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Discussion Starter · #1 ·
Hi I have a 2.5 nissan altima. The ac is acting up. It starts up just fine stays on for about 10 mins then the ac clutch disengage. The Ac Compressor is new along with the dryer and pressure switch. I filled it with 18oz of the r134a and the psi on the low and high side seem fine when the comp is engaged. I'm stumped as to why It won't re engage. When I test the pressure switch I see the 5v signal but the other 2 pins are reading nothing. Again the comp and dryer are new along with the correct amount of r134a. What should I do next. I have the guages to check pressure and a multimeter handy. if anyone has had this issue I would appreciate the info you have. Thanks in advance. (Pic is pressure while clutch is engage)
Motor vehicle Automotive lighting Gauge Measuring instrument Gas
 

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The high side pressure is way too low with the compressor running. It should be at least 150 psi at 75°F ambient temperature with the compressor clutch engaged.
I'm surprised that the clutch even engages at all.

My guess is that you have a leak somewhere in the A/C system and you haven't got enough H134A remaining in the system.
Did you replace the o-rings and lubricate them properly when you replaced the components?
 

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i doubt that the expansion valve failed. The issue is low system pressure based on your manifold gauge pressures if your compressor was actually running when you took this picture.

It makes no sense that there is no voltage at the refrigerant pressure sensor output. If that were the case, the compressor clutch would not engage. How are you measuring the output voltage of the pressure sensor? By back probing the wires with a multimeter at the IPDM or with a scan gauge connected to the OBD2 port?
 

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Discussion Starter · #6 ·
Yeah the system was vaccum sealed for a while. I was trying to prob the ipdm, I might be doing it wrong though. And yess the pressure shown above is with the comp engaged. I'll try to update with some more photos. Also to my understanding the ipdm rarely fails and is non serviceable?
 

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The IPDM is non-serviceable so would need replacement if faulty. This is not the likely cause of the problem. When / how long ago did you recharge the system with 18 oz of refrigerant? Did you have 150 psi on the high side after filling the 18 oz? Were you monitoring the low and high pressures at the time you were recharging it?
 

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Discussion Starter · #9 ·
The IPDM is non-serviceable so would need replacement if faulty. This is not the likely cause of the problem. When / how long ago did you recharge the system with 18 oz of refrigerant? Did you have 150 psi on the high side after filling the 18 oz? Were you monitoring the low and high pressures at the time you were recharging it?
I also appreciate all the help too 🙏
 

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Yes. Get some PAG 46 oil and lubricate ALL of the o-rings that you replaced on the compressor lines, the drier, and the refrigerant pressure sensor. Then reassemble everything, draw a vacuum, hold the vacuum for at least 30 minutes to be certain you don't have any leaks, and recharge until you have added the 18 oz of R134A. Monitor the low and high side pressures while doing this. Hope this works for you.
 

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Oil already present in a part will not suddenly unroll a dry o-ring which rolled on its' own body because it got installed dry............it will tend to leak then.

Charge to the highside pressure needed since sometimes you can't get the full amount of refrigerant in because the oil amount is off and very common. A LOT of people are driving around with too much oil in the system.

If you haven't learned yet to bleed a/c charging lines then learn. It does no good to vacuum down then turn around to add more air when you charge the system up.
 

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Discussion Starter · #12 ·
Hahaa I know that oil won't unroll a seal. Thing is I had no leaks when I did the uv leak test and when I pulled a vacc. I'm going to check anyways cause yes something is wrong with the high side. I will also look into excess oil in the system thanks for the suggestion.
 
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