A/C not cooling at all.

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#1
Make
Mercury
Model
Sable LS
Year
2001
Miles
129K
Engine
v6 DOHC
Problem Description: A/C blowing hot air, not cooling. Got home, parked the car and after 2 hours of being parked, I hooked up the gages to it and I got 115psi on the low side and 50psi on the high side. When I turned on the A/C, Low side fluctuates from about 30-50psi, high side staid at ~50psi.

I’m thinking it is the orifice tube (I do not think this model has the expansion valve, or orifice tube IS expansion valve). Any other suggestions? I rather not have to go into the system again. I did change the orifice tube about a year ago, it was TOTALLY clogged, it fixed the problem for about a year, can this part go bad this quick? I changed the clutch on the compressor a year ago also.

Regards,
Bill
 

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#2
Pressures should be roughly the same when not running after 2 hours. Are you sure that the high gauge was reading correctly? Look like it might have not been depressing the schrader valve on the port.
 
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#3
Thanks Bob428. You are right, I borrowed another set of gages from a friend, re-ran my test and the pressure and both High and Low read just about the same after about 2-4 minutes; however, doesn't it seem a little high to you at ~106psi (see attachment) .

So, back to the real issue. I hooked up the second set of meters, and the static pressure was ~106psi. Then I turned on the A/C put it on high, and the temperature set to 60 degrees, of course it still blows hot air. What was interesting is that the compressor kept cycling on and off, with each cycle, The first time the compressor came on, the Low side went from ~106psi to about ~19, and the High side went from 106psi to about 153psi (just for that very first time the compressor kicked in). for all subsequent cycles the low side would go from ~19psi to 40psi, and the High side would go from about ~123psi-127psi, and it would just stay in this mode.

I have a short video, about 22 seconds long, but it is 48Mb big, I do not know the max I can send. Note that the high side only changed about 4-6 degrees each cycle.
 

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#4
You seem to be undercharged. I would recommend that you reclaim the R134a and vacuum down the system. If the vacuum holds, charge the system with the correct amount stated on the sticker. Good luck.
 
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#5
You seem to be undercharged. I would recommend that you reclaim the R134a and vacuum down the system. If the vacuum holds, charge the system with the correct amount stated on the sticker. Good luck.
Thanks for your reply Bob428. So, even though the Low side goes up to 40psi, then drop to 19psi (as the compressor cycled on and off), you think I'm low on refrigerant? I was thinking I have a restriction somewhere (orifice tube maybe). I did use my sniffer to see if I could find a leak but did not find any. May of last year I changed the compressor, the drier, and the orifice tube.

Regards,
Bill
 
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#6
Yes, I still believe you are low on refrigerant. Low side pressure switch is cutting off the compressor until it the pressure goes up. Since I suggest reclaiming refrigerant, you could open the system and examine the orifice tube. If clean, button it back up and evacuate and charge the system.

Good luck.
 

jd

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#7
I think undercharged too. What you could do, is jumper the connector to the two wire Low Pressure Cut Off (LPCO) Switch on the Accumulator. Then see how low the low side goes. I'm guessing it'll go well below 19 and when it does that, look at the Degrees F scale on you blue gauge. It'll be so low in degrees that it's well below freezing. That would freeze the condensate on the evaporator core and stop all cooling since it'd stop air flow over the evaporator.
Your high side of 150 is low for a hot day. The rule of thumb is 2.2 x Ambient Temp, so 90* ambient would be at or a little over 200 psi high side. That, with the low side pulling below 20 psi again suggests undercharged.