AC expansion valve stuck open???

[GreenWater]

9FF. I did a google search and figured out where it was, then it was easy (kind of). Take the cover off the blower fans and it's on the left side, under the flap. Clip the plastic squares off and then it's right there. But the darn coil was a real pain to remove, and now a pain to get back on.

[kuehl]

Expansion valves can get stuck open, partially open or fully closed.
All it takes is enough moisture in the system and it freezes inside the valve.

Excessive refrigerant oil is not your problem.

Whom evacuated and charged the system?
How much refrigerant in total did they put in?

[GreenWater]

Problem is fixed now.

The coil on the expansion valve was the biggest pain to get reinstalled. !!! Don't take that out unless you really have to.

I put everything black together and tried a few things with the schrader valve. But still no refrigerant would enter the system. Then I had the idea of taking an R134a adaptor and just plugging that onto my AC hose. And what do you know, nothing would come out. So there was something wrong with the way my hose attached to the R134a adaptor. I had to push the two together with my hand really hard and then refrigerant would enter the system. !!!!! That was my whole problem. LOL

Now the AC feels cold, but the reading seem a little off still.
Low 50
High 125
Temp outside about 70 with 80% humidity

[kuehl]

Great to hear you found part of the problem.


Now that you have figured how the issue with the connections, maybe...?
If you have R134a charge port adapters on your old R12 service fittings you need to insure what kind they are. One type of adapter has a pin that pushes down on the schrader valve inside the old R12 service port. Another type of adapter has its own schrader valve and this means you have to remove the old schrader valve from the R12 service port before you install the R134a adapter on it.

There are 2 types of 'snap on' service hose couplers that you can put on your R134a service port adapters. One is simple like an air tool hose coupling, you simply pull back on its outer shell, put the coupler on the R134a adapter and release the shell. This type automatically pushes down on the valve or pin in the R134a adapter. The second type of coupler has a knob on the top. You turn the knob outward (CCW), pull back on the outer shell, put the coupler on the R134a adapter, release the shell, and then turn the knob inward (CW) and this knob moves a pin inside the coupler to push down on the pin or valve inside the R134a adapter.

Assuming you have the engine warmed up, at "idle", ac running for at least 10 minutes or so, windows up, temp set to max cold, no fresh air mixing with the AC air, ac fan speed 1 or 2, at 70F outside air temp:

1) You would expect to a high side more near 160 psi. You are seeing 125 psi. If you have a good compressor your present high side pressure suggests you are undercharged, not enough refrigerant.

2) Your low side, in a perfect world, would be 35 psi or near there with everything operating correctly; low side in a properly evacuated and charged system with 35 psi would reflect an evaporator core temperature of approx 37F.
You are seeing 50 psi which would reflect an evaporator core temperature of 45F . Usually, your AC vent temperature will be a few degrees warmer than the evaporator core temp. You can verify the AC vent temp using a digital thermometer in the vent, or if you can access the evaporator core you can put a probe in its fins.

Because of your low high side reading and high low side reading it sounds like you are undercharged and you have 'air' in the system. So, back to the original questions:

A)Whom evacuated and charged the system?
B) How much refrigerant in total did they put in?

If you do not pull a 'perfect vacuum', remove as much ambient gases (air) from the system, say down to 30" of mercury for simple terms, the excess air still in the system will prevent the refrigerant from operating correctly. Excessive air contains moisture. Moisture can freeze inside the expansion valve and cause a blockage, cause it to hang open or stay closed.

After you pull that perfect vacuum you need to have a idea (a bogey) of how much refrigerant your system needs to work properly. Let's say your 944 in the past used 2.25 lbs of R12 refrigerant; lets convert the rough pound measurement to ounces, 2.25 x 16 = 36 oz of R12 (you might have a refrigerant sticker somewhere in the engine compartment noting exactly how much). With R134a we usually use less refrigerant. A rough idea is 85% of the weight of what you had with R12.
So .85 X 36 would be about 30 weighted ounces. That is your bogey.

As you charge the system you have to observe and record how much refrigerant you are putting in. So, for example if you knew you put in the "bogey", or 30 oz in this example. And the outside air temp is 70F, and your low side pressure is too high, 50 psi, and your high side is too low, 125 psi That would suggest your compressor is weak (excessive slop in the piston/bores, problem with reed valve).

And, I'm assuming the observations of temperature and pressures you noted were when the compressor was operating; not static.

