[Save-A-Horse]

05 9-3 Linear in Michigan USA
For the last 4-5 years we've had to re-charge w/ R-134a refrigerant every summer due to a slow leak somewhere. This year something has changed. When connecting to the low pressure line to re-charge the gauge reads high at around 75psi. So I discharged the low side from 75 to around 5psi and re-connected the R-134a. This time it accepted the refrigerant (rather quickly), and I stopped around 40psi. AC system still blowing hot air though and when I checked the low pressure line it had climbed back up to 60psi.

It probably goes without saying but I'm not that familiar w/ AC systems.
I did check fuses and swapping relays but the AC unit seems to be running so I'm not really sure what I'm looking for (other than cold air!).
Anything else I should check/try?
Thanks for reading-

 

[Hus_sho]

Does the Compressor clutch engages ?
Does the outside temp reading in the dash reads correctly ?

 

[Save-A-Horse]

Does the Compressor clutch engages ?
Does the outside temp reading in the dash reads correctly ?

Thanks for the questions. Yes, the outside temp reading in the dash reads correctly. I do not notice the clutch engaging however. I swear it did yesterday when I had it down to ~5psi.

 

[Hus_sho]

Do u have a set of manifold gauges or just a low side gauge ?

 

[Save-A-Horse]

Do u have a set of manifold gauges or just a low side gauge ?

Just the low side gauge however I can see if I can borrow a set from Autozone or friends at work.

 

[Hus_sho]

Hock it up while the engine is dead cold and off, read the low side pressure and record the outside temp and post them.
If u have less than 50psi (regardless of temperature) the compressor will not engage, however an optimum charged system will have anywhere between 50 psi @ 55f to 80psi @ 75f (with dead cold engine).
Next start the car and the A/C, note and write the following:
Does the clutch engage ?
Are the cooling fans running ?
Is the pressure dropping in the low side, how much is it ?

 

[Save-A-Horse]

Hock it up while the engine is dead cold and off, read the low side pressure and record the outside temp and post them.
If u have less than 50psi (regardless of temperature) the compressor will not engage, however an optimum charged system will have anywhere between 50 psi @ 55f to 80psi @ 75f (with dead cold engine).
Next start the car and the A/C, note and write the following:
Does the clutch engage ?
Are the cooling fans running ?
Is the pressure dropping in the low side, how much is it ?

Alright so after some investigation I found that the connector to the AC compressor was disconnected (not by me!). Connected it and it definitely engages/disengages w/ the AC button on/off.

It appears there is another problem and that is the hot/cold blend door seems to be stuck on hot. Any advice with this? Checked fuses, look good. I'm not hearing any noise, nothing, when adjusting the dial hot vs cold. Is the temp blend door is on the drivers side? This car does have the "click click click sound when switching the recirculation button on/off but that's on the passenger side.

 

[chasechasechase]

05 9-3 Linear in Michigan USA
For the last 4-5 years we've had to re-charge w/ R-134a refrigerant every summer due to a slow leak somewhere.

Hi Save-A-Horse - I'm very new to the car repair world. Know of someone with an '07 Saab 9-3 that had this same issue (the main sign they said was it would only be a little cold out of the left-side drivers vent as the other vents just blew air that isn't cold).

I have an '08 that now has this issue. I found the below instructions, which make it seem like a very easy repair. Are these instructions accurate / it really is that straightforward to do? Want confirmation before I go ahead and attempt this!

Want to try this before getting more expensive work done on it.

Link to Simple Instructions to ReCharge AC

 

[Hus_sho]

The problem with filling R134a using low side only while not monitoring high side is u could blew something if u dont know what u r doing.
Here is a video using the two port method, u still can use the low side only but at least now u know what pressure values are u looking for, be-aware always perform the procedure on a cold engine.

https://youtu.be/n6oC8JHIdzE

 

[chasechasechase]

Thank you. My main question is in regards to your "always perform the procedure on a cold engine" comment. The video I posted in my last post, says to perform the procedure when the vehicle is at running temperature. Care to elaborate which one is right or if I misinterpreted!

With regards to the video you linked, I think the low pressure location has changed in the 2008 models. The video in my earlier post shows it as a very easy to access port. (Video 3, 7 seconds in).

 

[Hus_sho]

The car in my linked video is a 2008 as well, probably an early 2008 production, but seen both setups on multiple 2008, but the location doesn't change anything.
Let me explain the temperature issue now, let me start by saying the only correct and approved method of filing R134a in modern cars are the weight method which require those expensive machines that recover what ever left in the system and then charge it with an accurate amount according to specs (i think 720gram for the 93), however if u r unable to do that, u can go old school and use the manifold gauges, but to use these u need good knowledge.
How do engineers decide what is the optimum charge weight for any car, is through some tables called saturation tables, which basically tells u what the R134a pressure will be in a system at a certain temperature to achieve saturation (saturation is where gas about to turn liquid, which is not good for the A/C system).
In a perfect world, with the car off and knowing what is temperature of the A/C system u look at the static pressure table and pick the correct pressure value, open the bottle and let the pressure reach that value, problem is, cans will not be able to achieve that high pressure, so u will have to operate the car for the compressor to suck the refrigerant, and for that they developed dynamic pressure saturation tables, basically what values u r looking at on both the low and high side while the system operating at a certain temperature.
U see in all the tables mentioned above, u have to enter with a temperature to find the pressure, now if the engine is hot and thus the whole engine compartment is hot, can u figure out what temperature to use ? While if it was cold, all u have to use is the outside air temperature and as long as u acted quickly when u start the engine this will still be accurate.
I hope that explains it.

First table static pressure (engine cold and off)
Second table dynamic pressure (engine just started and A/C ON)

 

[chasechasechase]

First off, I really appreciate the time you took to give me a detailed explanation. It really explained more of the principles to me and I'm very aware it took you time to type all that out!

I'm between paying $150 for someone else to do this for me, or buying the can and performing it myself, while only monitoring the low side pressure. I think I have a pretty good handle on the operation, but do you think it is worth saving the $110 in savings or are the risks I run doing it myself much greater?

 

[Hus_sho]

Remember Its not rocket science !!
So why not, but let me ask u this, i understand ur A/C is not blowing cold.. but are u sure the problem is low refrigerant ?
If so, then a 1lb can will not cause it to blew .
But then u have to understand, refrigerant doesn't just vanish, and u probably have a leak.
So i would charge the system with a can that has a UV dye in it, so u u have a good chance when it leaks again to find the leak urself and maybe u fix it urself as well and save extra money, as any other repairs on the A/C beside the recharge they will cost extra money.
If u decided to use a can with a dye, expect the dye to leak during filling and contaminate the port surroundings, so i would cover everything around with rags or plastics or whatever, i usually make a hole in a big rag , let the port through the hole, and make sure the rag covers everything and i mean everything .

I always keep a can of that for quick A/C repairs on the shelf