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What are these AC pressures telling me? #4446731
07/01/17 02:16 PM
07/01/17 02:16 PM
Joined: Jan 2007
Posts: 833
El Oeste
HawkeyeScott Offline OP
HawkeyeScott  Offline OP

Joined: Jan 2007
Posts: 833
El Oeste
This is the wife's 2007 Chrysler Pacifica 4.0 with original AC system components. Seemed to cool rather poorly just as the summer began. It blew some cool air but it was definitely under performing. But, just in the last week or so, it seems to have improved on its own. It's not the coldest it's ever been, but it's not bad.

I put gauges on it today. It was 85 degrees out. At idle, the low side read about 19 and the high side ranged from about 240 to 255. Then, at about 2500 rpm, the high side would surge to 325 with the low side pretty much staying put.

Based on what I see online, the low side is a little low at idle and the high side is normal. But at higher RPMs, the low side remains low while the high side is very high. Again, though, the system is putting out a fair amount of cool air.

Blockage? Dying component? Investigate more? Leave it alone? Thanks.


Last edited by HawkeyeScott; 07/01/17 02:19 PM.
Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446742
07/01/17 02:23 PM
07/01/17 02:23 PM
Joined: May 2010
Posts: 9,856
out there
spasm3 Offline
spasm3  Offline

Joined: May 2010
Posts: 9,856
out there
Does the fan work? Condenser clean ? 19 on the low side may be a bit undercharged.

Last edited by spasm3; 07/01/17 02:23 PM.

13 elantra 75k 5w30 QSUD
03 chevy avalanche 80k synpwr 5w30
17 mazda cx-5 9500 miles m1 0w30
Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446745
07/01/17 02:25 PM
07/01/17 02:25 PM
Joined: Jan 2007
Posts: 833
El Oeste
HawkeyeScott Offline OP
HawkeyeScott  Offline OP

Joined: Jan 2007
Posts: 833
El Oeste
Yep, both fans are running and the condenser is clean.

Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446753
07/01/17 02:32 PM
07/01/17 02:32 PM
Joined: Jun 2003
Posts: 18,416
Deplorable in apple valley, ca
Chris142 Offline
Chris142  Offline

Joined: Jun 2003
Posts: 18,416
Deplorable in apple valley, ca
Has anyone added refrigerant?


02 Wrangler carlube 5w30
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Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446761
07/01/17 02:41 PM
07/01/17 02:41 PM
Joined: Nov 2007
Posts: 258
Richmond, VA
DNVDMAX Offline
DNVDMAX  Offline

Joined: Nov 2007
Posts: 258
Richmond, VA
Debris possibly blocking orifice tube or expansion valve.


06 GMC 2500HD DMAX EFILIVE M1 TDT 5w-40 FRAM Ultra
91 GMC K1500 5.7L 5w-30 Quaker State HM Bosch D+
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Re: What are these AC pressures telling me? [Re: DNVDMAX] #4446762
07/01/17 02:42 PM
07/01/17 02:42 PM
Joined: May 2010
Posts: 9,856
out there
spasm3 Offline
spasm3  Offline

Joined: May 2010
Posts: 9,856
out there
Originally Posted By: DNVDMAX
Debris possibly blocking orifice tube or expansion valve.


Good suggestion, especially if any " stop leak " has been added.


13 elantra 75k 5w30 QSUD
03 chevy avalanche 80k synpwr 5w30
17 mazda cx-5 9500 miles m1 0w30
Re: What are these AC pressures telling me? [Re: Chris142] #4446763
07/01/17 02:43 PM
07/01/17 02:43 PM
Joined: Oct 2014
Posts: 13,298
Canyon County Idaho
CT8 Offline
CT8  Offline

Joined: Oct 2014
Posts: 13,298
Canyon County Idaho
Originally Posted By: Chris142
Has anyone added refrigerant?
Chris is a A/C pro !! this.


2015 Ford F150 2.7
2018 Ford F350 6.2
Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446766
07/01/17 02:45 PM
07/01/17 02:45 PM
Joined: Sep 2015
Posts: 1,693
USA
mk378 Offline
mk378  Offline

Joined: Sep 2015
Posts: 1,693
USA
If the suction line from the evaporator to the compressor is not cold, you have a blockage. I think this will be a TXV system and those valves can get stuck. If stop leak has been added of course all bets are off.

If the line is cold, the air inside the car should be cold too, if it is not the heater may be reheating it.

Last edited by mk378; 07/01/17 02:46 PM.
Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446796
07/01/17 03:12 PM
07/01/17 03:12 PM
Joined: May 2016
Posts: 725
Canada
i_hate_autofraud Offline
i_hate_autofraud  Offline

Joined: May 2016
Posts: 725
Canada

As noted above, put you hand on the exposed pipes near the compressor, the large one ('return' from the evaporator under the dash)
has to be cold.

The small dia pipe off the compressor must be warm/hot.

CHECK your air blend doors & actuators in the dash, they tend to be weak or sticky and won't fully
open to the cold a/c position.

Re: What are these AC pressures telling me? [Re: i_hate_autofraud] #4446823
07/01/17 03:53 PM
07/01/17 03:53 PM
Joined: Sep 2015
Posts: 1,693
USA
mk378 Offline
mk378  Offline

Joined: Sep 2015
Posts: 1,693
USA
Originally Posted By: i_hate_autofraud


The small dia pipe off the compressor must be warm/hot.


The discharge pipe is normally hot enough to burn you, and it only gets hotter if the refrigerant charge is low, so touching it isn't advisable. It won't tell you much.

Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446842
07/01/17 04:09 PM
07/01/17 04:09 PM
Joined: Jan 2007
Posts: 833
El Oeste
HawkeyeScott Offline OP
HawkeyeScott  Offline OP

Joined: Jan 2007
Posts: 833
El Oeste
Initial plan was to add refrigerant but figured that would automatically send the high side pressures higher. Is that an incorrect assumption?

Re: What are these AC pressures telling me? [Re: HawkeyeScott] #4446857
07/01/17 04:25 PM
07/01/17 04:25 PM
Joined: Sep 2015
Posts: 1,693
USA
mk378 Offline
mk378  Offline

Joined: Sep 2015
Posts: 1,693
USA
The high side being that high, with the fans running and ambient of 85, suggests that there is plenty of refrigerant.

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