Check my logic: Car A/C issue
 

So my Saab A/C is blowing hot, and the Saab BBSs suck. I turn to the braintrust at Pelican.....

Compressor engages, ACC shows zero faults, evaporator fan engages, evaporator looks clean and intact, flapper door moves as it should. Blower air is about ambient, larger return hose is warm. Compressor is 50k and 4 years old. Freon was drained, vacuumed down for 30 min, then recharged. Approximately 40 psi low and 180 psi high, at about 90 deg ambient. Several hoses have been replaced, it seems to hold pressure just fine.

My only thought is that I f'ed it up by adding a couple cans of freon prior to picking up the gauges. Wal Mart stuff, I think it had oil and stop leak in it. When I hooked up the good gauges, I found that the low side was about 55 psi. I drained and vacuumed the system, but possibly some of the crap from the Wal Mart stuff did damage?

My thought is the expansion valve. From my reading, it can cause similar issues to what I'm seeing. Everything else seems to be working fine. Am I on the right track?

Pressures should be equal with car shut off after sitting awhile. Upon star up and AC on, I would think low side should be somewhere in the 15-35 psi range and high pressures 150+. You stated your low is now reading 55psi when AC is on or is it still the 40/180 type figures. I don't know the "normal pressures for your car, but at 40/180, I would think you would be seeing some sort of "cool" air at your vents. The pressure differential bewteen your 40/180 numbers would lead me to believe your compressor is functioning.... maybe the tiny orifice in your expansion valve is plugged???

Sounds like the expansion valve to me.

Doubt it was freon, was R-134a, I assume.

Most recommend staying away from the stop leak and oil stuff.

Did you have it vacuumed down after you put this stuff in?

Did you vacuum it yourself? Most 'home' pumps can't pull enough vacuum to be effective. You may still have air and moisture in there.

Expansion valve would also be suspect.

BTW, the compressor/system on my 91 SPG was trouble-free for over 100k miles, needed a couple belts, though.

Tim, I had initially overcharged it, thinking it was low on freon (i.e. R134a to make tcar happy). The current charge is 40/180.

tcar, I vacuumed it down after overcharging with the cheap stuff. I vacuumed down to 30 in HG, and held it for 30 min. It's a pretty powerful pump, my dad made it out of a refridgerator compressor and some sort of motor. I then charged to the current 40/180.

Did you vacuum it down, and then shut the pump off and wait 30 minutes before charging? Or did you keep vacuuming for 30 minutes after it reached 30 HG?

Try posting here: Moderators are good about responding quickly to questions.

http://www.autoacforum.com/categories.cfm?catid=2

You have a block style valve. Make sure you get the right one. Picture point of reference is seen looking from the front of the car. http://forums.pelicanparts.com/uploa...1214658942.gif

I don't know much about the saab and how the a/c lines are run, but you have another solenoid valve for the rear a/c. Does it blow cold back there? I'm not sure if the solenoid valve cuts off the air flow or refrigerant. Usually with dual air, you have two expansion valves, or an orifce tube in front and expansion in rear, or an auxillary valve. You do have an expansion valve in the front, no doubts about that.

Huh...... typed the above about 1/2 hr after downing just one triple Vodka/DietCoke after a bad Friday at work. Interesting to see the effect on my grammar and typing. :o:D


Matt, after thinking about this a bit, your problem is a bit odd to me as a plugged expansion valve would typically create very high pressure on the "high" side and very low pressure on the "low" side.

Are you getting even cool air in the vents? If so, maybe you simply need more 134. Sorry for the lack of a definitive answer.... I have ressurected several old non-operational auto AC systems in my old German cars, but I am no expert.

Tim the pressures could be right if he has a valve in the rear, and he does, I'm just not sure what function it serves, ie. air or refrigerant cut off.

I'm no expert, but I am in the automotive a/c business.

Yep it regulates refrigerant just like an expansion valve or orifice tube.

I vacuumed for 30 min, but turned it off and let it sit to ensure that it held vacuum.

Matt, that's the correct expansion valve for the front, but I don't have one in the rear. That's an option for the 9000, mine does not have it.

Tim, the low side line is warm, vent air does not appear to be cooler. Thermometer indicates it's about ambient coming out of vents.

So right now, I'm planning on replacing the expansion valve, then vacuuming down and recharging. Obviously I'd have to anyway after opening the system. It's only $28, and pretty much the only thing I can think of.

Expansion valves clog, but you can remedy the situtation with a back flush, sometimes. If it's clogged, there was trash in the system that clogged it. There is no if ands or buts about it. You need to clean the lines!

New expansion valve is on order. Matt, any details on how to clean the lines?

They sell AC flush at most auto parts stores, I had a clogged orifice tube this weekend on a customer car, I just removed all of the lines from the engine compartment and flushed them on the bench. I flushed the evap and condenser with cleaner and compressed air.

You actually have to remove the parts?! I thought they had flush products that you sucked through the system?

Not sure I get this part. There is no specific gauge pressures for initial charging 134. You have to add the correct amount to start with. You don't keep charging until you reach a gauge amount. At rest, both sides should be equal, @ 120 psi. What are reading at rest?

What I had read online was that recommended low side pressure should be 24-45 psi, so that's what I charged to. After further reading, I realize now that I should have charged by oz of freon, which I will do the next time.

They do, however I found metal bits in the orifice tube so I wanted to be sure. This car had to have a compressor and it was very expensive, on top of that it was an R12 job so I wasn't going to cut any corners.

I'd ask here

ACKITS.com

At 40 psi your evaporator is at 45 degrees.