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Having problems, have a few questions

salth2oj on Thu June 24, 2010 8:51 PM User is offline

Year: 1999
Make: Saab
Model: 9-3 convertible
Engine Size: 2.0
Refrigerant Type: r134a
Ambient Temp: 85
Pressure Low: 48
Pressure High: 225
Country of Origin: United States

Hello-
I just purchased a used 9-3 Saab and after addressing a few other issues I have moved unto trying to solve the A/C problem.
The first problem I ran into was the compressor would not come on. I found there was no pressure in the system, after adding two 12oz (one with the UV die) cans of r134a the compressor started and I got warm (64f) air coming out of the vents. This was a small short lived victory.
With-in a week, the compressor would no longer come on; I found a leak in the high pressure hose (from the compressor to the condenser), found a junk yard replacement and installed the following weekend. A new drier was also installed.
I evacuated the system for about 20mins and this was followed by watching the gauge to see if I lost any vacuum for the next two hours. All looked great.
I followed this up with 770 grams (per the label) of R134A. The site glass was bubble free, the low pressure line (go back to the compressor) had lots on condensation on it. The LP was 48 and the HP was 225 (with needle jumping a little) on a 87 degree day. The problem is, the air coming out of the vent was only 65 degrees.

Questions and comments:
Is the LP a little on the high side?
It seems that the HP might be a little on the low side.
I’m thinking either a failed compressor or a failed expansion valve.
With the system NOT running, I had a pressure of 72 on the low side and about the same in the high side. This was a 70 degree morning.

Thanks
Jim

salth2oj on Sat June 26, 2010 6:37 AM User is offline

Follow up question, a easy one for you guys.
when "taking" reading on the gauges, at what RPM should the motor be at?
I took the ones in my post at idle (850-900 rpm) but i think i read somewhere the engine should be at 1200-1500 rpm. If that is the case, I might be a little off on the numbers posted.

Briandl79 on Sat June 26, 2010 5:22 PM User is offline

This makes me wonder, so I'll add this question to your post for the experts: Is it a good idea to simply fill the required amount, or is it a better idea to fill close to the required amount, say in this case 24 oz (two cans), then check the temps, and if they are where they should be leave it alone, or if not fill the rest slowly while keeping an eye on temps?

TRB on Sat June 26, 2010 5:43 PM User is offlineView users profile

Quote
Originally posted by: Briandl79
This makes me wonder, so I'll add this question to your post for the experts: Is it a good idea to simply fill the required amount, or is it a better idea to fill close to the required amount, say in this case 24 oz (two cans), then check the temps, and if they are where they should be leave it alone, or if not fill the rest slowly while keeping an eye on temps?

When using the OEM refrigerant type for the vehicle it's always best to try and have the factory charge level in the system. When they design a system they decide on a charge level which is best for all climates. If you have a proper charge level and have odd pressure or cooling. That the time to find the reason for said issues.



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Briandl79 on Sat June 26, 2010 5:53 PM User is offline

Well the low side seems a little high generally speaking, although I don't know much about SAAB's. So in this case are you saying it's highly unlikely his problem is too much refrigerant? If so what's the likely culprit, TEV problems, or maybe not enough vacuum drawn?

bohica2xo on Sun June 27, 2010 3:05 AM User is offline

You have a sanden scroll compressor. They tend to have poor output at idle, which does not improve with use.

You should test that system @ 2000 engine rpm, cabin fan on highest speed, doors open. Run for 5 minutes to stabilize, then record pressures while engine is still turning 2000 rpm.

Post the results.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

salth2oj on Mon June 28, 2010 6:45 AM User is offline

I was able to spend some more time checking out the A/C pressures, some interesting finds.
Once the engine was increased to about 1500 RPMs, the pressures started to look normal. It was a 90 degree day and I had 28/225 and the center vent temp was 54. As I increased the RPMs the lower the low pressure went and would see a small increase on the high side, I believe this is normal and correct. I think at one point I had 24/235, but I was unable to get the vent temp any lower then 53.

The other interesting find, I'm able to get a lower vent temp when the fan speed is on "2" then when it is on the highest setting of "4". Is this a clue to my problems?
I would think I should be able to get the vent temp into the 40's. Any ideas?
Jim

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