AC expansion valve stuck open???

[kuehl]

Okay, J. I won't stop. Most readers know my humor.
I'm not vendoring anything to the OP, just guiding him.
I will send you the bill.

[GreenWater]

If I put more R134a in the system, up to 28oz then the low side will have way too much pressure. Right? or will that be ok? I would guess it will have about 45psi in the low side then. But my high side might be more correct.

I'm ok with the system not being perfect. I just would like it to last as long as possible. So if having a little more refrigerant in the system (and more pressure) is better I can do that. If not I will just leave it the way it is.

[kuehl]

Official TSB 9501 for R134a conversions

944, 83-85/1 is 1020 grams or 36 oz

944, 85/2 + is 860 grams or 30 oz.

9 times out of 10, if you have an issue getting in the specified qty of R134a and all components are working properly (compressor, TEV, condenser and fan) the issue is 'air' in the system.

And, 99.99% of the time if you have air in the system its because the vacuum was inadequate; that means vacuum pump, vacuum oil, system leaks, analog gauges, not following procedures, not understanding procedures, etc.

The other .01% is the 'unknown'.

[kuehl]

Yes, typically both low and high rise with refrigerant qty.
BUT.. I'm more interested in hearing how you fixed the problem; correct pressures.

[GreenWater]

Don't know what I could have done wrong, and I think I got all the air out of the system.

Vacuumed the system for 1 hour, with the gauges attached and both valves open.
Closed the valves and turned off the pump.
Gauges stayed the same for a while.
Unhooked the center hose from the pump.
Hooked in the R134a.
Releases the high side hose from the car.
Opened the high side valve to allow a little pressure into the hose, and releases a little R134a from the hose to clear out any air. (I know I'm no supposed to)
Closed the valve and put the high side hose back onto the car.
Opened the valve for the low side.
Turn the car on, AC on full with button pushed in.
Released the whole can in the system.
Then released about half of another can in the system.
Disconnected everything.

But who knows, maybe my pump isn't good enough or not working right. I'm not sure how I could test that. I don't see what could be wrong. Oh well.

[GreenWater]

The problem is not fixed. I have a reading of Low-35 and High-150

The air is at a temp of about 50 in the vent.

[v2rocket_aka944]

For reference, here is TSB..
http://www.pcarworkshop.com/images/e/eb/Retrofitting_R134a_A-C_1995_680195.pdf

Kuehl, I find this interesting though, I've not seen that TSB before.
However, the sticker on the fender of my early 1985 944 says something like 33oz R-12 charge, so fitting 36oz of R134 would be 10% extra??? That can't be right.

Originally Posted by kuehl

Official TSB 9501 for R134a conversions

944, 83-85/1 is 1020 grams or 36 oz

944, 85/2 + is 860 grams or 30 oz.

9 times out of 10, if you have an issue getting in the specified qty of R134a and all components are working properly (compressor, TEV, condenser and fan) the issue is 'air' in the system.

And, 99.99% of the time if you have air in the system its because the vacuum was inadequate; that means vacuum pump, vacuum oil, system leaks, analog gauges, not following procedures, not understanding procedures, etc.

The other .01% is the 'unknown'.

[kuehl]

I believe the factory R12 sticker on the 85/2 says "33.5" oz R12.
The rule(s) of thumb for R134a conversions can be found to say 80%, 85%, or 90%.
We generally use 85% when the amount is unknown, however adjust the final charge based on P&T (pressures and temperatures).

Hence, the factory TSB states 30 oz R134a for a 33.5 oz R12 system which means they suggested 90%. But once again, we prefer to adjust the final charge based on P&T.

Maybe your 85 has the smaller 10P15E compressor and later condenser and evap,
OR they goofed!

Must be the .01% rule

[Jfrahm]

At what RPM are you measuring pressures and center vent temp? This is usually significant in a 944.

[GreenWater]

Me? I was measuring everything at idle, about 800rpm

I thought I read something about it needing to be at about 1200rpm, but I can't remember now.

[kuehl]

On the 85/2 the factory shop manual suggests, with R12:

at 68F ambient, at 2000 rpms you should have a
low side of 7.25 to 29 psi.
And, a high of 145 to 290 psi

Well, let's see, what that means.
It means if your evap core is at 7.25 psi your evap core is frozen,
even 29 psi with R12 is near freezing
If your high side pressure is anywhere near 290 psi at 2k rpms
on an 68F ambient day, you are gonna toast that compressor sooner
or later when the temps hit 95-100F.

So... close the shop manual and forget you ever read that.