So, if you think you got your service hose coupler thing figured out, and you know whether or not someone pulled a good vacuum before they charged it.....
What do you think the issue is?

AC Help Basics

[v2rocket_aka944]

[Bradical]

I agree with Kuehl, but if you have air in the system from a bad evacuation it will cause your head pressure to be elevated as well in most cases as well. I am sure it's air if you did not pull an effective vacuum on the system before charging. However- Elevated suction is typically indicative of elevated heat load (or humidity load, both take up system cooling capacity) coupled with that the compressor is at somewhat of a reduced compression ratio at idle.

If I had to guess... The suction reading is wrong, and actually lower, and the whole system is alittle undercharged.

[Bradical]

Originally Posted by kuehl

Expansion valves can get stuck open, partially open or fully closed.
All it takes is enough moisture in the system and it freezes inside the valve.

Excessive refrigerant oil is not your problem.

Whom evacuated and charged the system?
How much refrigerant in total did they put in?

...stuck open from moisture freezing in the valve, that would be interesting. A solid peice of ice strong enough to act against the spring pressure and suction pressure which act to drive the valve closed. I'd hope with that much air in the system it would trip on high head pressure or clog the filter drier first. Have you actually witnessed that happen before? I am not trying to be arguementative or negative or anything like that, as I mentioned before I do commercial HVAc so I've only done automotive AC as a hobby, I am genuinely interested to know if thats something you have seen before?

I am sure if you do auto AC you probably deal with excessive moisure all the time from people without recovery/evac equipment doing home repairs, its not something that I see alot in my work. Maybe once a year.

[kuehl]

Brad,

Is the bass fishing really as good as they claim down by you?

Back on the topic of the moderator's initial post.... my 2 cents are based upon the initial symptoms and events and his observed gauge readings: probability of ambient gases in the system and an undercharge. If you and I had been sitting there observing the procedures he undertook we might arrive at a different conclusion.

Have I seen TEV's (expansion valves) malfunction because of moisture? Yup.
How often have I observed this in the past 30 years? Hands on working with client's vehicles at our shop, at least twice per year but more common on with 911 and 930's because they have 40 feet of hose and 2 condensers. Helping 'experienced' auto repair shops trouble shoot the same issue over the phone, at least 6 times per year. Helping DIY's over the phone, a dozen times per year. Why does this happen? Well, with the experienced auto tech's many don't realize the volume of the system, say on a 911/930, and the need to purge with nitrogen or refrigerant gas a few times in the evacuation process. With DIY's the causes vary between simply not pulling a vacuum, use of inexpensive equipment (faulty gauges, service set's with loose connections or leaks), not understanding how the service set works, failing to install an o-ring or shearing an o-ring, allowing air to enter the service set while swapping cans, etc.

Getting back to the pressure differentials observed, 50/120 at 70F relative to an automotive system, and assuming the gauge readings are correct (user knows how to use the service set), and assuming the new compressor is good: the system in undercharge and likely has ambient gases (air) inside. But, you never know.
I've seen client's (experienced tech's and DIY's) call us back a week later "Oh, hey, my bad, I installed that new compressor you shipped down and it was not the compressor".

We don't do home, commercial or industrial systems normally, but I have helped a few people along the way, such as last year when the local HVAC guy left 2 kids at my place to finish off installation of a new comp/cond unit outside my place; the 2 kids did not realize the unit arrives with a charge, and amusingly the 'object' they found in the old cabinet, left by the previous service tech was his electronic sniffer!

Cheers,
Griff

[GreenWater]

Thanks for all the help guys, I appreciate it.

Here is what I'm doing, and you are probably going to hate it. lol. I'm trying to use hydrocarbon refrigerant instead of R134a. And this just might be my whole problem.

I have used this stuff before and it worked great. But this time, not so well.

They state on their website, many times, to NOT pull a vacuum on the system before installing it, so I didn't (which sounds really wrong to me). But I do have a vacuum pump so I am able to do this.

They say to use much less than you would R134a. I installed 2 cans which is the same as 32oz, and my sticker says the system uses 30oz, but the readings were still not good so I added more, and now I have what I said before.

My gauges are not super cheap ones, but not really expensive ones either. They are the push on couplers like an air compressor (more or less). Not the screw type.

The R134a adaptor that I have on the car now does require me to remove the R12 valve stem, and it is removed. I noticed the 2 different styles.

