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How do I check the AC pressure on these rear AC systems I can't seem to find any information about them online. The pressures with rear AC on was around 55 psi low and 265psi high. At 80 degrees outside with about 85% humidity. And with the rear AC off the pressures are lower. Does anybody know if I'm suppose to check the pressure with the rear AC on or with the rear AC off and what should the pressure be around?
 

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At 80 degrees outside with about 85% humidity, the high side should be around 170 psi and the low side around 40 psi. You may have too much refrigerant in the system.
 

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At 80 degrees outside with about 85% humidity, the high side should be around 170 psi and the low side around 40 psi. You may have too much refrigerant in the system.
I figured the same exact thing so i recovered enough refrigerant to bring it down to that psi rating and it starting blowing hot air. Then I readded new refrigerant to bring it back to the high numbers and then it started to cool down again.
 

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If both the high/low pressures are still very high and the cooling is not good, then there may be air in the system. You'll have to evacuate the system with a vacuum pump and re-charge. It's also possible that the expansion valve is bad. If you plan to evacuate the system, then that would be a good time to replace the expansion valve if it's questionable.
 

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If both the high/low pressures are still very high and the cooling is not good, then there may be air in the system. You'll have to evacuate the system with a vacuum pump and re-charge. It's also possible that the expansion valve is bad. If you plan to evacuate the system, then that would be a good time to replace the expansion valve if it's questionable.
Which expansion valve would it be? There's two.
 

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If both the high/low pressures are still very high and the cooling is not good, then there may be air in the system. You'll have to evacuate the system with a vacuum pump and re-charge. It's also possible that the expansion valve is bad. If you plan to evacuate the system, then that would be a good time to replace the expansion valve if it's questionable.
Also when checking the pressures do I have the rear AC turned on or off? Nobody specifies this anywhere.
 

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The FSM does not state the rear AC to be turned off. It would make sense to have the back AC turned on for a comprehensive test; since under normal use both are turned on.

To answer your Question "Which expansion valve would it be? There's two.", how cold is the air coming out in the front unit and out the back unit. I would say what ever unit is not producing the proper cold air, then that unit's expansion valve might be the problem.
 

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Discussion Starter #8
The FSM does not state the rear AC to be turned off. It would make sense to have the back AC turned on for a comprehensive test; since under normal use both are turned on.

To answer your Question "Which expansion valve would it be? There's two.", how cold is the air coming out in the front unit and out the back unit. I would say what ever unit is not producing the proper cold air, then that unit's expansion valve might be the problem.
I just ordered both expansion valves they were cheap enough to not really make a difference. I have the fsm for the AC I just don't understand why they wouldn't specify whether to have it on or not I mean it's just an extra sentence😂
 

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You have to understand, the FSMs were written for trained Nissan mechanics; not for shade-tree mechanics. So some things in written diagnostics are omitted because they are simply understood. A prime example is engine removal; a lot of the little steps to be performed prior to actual removal are sometimes omitted.
 

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You have to understand, the FSMs were written for trained Nissan mechanics; not for shade-tree mechanics. So some things in written diagnostics are omitted because they are simply understood. A prime example is engine removal; a lot of the little steps to be performed prior to actual removal are sometimes omitted.
But they state literally every other tiny detail except the rear AC knob.
6556
 
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