Kyle, if your get bored, follow the procedures suggested and
report back.

Its time go ...... CHRISTMAS SHOPPING!

[v2rocket_aka944]

This was bugging me so I had someone take a photo of the sticker on my car (in another city currently...)

Early 944 called for 40.6 oz of R-12, so Porsche's recommendation of 36oz of R134 makes 89%.


I think the 33 number is for late models, then.

Originally Posted by v2rocket_aka944

For reference, here is TSB..
http://www.pcarworkshop.com/images/e/eb/Retrofitting_R134a_A-C_1995_680195.pdf

Kuehl, I find this interesting though, I've not seen that TSB before.
However, the sticker on the fender of my early 1985 944 says something like 33oz R-12 charge, so fitting 36oz of R134 would be 10% extra??? That can't be right.

Originally Posted by kuehl

I believe the factory R12 sticker on the 85/2 says "33.5" oz R12.
The rule(s) of thumb for R134a conversions can be found to say 80%, 85%, or 90%.
We generally use 85% when the amount is unknown, however adjust the final charge based on P&T (pressures and temperatures).

Hence, the factory TSB states 30 oz R134a for a 33.5 oz R12 system which means they suggested 90%. But once again, we prefer to adjust the final charge based on P&T.

Maybe your 85 has the smaller 10P15E compressor and later condenser and evap,
OR they goofed!

Must be the .01% rule

[GreenWater]

My 87 944 NA sticker says 33.5 oz of R12. Just as a reference.

Thanks for all the help, especially Griff.

I will save your email and used that method next time I work on the AC. For now I'm going to work on other things, I have some oil leaks I need to take care of now.

Before trying this again I will need to buy some better gauges and vacuum pump. (my gauges were readings about 32 for the vacuum. lol. So something is wrong there.

Thanks again!

[John_AZ]

Bookmarked.

J_AZ

[BackyardAC]

The thread/discussion about the stuck open expansion valve. I have the same issues and identical issues. My question is if there is to much oil will this prevent refrigerant flowing thru the condenser. This is what I mean-the high pressure line is hot at the Pump and very warm where it attached /bolted to the condenser but. The condenser is cold. All lines are clear no restriction. System vacuumed down for three hours . High side never gets above 100 psi no matter how much refrigerant I put in the system. Do I have too much oil in the system.??
BackyardAC!

[BackyardAC]

Sorry left off that this is a 1996 Integra ...

[kuehl]

Originally Posted by BackyardAC

My question is if there is to much oil will this prevent refrigerant flowing thru the condenser. This is what I mean-the high pressure line is hot at the Pump and very warm where it attached /bolted to the condenser but. The condenser is cold. All lines are clear no restriction. System vacuumed down for three hours . High side never gets above 100 psi no matter how much refrigerant I put in the system. Do I have too much oil in the system.??
BackyardAC!

Excessive oil tends to saturate (cover) the inside of the evaporator refrigerant tubes and surfaces, which reduces the heat transfer or effectiveness of the evaporator.

Situations where you can have too much refrigerant oil could occur when converting systems from R12 to R134a; you added too much oil to the system. Or, when you have a system with leaks that is refilled often. When a system is refilled or topped off often excessive oil can come from using small cans (12 to 16 oz retail cans) of refrigerant that contains oil (be aware of what you buy, read the can) or if a service tech has injected oil into the system without knowing what was previously in it.
Too many cooks do spoil the soup, and lack of documenting details of AC services, such as noting type of oil, how much, etc. cause issues.

Vehicles prior to 1993/1994 typically used R12 refrigerant which used 'mineral' type refrigerant oil. In older systems the mineral type oil can 'wax' or turn into sludge.
This heavier viscosity can plug up a system and cause high system pressures.
Mixing PAG type oil (typically the 'single end cap' formulations) with old R12 mineral oil can gunk up a system as to two different types of oils don't blend as well as an 'ester' type oil.

Condenser wise, older "tube and fin" coils have larger passages as compared to later serpentine or parallel flow designs. The later two can become clogged, parallel flow more so.

Do you have too much oil in the system is difficult to answer unless you have detailed records of services where everything was well documented.

Sometimes it is smarter to 'bit the bullet' and simply liquid flush the system a refrigerant flush: condenser, remove TEV from evap and flush evap, if you have an accumulator system remove the orifice tube and flush, flush lines, take off compressor and dump oil or disassemble clean and reseal, flush all lines, replace drier or accumulator..... and start off fresh.

[mattdavis11]

If your high side never gets above 100 psi, then either the clutch is not engaging, or the compressor is shot.

What's the low?