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Baffled about a/c operation.

ishrick on Thu October 02, 2008 9:20 PM User is offlineView users profile

Year: 1999
Make: Saab
Model: 9-5
Engine Size: 2.3
Refrigerant Type: r134a
Ambient Temp: 85
Pressure Low: 35
Pressure High: 225
Country of Origin: United States

Okay I have been having problems and this is a short version of what I have done. (a/c works for 15-20 minutes then goes ambient.)

Checked the freon level assuming it was low originally with a shop evac system and it was fine. I evacuated held vacuum for 30 minutes and recharged with 1 lbs 15 oz's of r134a. Which is what came out.
replaced the pressure sensor with new oem sensor. (same problem)
checked heater box blend door operations to make sure climate control was not the problem (all works fine)
The high speed and low speed fans work at factory pressure and engine temp. Engine temp is also normal.

Now with high and low side gauges I have tried to watch the a/c work. at 85 degree's the system had about 100 psi on low and high side.
after cranking the motor the low side immediately goes to 35 psi and the high side climbs rapidly to about 205 then gradually moves to 225 and settles.
the condenser is now hot both fans are on low speed and a/c clutch is of course running without any cycling on or off.
Now this might be a sign of a blockage? but if I bump the rpm to 1000rpms the low side IMMEDIATELY falls to 25 psi and the high side climbs to 250psi, If i hold it the high side will go to 260 psi and low stays at 25 psi
and the high speed cooling fans engage but pressure holds there. letting off the throttle the low side goes immediately to 35 and the high side goes very slowly back down to 225-230 psi. Is this a sign that the expansion valve is clogged? or is that normal for suction to fall drastically?

I did slowly try to bring the charge to 35 on low side with rpm at 1000 but the high side climbed to 270 before the low side reached 35 psi and I thought that seemed pretty high being at 85 degree's ambient. maybe not though. Any advice would be appreciated.

Chick on Thu October 02, 2008 9:54 PM User is offlineView users profile

when you say it goes ambient, do you mean the compressor shuts off?? If not, then when the temp goes ambient, feel the suction line going to the compressor from the evaporator, if it's still very cold, then you have a blend door problem, if the compressor is shutting off and not coming back on, then check the compressor clutch gap.. But as long as the suction line is cold, you have a cold evaporator, and the problem lies elsewhere.. Be sure the condenser is clean of bugs and dirt, and the area between it and the radiator.. Fill the system with the" factory" amount of refrigerant, no more no less..

-------------------------
Chick
Email: Chick

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Freedoms just another word for nothing left to lose

ishrick on Thu October 02, 2008 10:35 PM User is offlineView users profile

sorry I always overlook something lol. Yes the compressor clutch disengages which in short with the complexity of this car shuts off the high speed fans, bumps the idle down via the trionic and basically just goes into econo mode ignoring the fact that it will not be able to maintain 68 degree's in the cabin. If I shut the car off and it sits the a/c works again for a short time. The cooler it is = longer a/c run cycle before it quits. 70 degree's out *not that I need it* the ac will last about 45- 85 minutes 75 degree's it lasts about 30 minutes, 80 degree's = 15-20 minutes and if it goes over 100 it will not work when I start the car. It act's to me like it was overcharged. thus is why I have played with the pressures so much. lower pressure works longer but will only send enough freon to cool 1/2 of the evaporator too low and it doesn't cool at all. I played with it last week too and it was 90 degree's outside. max a/c windows open it was funny it would get ice cold when the highside got to 260 psi low side was about 45. but as soon as the high side reaches 260 psi the dual high speed fans kick on and push the high side to 200 psi. then they shut off and the pressure rises to 260 again and the ac gets ice cold, then the fans kick to high speed and the vents warm, then they go back to low speed and the ac gets ice cold again. about 10 minutes later its like the acc just says fudge it and disengages until I let the car sit. I remember over the past years that it actually worked, if it was hot outside like 90+ it would cycle high to low speed fan every 5 seconds or so if I set in traffic. So maybe I need to go higher up on pressure. it just scared me to go above 45 low side 260 high side. or is on a 90 degree day this normal?

Oh to add I once it shuts down or gives up on the a/c I can go to the a/c relay and jumper it with a decent gauge wire. the clutch engages and the fans kick up to speed, but I do notice a very bad blip in rpm like the car damn near stalls when I do it that way. I think that is because I am bipassing the part where the acc sends a signal to the trionic that the load is about to get big. because when i engage through the a/c the rpm rises right before the a/c clutch engages and you hardly notice any of it. As a matter of fact the high speed fans are the only part of the a/c that is real noticable as they push a lot of air and you can even feel the heat come up beside the car.

Edited: Thu October 02, 2008 at 10:38 PM by ishrick

mk378 on Fri October 03, 2008 1:28 AM User is offline

The refrigerant system is OK. As long as the compressor is engaged, it gets cold. Compressor clutch is OK, as you can jump it. The problem seems to be in the control panel or one of the sensors feeding it. Many digital control panels have a self test function.

tony1963 on Sat October 04, 2008 4:34 PM User is offline

Saabs of this vintage have a habit of the climate control panel going bad. I've replaced probably 25 to 30 on used cars and the AC works fine after that.

I use a company in Massachusetts to rebuild the climate control panels. That does the trick. Very inexpensive, too. Around $100. Takes less than 5 minutes to change.

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Grove Automotive Group, Inc.

An Alabama Corporation

rm32644 on Tue November 18, 2008 12:03 PM User is offlineView users profile

Have you figured out your problem yet? A long shot low confidence comment would be, have you used a different set of gages? Because it sounds like your high pressure is really up around 400 if the clutch is developing that much torque to strain the belt and engine. Plus you have a high pressure shut off switch that is supposed to shut down the system at pressures in the 400 psig range. If the high pressure gage were off 100 psi, all the other symptoms would be consistent with an over charge of refrigerant, or a restricted condenser causing the high pressure.

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