2008 Subaru Outback 2.5XT, DDM HID 5000K, K&N, Yokohama Avid TRZ, Curt Hitch, Subaru All Weather Mats, Sirius
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68 Posts
Hey Guys,
Ever since I had my engine replaced due to an idler failure and subsequent timing belt failure, I have had an odd issue with my A/C system. The AC temperature will fluctuate from Very Cold (Dry) to Warm (and Humid) and then back to Very Cold in a cycle of every 5-15 seconds.
I know this was not the normal operation for the first several years with this car. I spent 30 days in it for a 10K mile cross country trip prior to the engine issue and my A/C never fluctuated temps.
I took it into the dealer at the end of the summer but they said it was cooling fine since the cabin would eventually reach a cool state even through the fluctuations continued
I still know this is not the original operation so I am trying to do some debug and have a few questions I could use help with.
I assume in the engine replacement they had to disconnect the A/C so I expect the system was drained and recharged. However, I'm not sure if the Refrigerant is low or is I possibly have a clogged Expansion Valve.
Does anyone know the difference between what happens with a bad expansion valve vs low refrigerant
?
My next question is specifically on Low Side/High Side pressure and the operating/switch conditions on the 3-way pressure switch. I have a a/c manifold gauge coming to me so I can check the High/Low side pressure. I rummaged through the Service Manual to get ideal pressures but I am either missing something or some of the data is wrong.
Here is the first section:
2. Refrigerant Pressure with Manifold Gauge Set
A: PROCEDURE
1) Place the vehicle in the shade and windless condition.
2) Connect the manifold gauge set.
3) Open the front windows and close all doors.
4) Open the front hood.
5) Increase the engine to 1,500 rpm.
6) Turn on the A/C switch.
7) Turn the temperature control switch to MAX COOL.
8) Put in RECIRC position.
9) Turn the blower control switch to HI.
10) Read the gauge.
Standard:
Low: 127 — 196 kPa (1.3 — 2.0 kg/cm 2, 18 — 28 psi)
High: 1,471 — 1,667 kPa (15 — 17 kg/cm2, 213 — 242 psi)
Ambient temperature: 30 — 35°C (86 — 95°F)
B: INSPECTION
Now looking at the details for the 3 way pressure Switch:
Triple switch
(Pressure switch)
Low-pressure switch
operating pressure
ON to OFF 28.4 +/-2.9 psi
OFF to ON 32.6 +3.6/–4.2 psi
High-pressure switch
operating pressure
ON to OFF 455.4 +7.25/–29.0psi
OFF to ON 369.8 +/-29.0 psi
Middle-pressure switch
operating pressure
ON to OFF 198.65+/-17.35 psi
OFF to ON 256.81+/-11.60 psi
So I'm a little confused on this process. Does this indicated if the LOW side is between 28.4 and 36.2 the Compressor will be ON (switch goes from OFF -> ON) And then if it drops Lower Than 24.6 it shuts the compressor off?
This seems to go against the earlier data that showed the 'NORMAL' range Pressure with the A/C Compressor running is 18-28PSI. it would seem to me the normal range would trigger the Low Switch and shutoff the compressor if these numbers are right.
Can someone help me understand this logic?
Ever since I had my engine replaced due to an idler failure and subsequent timing belt failure, I have had an odd issue with my A/C system. The AC temperature will fluctuate from Very Cold (Dry) to Warm (and Humid) and then back to Very Cold in a cycle of every 5-15 seconds.
I know this was not the normal operation for the first several years with this car. I spent 30 days in it for a 10K mile cross country trip prior to the engine issue and my A/C never fluctuated temps.
I took it into the dealer at the end of the summer but they said it was cooling fine since the cabin would eventually reach a cool state even through the fluctuations continued
I still know this is not the original operation so I am trying to do some debug and have a few questions I could use help with.
I assume in the engine replacement they had to disconnect the A/C so I expect the system was drained and recharged. However, I'm not sure if the Refrigerant is low or is I possibly have a clogged Expansion Valve.
Does anyone know the difference between what happens with a bad expansion valve vs low refrigerant
My next question is specifically on Low Side/High Side pressure and the operating/switch conditions on the 3-way pressure switch. I have a a/c manifold gauge coming to me so I can check the High/Low side pressure. I rummaged through the Service Manual to get ideal pressures but I am either missing something or some of the data is wrong.
Here is the first section:
2. Refrigerant Pressure with Manifold Gauge Set
A: PROCEDURE
1) Place the vehicle in the shade and windless condition.
2) Connect the manifold gauge set.
3) Open the front windows and close all doors.
4) Open the front hood.
5) Increase the engine to 1,500 rpm.
6) Turn on the A/C switch.
7) Turn the temperature control switch to MAX COOL.
8) Put in RECIRC position.
9) Turn the blower control switch to HI.
10) Read the gauge.
Standard:
Low: 127 — 196 kPa (1.3 — 2.0 kg/cm 2, 18 — 28 psi)
High: 1,471 — 1,667 kPa (15 — 17 kg/cm2, 213 — 242 psi)
Ambient temperature: 30 — 35°C (86 — 95°F)
B: INSPECTION
Now looking at the details for the 3 way pressure Switch:
Triple switch
(Pressure switch)
Low-pressure switch
operating pressure
ON to OFF 28.4 +/-2.9 psi
OFF to ON 32.6 +3.6/–4.2 psi
High-pressure switch
operating pressure
ON to OFF 455.4 +7.25/–29.0psi
OFF to ON 369.8 +/-29.0 psi
Middle-pressure switch
operating pressure
ON to OFF 198.65+/-17.35 psi
OFF to ON 256.81+/-11.60 psi
So I'm a little confused on this process. Does this indicated if the LOW side is between 28.4 and 36.2 the Compressor will be ON (switch goes from OFF -> ON) And then if it drops Lower Than 24.6 it shuts the compressor off?
This seems to go against the earlier data that showed the 'NORMAL' range Pressure with the A/C Compressor running is 18-28PSI. it would seem to me the normal range would trigger the Low Switch and shutoff the compressor if these numbers are right.
Can someone help me understand this logic?
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