later, both while the car is idling. Mechanic had it idiling for an hour once no problems. I take off with it, drive around for an hour, the pressure burst/release happens.

1 out of 1 people think this is helpful.
62,185

The freezing is caused by to much pressure,and would be worse when driven being the compressor is pumping faster,have them pull a vacume on it,this will rule out blockage,it is frezzing on the high pressure line because it is not cutting off,the vacume will not pull if clogged line,

50

Today it happened super fast. The car was idling, the mechanic was trying to move the car around as car were blocking it. AC was on I think. I geared it, drive maybe 200 yards, stopped at the stop sign, looked for the radio code for 2 minutes max and boom, freon pressure release. So I wasn't even driving it an hour today. Like 5-10 minutes. Everytime it has happened it has been when the car was sitting idle.

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