Empire

So my girlfriend thought she would be awesome and "top off" the refrigerant in my car.
Problem is, she put too much in and the pressure got too high.
So a day or so later, all of the refrigerant gets blown out of the compressor.

Did something break?
or is that a pressure relief valve?
Is it an actual valve or more of a bust disk type thing?

I attempted to put a little more refrigerant in it to see if I could tell what/where it was blowing out from and I couldn't get a good look at it. It just looks like it is blowing out of the back of the compressor.

I can't get a straight answer from any of the a/c shop people I've talked to about it.

Anyone have any thoughts as to what the problem is?

EDIT: If it makes a difference, it is in my 1990 300zx N/A

Oh, and anyone know anything about changing the expansion valve on these things? I saw a picture of one at the part's store and it was unlike anything I had ever seen before. I figure since I'm gonna be in there working on it, might as well replace it with a new one since it still had the original one in there.

Thanks

johnjohnfourtwenty

The orifice valve in the AC system can get clogged if overfilled and make it so your AC don't work, but the Nissan's use the expansion valve (like most imports) which will work the same as the orifice valve in an AC system. The only difference is it cost more to replace because the expansion valve isn't made out of plastic and screen like the orifice valve.

Edit, I have an AC recharging hose with a gauge on it. is has green for -low, blue for -filled, yellow for -alert and red for -warning. Kinda sucks if your girl had one of these you wouldn't have this problem.

Empire

I kinda figured that's what happened.
So all I need to do is replace that expansion valve and everything will be good again right?
or did something else break in the process?

Yeah, she just used one of those trigger things that come attached to the refrigerant bottles. The green range on those things is pretty significant.

johnjohnfourtwenty

I'd check and make sure your compressor is still working. I doubt it would have got messed up. Also while you have your ac system apart what I've done when replacing orifice valves or expansion valves was taken a air hose and blower, disconnected the lines and blew air though there because sometimes the ac hoses will be filled with some serious gunk.

Oh and the expansion valve should be near the blower motor for the ac.

yeah they take a long time to fill up from low. its quite ridiculous, I did the ac in my old bosses explorer it took almost 15 minutes to fill it up but I changed the orifice and blew out the gunk from the lines. AC blew so cold after that your asscrack would be freezing.

Empire

does that pressure relief valve need to be replaced once it blows open like that? or should it snap shut on its own?

I tried to "test" it by adding a little more refrigerant to the system and it sounds like it is just blowing right out.

Empire

For those playing along at home.
When there is too much pressure in the system, the Pressure Relief Valve (aka Safety Valve) blows and dumps all of the pressure.
This "valve" acts as a burst disk. So when it blows, it needs to be replaced.
It is located on the high pressure line, right next to the compressor.
looks like this...
[ATTACH=CONFIG]156589[/ATTACH]
It is a 16mm
and here you can see the part that blows off.
[ATTACH=CONFIG]156590[/ATTACH]

Calling around, none of the parts stores seem to have it.
Found it on-line here
AC pressure release valve

Appearently, what happens is, r134 runs at a significantly higher pressure than r12 does.
So when my girl was topping off my system, even though her gauge said "green" that was for r134, not r12.
So That's why it burst.
When you convert to r134, this is one of those things that is "supposed" to be replaced, but very rarely ever is.
Most people manage to get away with it because they don't dump enough refrigerant in on top of their old r12 to bump the pressure up that high. they fill til the viewing window shows clear, then they stop. OR they use a manifold that shows both the high side and the low side pressures and stop when the high side starts to get to that "too high" mark.

the nice thing about ordering that safety valve from Z1 Motorsports is that it is a r134 valve. So that solves to pressure differences problem and allows you to actually charge your system completely.

This is the same from the 300zx to the 240sx. I don't know if the replacement part is the same or not, Don't have a 240sx one to compare, but I would venture to say it is the same.

EDIT
here's a picture of a good one and a bad one. (from the bottom)
you can kinda see the piece inside that blows out when the pressure gets too high. The top on is bad. The bottom one is good.
[ATTACH=CONFIG]156591[/ATTACH]

To "test" it. just simply try to blow through it. If it is good, then you won't be able to blow through it at all. If even a little air whistles through, then it is bad and needs to be replaced.

johnjohnfourtwenty

Sweet, hopefully that fixed that problem