My compressor is a brand new unit, so I would have to assume it's good, unless I did something to ruin it.

I'm thinking I should get the hydrocarbon refrigerant out of the system and evac, and install R134a. And I'm guessing that's what you are going to advise too.?

[kuehl]

Originally Posted by GreenWater

I'm trying to use hydrocarbon refrigerant instead of R134a.
They state on their website, many times, to NOT pull a vacuum on the system before installing it

OMG !

OHHHHH !

Well, we don't use hydrocarbon based refrigerants, for legal and other safety reasons.

But..... many of the brands do suggest pulling down a vacuum, to what level depends upon the brand. And in terms of qty and pressures.... we will toss out the refrigerant weight and pressures comments.

Have fun!

[GreenWater]

LOL, I like to try new and different things. I think it's fun and interesting. But it also gets me in trouble a lot, and makes my life harder. Maybe one day I will learn.

So I will get rid of the hydrocarbons and pull a vacuum and use R134a and let you know what I get from that. Hopefully it will be more conventional.

[kuehl]

Kinda of reminds me of the story:

Wife: "Oh, I forgot to tell you, the car is running funny".
Husband: "What do you mean?"
Wife: "There is funny noise coming from the front"
Husband: "What do you mean, where?"
Wife: "What do you call it, the hood? Sounds like a cement mixer".
Husband: "When did the noise start".
Wife: "Oh, I guess it was a month ago, but I did not want to bother you, I know you are busy. Oh, and there is a little red light on the dash, it says 'oil'".

[Jfrahm]

Why are you reminded of this story?

[kuehl]

[Jfrahm]

It just seems grossly unflattering the the OP is all. I mean the story involves someone overlooking an obvious scary noise and and idiot light for stupid reasons. OP had a schrader valve and R134A adapter problem in an auto AC system, I do not understand the comparison unless it's meant to be insulting and implies the OP's problem was obvious.

[GreenWater]

All that aside. Here is where I am at now.

Pulled a vacuum on the system for 1 hour, and the gauges read past the 30 mark.
Left it sit for a while and the gauges still read the same. No leaks. (that's good news at least)
Put 12oz of R134a in the system. Gauges read Low-30 High-125
Put another 6 oz in (18oz total) and the gauges read Low-35 High-150
Temp outside is 70 with 70% humidity (feels hot to me)
Static reading is about 83 on both gauges
Temp reading at the center air vent is about 50 degrees. It feels very cold to me.

The car sticker says 33.5 oz of R12 is needed. But if I put more in the system the low side will be too high.

It feels great to me the way it is right now.

The compressor is new, but my reading would say I have a weak compressor, right? What will happen if I just leave my car the way it is right now?

[kuehl]

Well, most posts are "light" here.
If the moderator finds it offensive let the moderator address that issue.
But, if you want to be hall moderator for the week, go for it.

[v2rocket_aka944]

R134 should be 75-80% of the specified R12 charge, is what I've always heard and used over the years. So a late 944 about 24oz = 2 typical cans of R134.

I'm sure Kuehl can give a better estimate.

[Jfrahm]

I do not want to be moderator and I did not say you should stop. I just thought it was out of left field and I was either confused about what you were on about, or surprised that a vendor would insult someone like that. I thought it was worth clarifying. Thanks for clearing it up. I guess.

-Joel.

Originally Posted by kuehl

Well, most posts are "light" here.
If the moderator finds it offensive let the moderator address that issue.
But, if you want to be hall moderator for the week, go for it.

[kuehl]

If this is R12 or R134a, at 70F you would prefer to see around 160 'ish' on your high.
Again, looking at a bogey, if R12 was 33.5 then with R134a should be about 28 oz by weight. You got 18? You are severely undercharged.

The 50 low is baffling, but for the moment.

I would not blame the compressor just yet. But, did it come in a Denso box? New?

Will operating this system with an undercharge hurt things. Yes, possibly the compressor over time. Compressors need a reasonable amount of refrigerant flow to stay lubricated; the refrigerant carries the refrigerant oil through the system.

Side note: On testing for leaks, pulling a vacuum down to 30" is just a test for gross leaks (big leaks). Your system can run up to 250 psi easily on a 100F day.
30" of mercury is equal to 14.7 psi. The best 'testing' is with an electronic leak detector. Next best is dye and a black light however limited to what you can see.